Dahomey.ExpressionEvaluator

Evaluate C# Formulas at Runtime

Supported Platforms

• .Net Standard 2.0. Compatible with
  • .Net Core 2.0+
  • .Net Framework 4.6.1+
  • Unity 2018.1+

Dahomey.ExpressionEvaluator code does not trigger any AOT complilation