From f5153f6c3d4797708029b88b8192201e43ff3612 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 13:38:14 +0000
Subject: [PATCH 01/13] Initial plan


From 459011be83669522a212267e0863331abb290595 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:06:28 +0000
Subject: [PATCH 02/13] Modernize AndroidApkSigner.cs with nullable reference
 types

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/AndroidApkSigner.cs                 | 40 +++++++++----------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
index 60110c478be..bb0fb5cee2a 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.IO;
@@ -14,21 +14,21 @@ public class AndroidApkSigner : JavaToolTask
 		public override string TaskPrefix => "AAS";
 
 		[Required]
-		public string ApkSignerJar { get; set; }
+		public string ApkSignerJar { get; set; } = "";
 
 		[Required]
-		public string ApkToSign { get; set; }
+		public string ApkToSign { get; set; } = "";
 
 		[Required]
-		public ITaskItem ManifestFile { get; set; }
+		public ITaskItem ManifestFile { get; set; } = null!;
 
-		public string KeyStore { get; set; }
+		public string? KeyStore { get; set; }
 
-		public string KeyAlias { get; set; }
+		public string? KeyAlias { get; set; }
 
-		public string PlatformKey { get; set; }
+		public string? PlatformKey { get; set; }
 
-		public string PlatformCert { get; set; }
+		public string? PlatformCert { get; set; }
 
 		/// <summary>
 		/// The Password for the Key.
@@ -39,7 +39,7 @@ public class AndroidApkSigner : JavaToolTask
 		///   env:<PasswordEnvironentVariable>
 		///   file:<PasswordFile>
 		/// </summary>
-		public string KeyPass { get; set; } = string.Empty;
+		public string KeyPass { get; set; } = "";
 
 		/// <summary>
 		/// The Password for the Keystore.
@@ -50,15 +50,15 @@ public class AndroidApkSigner : JavaToolTask
 		///   env:<PasswordEnvironentVariable>
 		///   file:<PasswordFile>
 		/// </summary>
-		public string StorePass { get; set; } = string.Empty;
+		public string StorePass { get; set; } = "";
 
-		public string AdditionalArguments { get; set; }
+		public string? AdditionalArguments { get; set; }
 
 		void AddStorePass (CommandLineBuilder cmd, string cmdLineSwitch, string value)
 		{
-			string pass = value.Replace ("env:", string.Empty)
-				.Replace ("file:", string.Empty)
-				.Replace ("pass:", string.Empty);
+			string pass = value.Replace ("env:", "")
+				.Replace ("file:", "")
+				.Replace ("pass:", "");
 			if (value.StartsWith ("env:", StringComparison.Ordinal)) {
 				cmd.AppendSwitchIfNotNull ($"{cmdLineSwitch} env:", pass);
 			}
@@ -87,7 +87,7 @@ protected override string GenerateCommandLineCommands ()
 			cmd.AppendSwitchIfNotNull ("-jar ", ApkSignerJar);
 			cmd.AppendSwitch ("sign");
 
-			if (!string.IsNullOrEmpty (PlatformKey) && !string.IsNullOrEmpty (PlatformCert)) {
+			if (!PlatformKey.IsNullOrEmpty () && !PlatformCert.IsNullOrEmpty ()) {
 				cmd.AppendSwitchIfNotNull ("--key ", PlatformKey);
 				cmd.AppendSwitchIfNotNull ("--cert ", PlatformCert);
 			} else {
@@ -101,7 +101,7 @@ protected override string GenerateCommandLineCommands ()
 			cmd.AppendSwitchIfNotNull ("--max-sdk-version ", maxSdk.ToString ());
 
 
-			if (!string.IsNullOrEmpty (AdditionalArguments))
+			if (!AdditionalArguments.IsNullOrEmpty ())
 				cmd.AppendSwitch (AdditionalArguments);
 
 			cmd.AppendSwitchIfNotNull (" ", ApkToSign);
@@ -129,7 +129,7 @@ protected override string ToolName {
 
 		protected override bool ValidateParameters ()
 		{
-			if (!string.IsNullOrEmpty (PlatformKey) && !string.IsNullOrEmpty (PlatformCert)) {
+			if (!PlatformKey.IsNullOrEmpty () && !PlatformCert.IsNullOrEmpty ()) {
 				if (!File.Exists (PlatformKey)) {
 					Log.LogCodedError ("XA4310", Properties.Resources.XA4310, "$(AndroidSigningPlatformKey)", PlatformKey);
 					return false;
@@ -139,15 +139,15 @@ protected override bool ValidateParameters ()
 					return false;
 				}
 			} else {
-				if (!string.IsNullOrEmpty (KeyStore) && !File.Exists (KeyStore)) {
+				if (!KeyStore.IsNullOrEmpty () && !File.Exists (KeyStore)) {
 					Log.LogCodedError ("XA4310", Properties.Resources.XA4310, "$(AndroidSigningKeyStore)", KeyStore);
 					return false;
 				}
-				if (string.IsNullOrEmpty (KeyPass)) {
+				if (KeyPass.IsNullOrEmpty ()) {
 					Log.LogCodedError ("XA4314", Properties.Resources.XA4314, "$(AndroidSigningKeyPass)");
 					return false;
 				}
-				if (string.IsNullOrEmpty (StorePass)) {
+				if (StorePass.IsNullOrEmpty ()) {
 					Log.LogCodedError ("XA4314", Properties.Resources.XA4314, "$(AndroidSigningStorePass)");
 					return false;
 				}

From 6878ee7304ad4aee266c3e36c66331cd16d1a6de Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:11:36 +0000
Subject: [PATCH 03/13] Modernize CalculateProjectDependencies and JavaToolTask
 with nullable reference types

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/CalculateProjectDependencies.cs     | 34 +++++++++----------
 .../Tasks/JavaToolTask.cs                     | 20 +++++------
 2 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
index 5e1a90b050c..8b2e02dc619 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.IO;
@@ -16,38 +16,38 @@ public class CalculateProjectDependencies : AndroidTask
 
 		const int DefaultMinSDKVersion = 11;
 
-		public string CommandLineToolsVersion { get; set; }
+		public string? CommandLineToolsVersion { get; set; }
 
-		public string AndroidApiLevel { get; set; }
+		public string? AndroidApiLevel { get; set; }
 
 		[Required]
-		public string TargetFrameworkVersion { get; set; }
+		public string TargetFrameworkVersion { get; set; } = "";
 
 		[Required]
-		public ITaskItem ManifestFile { get; set; }
+		public ITaskItem ManifestFile { get; set; } = null!;
 
 		[Required]
-		public string BuildToolsVersion { get; set; }
+		public string BuildToolsVersion { get; set; } = "";
 
-		public string PlatformToolsVersion { get; set; }
+		public string? PlatformToolsVersion { get; set; }
 
-		public string NdkVersion { get; set; }
+		public string? NdkVersion { get; set; }
 
 		public bool NdkRequired { get; set; }
 
-		public string JdkVersion { get; set; }
+		public string? JdkVersion { get; set; }
 
 		public bool GetJavaDependencies { get; set; } = false;
 
 		[Output]
-		public ITaskItem [] Dependencies { get; set; }
+		public ITaskItem []? Dependencies { get; set; }
 
 		[Output]
-		public ITaskItem[] JavaDependencies { get; set; }
+		public ITaskItem[]? JavaDependencies { get; set; }
 
 		ITaskItem CreateAndroidDependency (string include, string version)
 		{
-			if (string.IsNullOrEmpty (version))
+			if (version.IsNullOrEmpty ())
 				return new TaskItem (include);
 
 			return new TaskItem (include, new Dictionary<string, string> {
@@ -59,7 +59,7 @@ public override bool RunTask ()
 		{
 			var dependencies = new List<ITaskItem> ();
 			var javaDependencies = new List<ITaskItem> ();
-			var targetApiLevel = string.IsNullOrEmpty (AndroidApiLevel) ?
+			var targetApiLevel = AndroidApiLevel.IsNullOrEmpty () ?
 				MonoAndroidHelper.SupportedVersions.GetApiLevelFromFrameworkVersion (TargetFrameworkVersion) :
 				MonoAndroidHelper.SupportedVersions.GetApiLevelFromId (AndroidApiLevel);
 			var manifestApiLevel = DefaultMinSDKVersion;
@@ -70,16 +70,16 @@ public override bool RunTask ()
 			var sdkVersion = Math.Max (targetApiLevel.Value, manifestApiLevel);
 			dependencies.Add (CreateAndroidDependency ($"platforms/android-{sdkVersion}", $""));
 			dependencies.Add (CreateAndroidDependency ($"build-tools/{BuildToolsVersion}", BuildToolsVersion));
-			if (!string.IsNullOrEmpty (PlatformToolsVersion)) {
+			if (!PlatformToolsVersion.IsNullOrEmpty ()) {
 				dependencies.Add (CreateAndroidDependency ("platform-tools", PlatformToolsVersion));
 			}
-			if (!string.IsNullOrEmpty (CommandLineToolsVersion)) {
+			if (!CommandLineToolsVersion.IsNullOrEmpty ()) {
 				dependencies.Add (CreateAndroidDependency ($"cmdline-tools/{CommandLineToolsVersion}", CommandLineToolsVersion));
 			}
-			if (!string.IsNullOrEmpty (NdkVersion) && NdkRequired) {
+			if (!NdkVersion.IsNullOrEmpty () && NdkRequired) {
 				dependencies.Add (CreateAndroidDependency ("ndk-bundle", NdkVersion));
 			}
-			if (!string.IsNullOrEmpty (JdkVersion) && GetJavaDependencies) {
+			if (!JdkVersion.IsNullOrEmpty () && GetJavaDependencies) {
 				javaDependencies.Add (CreateAndroidDependency ("jdk", JdkVersion));
 			}
 			Dependencies = dependencies.ToArray ();
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
index b4f17917e7f..f23e338a1b4 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -79,17 +79,17 @@ at com.android.dx.command.Main.main(Main.java:106)
 		string file;
 		int line, column;
 
-		public string JavaOptions { get; set; }
+		public string? JavaOptions { get; set; }
 
-		public string JavaMaximumHeapSize { get; set; }
+		public string? JavaMaximumHeapSize { get; set; }
 
 		public virtual string DefaultErrorCode => "JAVA0000";
 
-		public string WorkingDirectory { get; set; }
+		public string? WorkingDirectory { get; set; }
 
-		public string AssemblyIdentityMapFile { get; set; }
+		public string? AssemblyIdentityMapFile { get; set; }
 
-		public string IntermediateOutputPath { get; set; }
+		public string? IntermediateOutputPath { get; set; }
 
 		protected override string ToolName {
 			get { return OS.IsWindows ? "java.exe" : "java"; }
@@ -120,7 +120,7 @@ protected override bool HandleTaskExecutionErrors ()
 
 		protected override string GetWorkingDirectory ()
 		{
-			if (!string.IsNullOrEmpty (WorkingDirectory))
+			if (!WorkingDirectory.IsNullOrEmpty ())
 				return WorkingDirectory;
 			return base.GetWorkingDirectory ();
 		}
@@ -147,14 +147,14 @@ internal virtual bool ProcessOutput (string singleLine, AssemblyIdentityMap asse
 			foreach (Match lp in lpRegex.Matches (singleLine)) {
 				var id = lp.Groups["identifier"].Value;
 				var asmName = assemblyMap.GetAssemblyNameForImportDirectory (id);
-				if (!string.IsNullOrEmpty (asmName)) {
-					var path = Path.Combine(IntermediateOutputPath ?? string.Empty, "lp", id);
+				if (!asmName.IsNullOrEmpty ()) {
+					var path = Path.Combine(IntermediateOutputPath ?? "", "lp", id);
 					mappingText.Add (string.Format (Properties.Resources.XA_Directory_Is_From, path, asmName));
 				}
 			}
 
 			if (match.Success) {
-				if (!string.IsNullOrEmpty (file)) {
+				if (!file.IsNullOrEmpty ()) {
 					Log.LogError (ToolName, DefaultErrorCode, null, file, line - 1, column + 1, 0, 0, errorText.ToString () + String.Join (Environment.NewLine, mappingText));
 					errorText.Clear ();
 					mappingText.Clear ();

From e5ea6549b68b415ddf916040ec766cd0aeb6dd24 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:16:01 +0000
Subject: [PATCH 04/13] Modernize ConvertCustomView, MergeRemapXml, and
 ImportJavaDoc with nullable reference types

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/ConvertCustomView.cs                     | 14 +++++++-------
 .../Tasks/ImportJavaDoc.cs                         | 12 ++++++------
 .../Tasks/MergeRemapXml.cs                         |  6 +++---
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
index 522732eba9d..937f47cf006 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
@@ -1,6 +1,6 @@
 // Copyright (C) 2018 Microsoft, Inc. All rights reserved.
 
-#nullable disable
+#nullable enable
 
 using System;
 using System.Diagnostics;
@@ -18,15 +18,15 @@ public class ConvertCustomView : AndroidTask {
 		public override string TaskPrefix => "CCV";
 
 		[Required]
-		public string CustomViewMapFile { get; set; }
+		public string CustomViewMapFile { get; set; } = "";
 
 		[Required]
-		public string AcwMapFile { get; set; }
+		public string AcwMapFile { get; set; } = "";
 
-		public ITaskItem [] ResourceDirectories { get; set; }
+		public ITaskItem []? ResourceDirectories { get; set; }
 
 		[Output]
-		public ITaskItem [] Processed { get; set; }
+		public ITaskItem []? Processed { get; set; }
 
 		Dictionary<string, string> _resource_name_case_map;
 		Dictionary<string, string> resource_name_case_map => _resource_name_case_map ??= MonoAndroidHelper.LoadResourceCaseMap (BuildEngine4, ProjectSpecificTaskObjectKey);
@@ -87,8 +87,8 @@ public override bool RunTask ()
 				ITaskItem resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec, StringComparison.OrdinalIgnoreCase)) ?? null;
 				var hash = resdir?.GetMetadata ("Hash") ?? null;
 				var stamp = resdir?.GetMetadata ("StampFile") ?? null;
-				var filename = !string.IsNullOrEmpty (hash) ? hash : "compiled";
-				var stampFile = !string.IsNullOrEmpty (stamp) ? stamp : $"{filename}.stamp";
+				var filename = !hash.IsNullOrEmpty () ? hash : "compiled";
+				var stampFile = !stamp.IsNullOrEmpty () ? stamp : $"{filename}.stamp";
 				Log.LogDebugMessage ($"{filename} {stampFile}");
 				output.Add (file, new TaskItem (Path.GetFullPath (file), new Dictionary<string, string> {
 					{ "StampFile" , stampFile },
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
index e0d122a1724..881102a45f8 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -14,17 +14,17 @@ public class ImportJavaDoc : AndroidDotnetToolTask
 	{
 		public override string TaskPrefix => "IJD";
 
-		public string [] JavaDocs { get; set; }
+		public string []? JavaDocs { get; set; }
 		
-		public string [] References { get; set; }
+		public string []? References { get; set; }
 
-		public string [] Transforms { get; set; }
+		public string []? Transforms { get; set; }
 
 		[Required]
-		public string TargetAssembly { get; set; }
+		public string TargetAssembly { get; set; } = "";
 
 		[Required]
-		public string OutputDocDirectory { get; set; }
+		public string OutputDocDirectory { get; set; } = "";
 
 		protected override string GenerateCommandLineCommands ()
 		{
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs b/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
index b4c50c08e16..a4d09a66643 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -18,10 +18,10 @@ public class MergeRemapXml : AndroidTask
 	{
 		public  override    string      TaskPrefix      => "MRX";
 
-		public  ITaskItem[]     InputRemapXmlFiles  { get; set; }
+		public  ITaskItem[]?     InputRemapXmlFiles  { get; set; }
 
 		[Required]
-		public  ITaskItem       OutputFile          { get; set; }
+		public  ITaskItem       OutputFile          { get; set; } = null!;
 
 		public override bool RunTask ()
 		{

From e6c3115ceb624df491f7f35cb2c5e55b3fc05801 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:20:40 +0000
Subject: [PATCH 05/13] Modernize JavaDoc and JavaSourceUtils with nullable
 reference types

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/JavaDoc.cs                          | 12 +++---
 .../Tasks/JavaSourceUtils.cs                  | 38 +++++++++----------
 2 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
index e776ede68cb..1900957d07e 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.Linq;
@@ -18,15 +18,15 @@ public class JavaDoc : JavaToolTask
 	{
 		public override string TaskPrefix => "JDC";
 
-		public string [] SourceDirectories { get; set; }
+		public string []? SourceDirectories { get; set; }
 
-		public string [] DestinationDirectories { get; set; }
+		public string []? DestinationDirectories { get; set; }
 
-		public string [] ReferenceJars { get; set; }
+		public string []? ReferenceJars { get; set; }
 
-		public string JavaPlatformJar { get; set; }
+		public string? JavaPlatformJar { get; set; }
 
-		public string [] ExtraArgs { get; set; }
+		public string []? ExtraArgs { get; set; }
 
 		protected override string ToolName {
 			get { return OS.IsWindows ? "javadoc.exe" : "javadoc"; }
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
index 8b3b2d380e4..887ad2f1e30 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
@@ -1,6 +1,6 @@
 // Copyright (C) 2012 Xamarin, Inc. All rights reserved.
 
-#nullable disable
+#nullable enable
 
 using System;
 using System.Linq;
@@ -18,28 +18,28 @@ public class JavaSourceUtils : AndroidToolTask
 		public  override    string  TaskPrefix => "JSU";
 
 		[Required]
-		public  string      JavaSourceUtilsJar          { get; set; }
+		public  string      JavaSourceUtilsJar          { get; set; } = "";
 
 		[Required]
-		public  string      JavaSdkDirectory            { get; set; }
+		public  string      JavaSdkDirectory            { get; set; } = "";
 
 		[Required]
-		public  ITaskItem[] InputFiles                  { get; set; }
+		public  ITaskItem[] InputFiles                  { get; set; } = [];
 
-		public  ITaskItem[] References                  { get; set; }
+		public  ITaskItem[]? References                  { get; set; }
 
-		public  ITaskItem[] BootClassPath               { get; set; }
+		public  ITaskItem[]? BootClassPath               { get; set; }
 
-		public  ITaskItem   JavadocCopyrightFile        { get; set; }
-		public  string      JavadocUrlPrefix            { get; set; }
-		public  string      JavadocUrlStyle             { get; set; }
-		public  string      JavadocDocRootUrl           { get; set; }
+		public  ITaskItem?   JavadocCopyrightFile        { get; set; }
+		public  string?      JavadocUrlPrefix            { get; set; }
+		public  string?      JavadocUrlStyle             { get; set; }
+		public  string?      JavadocDocRootUrl           { get; set; }
 
-		public  string      JavaOptions                 { get; set; }
+		public  string?      JavaOptions                 { get; set; }
 
-		public  string      JavaMaximumHeapSize         { get; set; }
+		public  string?      JavaMaximumHeapSize         { get; set; }
 
-		public  ITaskItem   OutputJavadocXml            { get; set; }
+		public  ITaskItem?   OutputJavadocXml            { get; set; }
 
 		string  responseFilePath;
 
@@ -79,11 +79,11 @@ protected override string GenerateCommandLineCommands ()
 
 			// Add the JavaOptions if they are not null
 			// These could be any of the additional options
-			if (!string.IsNullOrEmpty (JavaOptions)) {
+			if (!JavaOptions.IsNullOrEmpty ()) {
 				cmd.AppendSwitch (JavaOptions);
 			}
 
-			if (!string.IsNullOrEmpty (JavaMaximumHeapSize)) {
+			if (!JavaMaximumHeapSize.IsNullOrEmpty ()) {
 				cmd.AppendSwitchIfNotNull("-Xmx", JavaMaximumHeapSize);
 			}
 
@@ -136,19 +136,19 @@ string CreateResponseFile ()
 			AppendArg (response, "--output-javadoc");
 			AppendArg (response, OutputJavadocXml.ItemSpec);
 
-			if (!string.IsNullOrEmpty (JavadocCopyrightFile?.ItemSpec)) {
+			if (!JavadocCopyrightFile?.ItemSpec.IsNullOrEmpty ()) {
 				AppendArg (response, "--doc-copyright");
 				AppendArg (response, Path.GetFullPath (JavadocCopyrightFile.ItemSpec));
 			}
-			if (!string.IsNullOrEmpty (JavadocUrlPrefix)) {
+			if (!JavadocUrlPrefix.IsNullOrEmpty ()) {
 				AppendArg (response, "--doc-url-prefix");
 				AppendArg (response, JavadocUrlPrefix);
 			}
-			if (!string.IsNullOrEmpty (JavadocUrlStyle)) {
+			if (!JavadocUrlStyle.IsNullOrEmpty ()) {
 				AppendArg (response, "--doc-url-style");
 				AppendArg (response, JavadocUrlStyle);
 			}
-			if (!string.IsNullOrEmpty (JavadocDocRootUrl)) {
+			if (!JavadocDocRootUrl.IsNullOrEmpty ()) {
 				AppendArg (response, "--doc-root-url");
 				AppendArg (response, JavadocDocRootUrl);
 			}

From 9016f5c8a0d37a977d7a71e8beae2b4a6d8ec0b1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:23:34 +0000
Subject: [PATCH 06/13] Modernize StripNativeLibraries and
 LinkApplicationSharedLibraries with nullable reference types

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/LinkApplicationSharedLibraries.cs          | 12 ++++++------
 .../Tasks/StripNativeLibraries.cs                    | 10 +++++-----
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
index d06915fdb0f..9b2a75f5a13 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -27,22 +27,22 @@ sealed class Config
 		}
 
 		[Required]
-		public ITaskItem[] ObjectFiles { get; set; }
+		public ITaskItem[] ObjectFiles { get; set; } = [];
 
 		[Required]
-		public ITaskItem[] ApplicationSharedLibraries { get; set; }
+		public ITaskItem[] ApplicationSharedLibraries { get; set; } = [];
 
 		[Required]
-		public ITaskItem IntermediateOutputPath { get; set; }
+		public ITaskItem IntermediateOutputPath { get; set; } = null!;
 
 		[Required]
 		public bool DebugBuild { get; set; }
 
 		[Required]
-		public string AndroidBinUtilsDirectory { get; set; }
+		public string AndroidBinUtilsDirectory { get; set; } = "";
 
 		[Required]
-		public ITaskItem[] RuntimePackLibraryDirectories { get; set; } = Array.Empty<ITaskItem> ();
+		public ITaskItem[] RuntimePackLibraryDirectories { get; set; } = [];
 
 		[Required]
 		public bool TargetsCLR { get; set; }
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
index f40c25aedb4..3c9925099cf 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
@@ -1,4 +1,4 @@
-#nullable disable
+#nullable enable
 
 using System;
 using System.IO;
@@ -16,9 +16,9 @@ public class StripNativeLibraries : AndroidToolTask
 	{
 		public override string TaskPrefix => "SNL";
 
-		public ITaskItem [] SourceFiles { get; set; }
+		public ITaskItem []? SourceFiles { get; set; }
 
-		public ITaskItem [] DestinationFiles { get; set; }
+		public ITaskItem []? DestinationFiles { get; set; }
 
 		string triple;
 		ITaskItem source;
@@ -36,9 +36,9 @@ public override bool RunTask ()
 				destination = DestinationFiles [i];
 
 				var abi = AndroidRidAbiHelper.GetNativeLibraryAbi (source);
-				if (string.IsNullOrEmpty (abi)) {
+				if (abi.IsNullOrEmpty ()) {
 					var packageId = source.GetMetadata ("NuGetPackageId");
-					if (!string.IsNullOrEmpty (packageId)) {
+					if (!packageId.IsNullOrEmpty ()) {
 						Log.LogCodedWarning ("XA4301", source.ItemSpec, 0, Properties.Resources.XA4301_ABI_NuGet, source.ItemSpec, packageId);
 					} else {
 						Log.LogCodedWarning ("XA4301", source.ItemSpec, 0, Properties.Resources.XA4301_ABI, source.ItemSpec);

From b373e4de1dc6c11b807398a20484f70d064bc294 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:26:08 +0000
Subject: [PATCH 07/13] Phase 2: Add #nullable enable to first batch of files
 without nullable directives

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Compile.cs       | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidAdb.cs         | 4 +++-
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidMessage.cs     | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidSignPackage.cs | 4 +++-
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Compile.cs b/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Compile.cs
index 1414922aab6..48e60f21e1d 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Compile.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Compile.cs
@@ -1,4 +1,6 @@
 // Copyright (C) 2011 Xamarin, Inc. All rights reserved.
+#nullable enable
+
 using System;
 using System.Diagnostics;
 using System.IO;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidAdb.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidAdb.cs
index 8678ffc6c99..70f1c3eca50 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidAdb.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidAdb.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Android.Build.Tasks;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
@@ -34,7 +36,7 @@ protected override string GenerateFullPathToTool ()
 		protected override string GenerateCommandLineCommands ()
 		{
 			var sb = new StringBuilder ();
-			if (!string.IsNullOrEmpty (AdbTarget))
+			if (!AdbTarget.IsNullOrEmpty ())
 				sb.Append ($" {AdbTarget} ");
 			sb.AppendFormat ("{0} {1}", Command, Arguments);
 			return sb.ToString ();
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidMessage.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidMessage.cs
index 663876611f8..4364e2b8e97 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidMessage.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidMessage.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using Microsoft.Android.Build.Tasks;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidSignPackage.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidSignPackage.cs
index 3256f4bab93..949c26994df 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidSignPackage.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidSignPackage.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.IO;
 using Microsoft.Build.Framework;
@@ -152,7 +154,7 @@ protected override string ToolName
 
 		protected override bool ValidateParameters ()
 		{
-			if (!string.IsNullOrEmpty (KeyStore) && !File.Exists (KeyStore)) {
+			if (!KeyStore.IsNullOrEmpty () && !File.Exists (KeyStore)) {
 				Log.LogCodedError ("XA4310", Properties.Resources.XA4310, "$(AndroidSigningKeyStore)", KeyStore);
 				return false;
 			}

From 0a4b6a8cebb46409858775ed1599c5e534fe61e0 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:29:59 +0000
Subject: [PATCH 08/13] Phase 2: Add #nullable enable to more files without
 nullable directives

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/Aapt2LinkAssetPack.cs                           | 2 ++
 .../Tasks/AdjustJavacVersionArguments.cs                  | 2 ++
 .../Tasks/AndroidComputeResPaths.cs                       | 2 ++
 .../Tasks/AndroidCreateDebugKey.cs                        | 4 +++-
 .../Tasks/AndroidDotnetToolTask.cs                        | 8 +++++---
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidError.cs     | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidWarning.cs   | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/AndroidZipAlign.cs  | 2 ++
 .../Tasks/AppendCustomMetadataToItemGroup.cs              | 2 ++
 9 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2LinkAssetPack.cs b/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2LinkAssetPack.cs
index f4d12987062..6ced257a6e7 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2LinkAssetPack.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2LinkAssetPack.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Diagnostics;
 using System.IO;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AdjustJavacVersionArguments.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AdjustJavacVersionArguments.cs
index 4f939e7ec56..c05c93b74d1 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AdjustJavacVersionArguments.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AdjustJavacVersionArguments.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using Microsoft.Build.Utilities;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs
index 0c5ceb2ff3d..03002fac517 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs
@@ -24,6 +24,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+#nullable enable
+
 using System;
 using System.Text;
 using Microsoft.Build.Utilities;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidCreateDebugKey.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidCreateDebugKey.cs
index d8d46985dbd..92ca67a054d 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidCreateDebugKey.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidCreateDebugKey.cs
@@ -1,4 +1,6 @@
-using System;
+#nullable enable
+
+using System;
 using System.IO;
 using System.Resources;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidDotnetToolTask.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidDotnetToolTask.cs
index afdf4a5b88d..f7861c5bc6e 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidDotnetToolTask.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidDotnetToolTask.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.IO;
 using System.Runtime.InteropServices;
@@ -106,13 +108,13 @@ string FindDotnet ()
 		string FindMono ()
 		{
 			string mono = BuildEngine4.GetRegisteredTaskObjectAssemblyLocal<string> (MonoKey, Lifetime);
-			if (!string.IsNullOrEmpty (mono)) {
+			if (!mono.IsNullOrEmpty ()) {
 				Log.LogDebugMessage ($"Found cached mono via {nameof (BuildEngine4.RegisterTaskObject)}");
 				return mono;
 			}
 
 			var env = Environment.GetEnvironmentVariable ("PATH");
-			if (string.IsNullOrEmpty (env)) {
+			if (!env.IsNullOrEmpty ()) {
 				foreach (var path in env.Split (Path.PathSeparator)) {
 					if (File.Exists (mono = Path.Combine (path, "mono"))) {
 						Log.LogDebugMessage ("Found mono in $PATH");
@@ -138,7 +140,7 @@ string FindMono ()
 		protected virtual CommandLineBuilder GetCommandLineBuilder ()
 		{
 			var cmd = new CommandLineBuilder ();
-			if (!string.IsNullOrEmpty (AssemblyPath)) {
+			if (!AssemblyPath.IsNullOrEmpty ()) {
 				cmd.AppendFileNameIfNotNull (AssemblyPath);
 			}
 			return cmd;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidError.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidError.cs
index 1bb902fd4d4..6b27c8fdfca 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidError.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidError.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using Microsoft.Android.Build.Tasks;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidWarning.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidWarning.cs
index cfe946e81dc..6318ed08e18 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidWarning.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidWarning.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using Microsoft.Android.Build.Tasks;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidZipAlign.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidZipAlign.cs
index 88e27626c37..7a004263f85 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidZipAlign.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidZipAlign.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.IO;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AppendCustomMetadataToItemGroup.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AppendCustomMetadataToItemGroup.cs
index a62287637a9..af8c2fc2621 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AppendCustomMetadataToItemGroup.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AppendCustomMetadataToItemGroup.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.IO;

From ea6f239f845cef5f881a638c00eb45c6ef679cf9 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:33:26 +0000
Subject: [PATCH 09/13] Phase 2: Add #nullable enable to batch of simple files
 without string.IsNullOrEmpty patterns

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/AssemblyModifierPipeline.cs                           | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/CheckClientHandlerType.cs | 2 ++
 .../Tasks/CheckDuplicateJavaLibraries.cs                        | 2 ++
 .../Tasks/CheckForInvalidDesignerConfig.cs                      | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/CheckProjectItems.cs      | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/ClassParse.cs             | 2 ++
 .../Tasks/CollectAssemblyFilesForArchive.cs                     | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/ComputeHash.cs            | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs          | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/CopyResource.cs           | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/CreateAssemblyStore.cs    | 2 ++
 11 files changed, 22 insertions(+)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AssemblyModifierPipeline.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AssemblyModifierPipeline.cs
index 4086bde3e99..16d44eab315 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AssemblyModifierPipeline.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AssemblyModifierPipeline.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.IO;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CheckClientHandlerType.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CheckClientHandlerType.cs
index 88c02bf6c1e..0f145294382 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CheckClientHandlerType.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CheckClientHandlerType.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CheckDuplicateJavaLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CheckDuplicateJavaLibraries.cs
index dbfdf1762db..7390d256abe 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CheckDuplicateJavaLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CheckDuplicateJavaLibraries.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.IO;
 using System.Linq;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CheckForInvalidDesignerConfig.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CheckForInvalidDesignerConfig.cs
index 8168ea77c61..9f0b63874f8 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CheckForInvalidDesignerConfig.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CheckForInvalidDesignerConfig.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Android.Build.Tasks;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CheckProjectItems.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CheckProjectItems.cs
index 09fed25ca38..7e11ce062f0 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CheckProjectItems.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CheckProjectItems.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ClassParse.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ClassParse.cs
index a8a54de00f9..ece680ed7a6 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ClassParse.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ClassParse.cs
@@ -1,5 +1,7 @@
 // Copyright (C) 2012 Xamarin, Inc. All rights reserved.
 
+#nullable enable
+
 using System.IO;
 using Microsoft.Android.Build.Tasks;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CollectAssemblyFilesForArchive.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CollectAssemblyFilesForArchive.cs
index facd6437405..a9b50ac09ce 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CollectAssemblyFilesForArchive.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CollectAssemblyFilesForArchive.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ComputeHash.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ComputeHash.cs
index a23faf735ab..578fc6bbd91 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ComputeHash.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ComputeHash.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System.Collections.Generic;
 using Microsoft.Build.Utilities;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs
index 348ed69a98b..230dc69e915 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs
@@ -1,5 +1,7 @@
 // Copyright (C) 2011 Xamarin, Inc. All rights reserved.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.IO;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CopyResource.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CopyResource.cs
index 6568035f684..9aba2e7f2a4 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CopyResource.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CopyResource.cs
@@ -1,6 +1,8 @@
 // Author: Jonathan Pobst <jpobst@xamarin.com>
 // Copyright (C) 2011 Xamarin, Inc. All rights reserved.
 
+#nullable enable
+
 using System.IO;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CreateAssemblyStore.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CreateAssemblyStore.cs
index dc5dde54822..f68e99a5791 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CreateAssemblyStore.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CreateAssemblyStore.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;

From 7e5255c7288ea99c6b9ef258115010b55a59f881 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 14:34:54 +0000
Subject: [PATCH 10/13] Phase 2: Continue adding #nullable enable to more
 simple files

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/CollectDalvikFilesForArchive.cs                       | 2 ++
 .../Tasks/CreateTemporaryDirectory.cs                           | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/D8.cs                     | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CollectDalvikFilesForArchive.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CollectDalvikFilesForArchive.cs
index 94c920398e7..3ad49ddc407 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CollectDalvikFilesForArchive.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CollectDalvikFilesForArchive.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using System.IO;
 using Microsoft.Android.Build.Tasks;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CreateTemporaryDirectory.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CreateTemporaryDirectory.cs
index 26db43bc5c9..f9aa4f07e92 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CreateTemporaryDirectory.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CreateTemporaryDirectory.cs
@@ -1,5 +1,7 @@
 // Copyright (C) 2011 Xamarin, Inc. All rights reserved.
 
+#nullable enable
+
 using System;
 using System.IO;
 using Microsoft.Build.Framework;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/D8.cs b/src/Xamarin.Android.Build.Tasks/Tasks/D8.cs
index 06207bd61b2..c7c15fcf065 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/D8.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/D8.cs
@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using System.Collections.Generic;

From 7ad34ad590cae99f4964f874793b8c5e9221b769 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 16:09:06 +0000
Subject: [PATCH 11/13] Fix nullable reference type compilation errors in
 modernized MSBuild tasks

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/AndroidApkSigner.cs                 |  4 ++--
 .../Tasks/CalculateProjectDependencies.cs     |  2 +-
 .../Tasks/ConvertCustomView.cs                | 12 +++++-----
 .../Tasks/ImportJavaDoc.cs                    | 18 +++++++++------
 .../Tasks/JavaDoc.cs                          | 22 +++++++++++--------
 .../Tasks/JavaSourceUtils.cs                  |  8 ++++---
 .../Tasks/JavaToolTask.cs                     |  6 +++--
 .../Tasks/LinkApplicationSharedLibraries.cs   |  6 ++---
 .../Tasks/MergeRemapXml.cs                    | 10 +++++----
 .../Tasks/StripNativeLibraries.cs             | 10 ++++-----
 10 files changed, 56 insertions(+), 42 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
index bb0fb5cee2a..7e5f790fb8e 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
@@ -74,8 +74,8 @@ protected override string GenerateCommandLineCommands ()
 			var cmd = new CommandLineBuilder ();
 
 			var manifest = AndroidAppManifest.Load (ManifestFile.ItemSpec, MonoAndroidHelper.SupportedVersions);
-			int minSdk = MonoAndroidHelper.SupportedVersions.MinStableVersion.ApiLevel;
-			int maxSdk = MonoAndroidHelper.SupportedVersions.MaxStableVersion.ApiLevel;
+			int minSdk = MonoAndroidHelper.SupportedVersions.MinStableVersion?.ApiLevel ?? 1;
+			int maxSdk = MonoAndroidHelper.SupportedVersions.MaxStableVersion?.ApiLevel ?? 1;
 			if (manifest.MinSdkVersion.HasValue)
 				minSdk = manifest.MinSdkVersion.Value;
 
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
index 8b2e02dc619..2eb484bb40f 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/CalculateProjectDependencies.cs
@@ -67,7 +67,7 @@ public override bool RunTask ()
 				var manifest = AndroidAppManifest.Load (ManifestFile.ItemSpec, MonoAndroidHelper.SupportedVersions);
 				manifestApiLevel = manifest.TargetSdkVersion ?? manifest.MinSdkVersion ?? DefaultMinSDKVersion;
 			}
-			var sdkVersion = Math.Max (targetApiLevel.Value, manifestApiLevel);
+			var sdkVersion = Math.Max (targetApiLevel ?? DefaultMinSDKVersion, manifestApiLevel);
 			dependencies.Add (CreateAndroidDependency ($"platforms/android-{sdkVersion}", $""));
 			dependencies.Add (CreateAndroidDependency ($"build-tools/{BuildToolsVersion}", BuildToolsVersion));
 			if (!PlatformToolsVersion.IsNullOrEmpty ()) {
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
index 937f47cf006..9a6aa629e84 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs
@@ -28,7 +28,7 @@ public class ConvertCustomView : AndroidTask {
 		[Output]
 		public ITaskItem []? Processed { get; set; }
 
-		Dictionary<string, string> _resource_name_case_map;
+		Dictionary<string, string>? _resource_name_case_map;
 		Dictionary<string, string> resource_name_case_map => _resource_name_case_map ??= MonoAndroidHelper.LoadResourceCaseMap (BuildEngine4, ProjectSpecificTaskObjectKey);
 
 		public override bool RunTask ()
@@ -53,7 +53,7 @@ public override bool RunTask ()
 						bool update = false;
 						foreach (var elem in AndroidResource.GetElements (e).Prepend (e)) {
 							update |= TryFixCustomView (elem, acw_map, (level, message) => {
-								ITaskItem resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec, StringComparison.OrdinalIgnoreCase)) ?? null;
+								ITaskItem? resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec, StringComparison.OrdinalIgnoreCase));
 								switch (level) {
 								case TraceLevel.Error:
 									Log.FixupResourceFilenameAndLogCodedError ("XA1002", message, file, resdir?.ItemSpec, resource_name_case_map);
@@ -84,9 +84,9 @@ public override bool RunTask ()
 			}
 			var output = new Dictionary<string, ITaskItem> (processed.Count);
 			foreach (var file in processed) {
-				ITaskItem resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec, StringComparison.OrdinalIgnoreCase)) ?? null;
-				var hash = resdir?.GetMetadata ("Hash") ?? null;
-				var stamp = resdir?.GetMetadata ("StampFile") ?? null;
+				ITaskItem? resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec, StringComparison.OrdinalIgnoreCase));
+				var hash = resdir?.GetMetadata ("Hash");
+				var stamp = resdir?.GetMetadata ("StampFile");
 				var filename = !hash.IsNullOrEmpty () ? hash : "compiled";
 				var stampFile = !stamp.IsNullOrEmpty () ? stamp : $"{filename}.stamp";
 				Log.LogDebugMessage ($"{filename} {stampFile}");
@@ -147,7 +147,7 @@ bool TryFixFragment (XAttribute attr, Dictionary<string, string> acwMap)
 			return false;
 		}
 
-		bool TryFixCustomView (XElement elem, Dictionary<string, string> acwMap, Action<TraceLevel, string> logMessage = null)
+		bool TryFixCustomView (XElement elem, Dictionary<string, string> acwMap, Action<TraceLevel, string>? logMessage = null)
 		{
 			// Looks for any <My.DotNet.Class ...
 			// and tries to change it to the ACW name
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs b/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
index 881102a45f8..0bf10af3280 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/ImportJavaDoc.cs
@@ -37,13 +37,17 @@ protected override string GenerateCommandLineCommands ()
 			//	cmd.AppendSwitch (r);
 			cmd.AppendSwitch ("-v=2");
 			cmd.AppendSwitchIfNotNull ("--out=", OutputDocDirectory);
-			foreach (var j in JavaDocs)
-				cmd.AppendSwitchIfNotNull ("--doc-dir=", Path.GetDirectoryName (j));
-			foreach (var t in Transforms) {
-				if (t.EndsWith ("Metadata.xml", StringComparison.InvariantCultureIgnoreCase))
-					cmd.AppendSwitchIfNotNull ("--metadata=", t);
-				else
-					cmd.AppendSwitchIfNotNull ("--enum-map=", t);
+			if (JavaDocs != null) {
+				foreach (var j in JavaDocs)
+					cmd.AppendSwitchIfNotNull ("--doc-dir=", Path.GetDirectoryName (j));
+			}
+			if (Transforms != null) {
+				foreach (var t in Transforms) {
+					if (t.EndsWith ("Metadata.xml", StringComparison.InvariantCultureIgnoreCase))
+						cmd.AppendSwitchIfNotNull ("--metadata=", t);
+					else
+						cmd.AppendSwitchIfNotNull ("--enum-map=", t);
+				}
 			}
 			return cmd.ToString ();
 		}
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
index 1900957d07e..9d7b37002c9 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaDoc.cs
@@ -34,21 +34,25 @@ protected override string ToolName {
 
 		public override bool RunTask ()
 		{
-			foreach (var dir in DestinationDirectories)
-				if (!Directory.Exists (dir))
-					Directory.CreateDirectory (dir);
+			if (DestinationDirectories != null) {
+				foreach (var dir in DestinationDirectories)
+					if (!Directory.Exists (dir))
+						Directory.CreateDirectory (dir);
+			}
 
 			// Basically, javadoc will return non-zero return code with those expected errors. We have to ignore them.
-			foreach (var pair in SourceDirectories.Zip (DestinationDirectories, (src, dst) => new { Source = src, Destination = dst })) {
-				context_src = pair.Source;
-				context_dst = pair.Destination;
-				base.RunTask ();
+			if (SourceDirectories != null && DestinationDirectories != null) {
+				foreach (var pair in SourceDirectories.Zip (DestinationDirectories, (src, dst) => new { Source = src, Destination = dst })) {
+					context_src = pair.Source;
+					context_dst = pair.Destination;
+					base.RunTask ();
+				}
 			}
 			return true;
 		}
 
-		string context_src;
-		string context_dst;
+		string? context_src;
+		string? context_dst;
 
 		protected override string GenerateCommandLineCommands ()
 		{
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
index 887ad2f1e30..4809a4bac60 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaSourceUtils.cs
@@ -41,7 +41,7 @@ public class JavaSourceUtils : AndroidToolTask
 
 		public  ITaskItem?   OutputJavadocXml            { get; set; }
 
-		string  responseFilePath;
+		string?  responseFilePath;
 
 		public override bool RunTask ()
 		{
@@ -134,9 +134,11 @@ string CreateResponseFile ()
 				}
 			}
 			AppendArg (response, "--output-javadoc");
-			AppendArg (response, OutputJavadocXml.ItemSpec);
+			if (OutputJavadocXml != null) {
+				AppendArg (response, OutputJavadocXml.ItemSpec);
+			}
 
-			if (!JavadocCopyrightFile?.ItemSpec.IsNullOrEmpty ()) {
+			if (JavadocCopyrightFile?.ItemSpec != null && !JavadocCopyrightFile.ItemSpec.IsNullOrEmpty ()) {
 				AppendArg (response, "--doc-copyright");
 				AppendArg (response, Path.GetFullPath (JavadocCopyrightFile.ItemSpec));
 			}
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs b/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
index f23e338a1b4..833ea09bfbd 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/JavaToolTask.cs
@@ -76,7 +76,7 @@ at com.android.dx.command.Main.main(Main.java:106)
 		List<string> errorLines = new List<string> ();
 		StringBuilder errorText = new StringBuilder ();
 		HashSet<string> mappingText = new HashSet<string> ();
-		string file;
+		string? file;
 		int line, column;
 
 		public string? JavaOptions { get; set; }
@@ -103,7 +103,9 @@ protected override bool HandleTaskExecutionErrors ()
 		{
 			if (foundError) {
 				AssemblyIdentityMap assemblyMap = new AssemblyIdentityMap ();
-				assemblyMap.Load (AssemblyIdentityMapFile);
+				if (!AssemblyIdentityMapFile.IsNullOrEmpty ()) {
+					assemblyMap.Load (AssemblyIdentityMapFile);
+				}
 				errorText.Clear ();
 				mappingText.Clear ();
 				foreach (var line in errorLines) {
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
index 9b2a75f5a13..b50266e4318 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
@@ -21,9 +21,9 @@ public class LinkApplicationSharedLibraries : AsyncTask
 
 		sealed class Config
 		{
-			public NativeLinker Linker;
-			public List<ITaskItem> LinkItems;
-			public ITaskItem OutputSharedLibrary;
+			public NativeLinker? Linker;
+			public List<ITaskItem>? LinkItems;
+			public ITaskItem? OutputSharedLibrary;
 		}
 
 		[Required]
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs b/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
index a4d09a66643..29ba45a0905 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/MergeRemapXml.cs
@@ -36,11 +36,13 @@ public override bool RunTask ()
 			using (var writer   = XmlWriter.Create (output, settings)) {
 				writer.WriteStartElement ("replacements");
 				var seen    = new HashSet<string> (StringComparer.OrdinalIgnoreCase);
-				foreach (var file in InputRemapXmlFiles) {
-					if (!seen.Add (file.ItemSpec)) {
-						continue;
+				if (InputRemapXmlFiles != null) {
+					foreach (var file in InputRemapXmlFiles) {
+						if (!seen.Add (file.ItemSpec)) {
+							continue;
+						}
+						MergeInputFile (writer, file.ItemSpec);
 					}
-					MergeInputFile (writer, file.ItemSpec);
 				}
 				writer.WriteEndElement ();
 			}
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
index 3c9925099cf..5a168856a72 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
@@ -20,15 +20,15 @@ public class StripNativeLibraries : AndroidToolTask
 
 		public ITaskItem []? DestinationFiles { get; set; }
 
-		string triple;
-		ITaskItem source;
-		ITaskItem destination;
+		string? triple;
+		ITaskItem? source;
+		ITaskItem? destination;
 
 		public override bool RunTask ()
 		{
-			if (SourceFiles.Length != DestinationFiles.Length)
+			if (SourceFiles == null || DestinationFiles == null || SourceFiles.Length != DestinationFiles.Length)
 				throw new ArgumentException ("source and destination count mismatch");
-			if (SourceFiles == null || SourceFiles.Length == 0)
+			if (SourceFiles.Length == 0)
 				return true;
 
 			for (int i = 0; i < SourceFiles.Length; i++) {

From 69c5442eed0e245246bb001daa24d1e47fbb0a0d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 11 Jul 2025 22:15:56 +0000
Subject: [PATCH 12/13] Fix remaining 5 nullable reference type compilation
 errors

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/LinkApplicationSharedLibraries.cs                   | 2 ++
 src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
index b50266e4318..ba184b12194 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs
@@ -56,6 +56,8 @@ public override System.Threading.Tasks.Task RunTaskAsync ()
 
 		void RunLinker (Config config)
 		{
+			if (config.Linker == null || config.OutputSharedLibrary == null || config.LinkItems == null)
+				return;
 			config.Linker.Link (config.OutputSharedLibrary, config.LinkItems);
 		}
 
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
index 5a168856a72..fc753b82e71 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/StripNativeLibraries.cs
@@ -67,8 +67,8 @@ public override bool RunTask ()
 		protected override string GenerateCommandLineCommands ()
 		{
 			var cmd = new CommandLineBuilder ();
-			cmd.AppendSwitchIfNotNull ("--strip-debug ", source.ItemSpec);
-			cmd.AppendSwitchIfNotNull ("-o ", destination.ItemSpec);
+			cmd.AppendSwitchIfNotNull ("--strip-debug ", source?.ItemSpec);
+			cmd.AppendSwitchIfNotNull ("-o ", destination?.ItemSpec);
 			return cmd.ToString ();
 		}
 

From baf6a1388f15987613ebc3046b81e38f508fb455 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 14 Jul 2025 15:21:38 +0000
Subject: [PATCH 13/13] Fix AndroidApkSigner nullable SDK version handling

Co-authored-by: jonathanpeppers <840039+jonathanpeppers@users.noreply.github.com>
---
 .../Tasks/AndroidApkSigner.cs                     | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
index 7e5f790fb8e..6c3000d4986 100644
--- a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidApkSigner.cs
@@ -74,15 +74,16 @@ protected override string GenerateCommandLineCommands ()
 			var cmd = new CommandLineBuilder ();
 
 			var manifest = AndroidAppManifest.Load (ManifestFile.ItemSpec, MonoAndroidHelper.SupportedVersions);
-			int minSdk = MonoAndroidHelper.SupportedVersions.MinStableVersion?.ApiLevel ?? 1;
-			int maxSdk = MonoAndroidHelper.SupportedVersions.MaxStableVersion?.ApiLevel ?? 1;
+			int? minSdk = MonoAndroidHelper.SupportedVersions.MinStableVersion?.ApiLevel;
+			int? maxSdk = MonoAndroidHelper.SupportedVersions.MaxStableVersion?.ApiLevel;
 			if (manifest.MinSdkVersion.HasValue)
 				minSdk = manifest.MinSdkVersion.Value;
 
 			if (manifest.TargetSdkVersion.HasValue)
 				maxSdk = manifest.TargetSdkVersion.Value;
 
-			minSdk = Math.Min (minSdk, maxSdk);
+			if (minSdk.HasValue && maxSdk.HasValue)
+				minSdk = Math.Min (minSdk.Value, maxSdk.Value);
 
 			cmd.AppendSwitchIfNotNull ("-jar ", ApkSignerJar);
 			cmd.AppendSwitch ("sign");
@@ -97,8 +98,12 @@ protected override string GenerateCommandLineCommands ()
 				AddStorePass (cmd, "--key-pass", KeyPass);
 			}
 
-			cmd.AppendSwitchIfNotNull ("--min-sdk-version ", minSdk.ToString ());
-			cmd.AppendSwitchIfNotNull ("--max-sdk-version ", maxSdk.ToString ());
+			if (minSdk is not null) {
+				cmd.AppendSwitchIfNotNull ("--min-sdk-version ", minSdk.ToString ());
+			}
+			if (maxSdk is not null) {
+				cmd.AppendSwitchIfNotNull ("--max-sdk-version ", maxSdk.ToString ());
+			}
 
 
 			if (!AdditionalArguments.IsNullOrEmpty ())

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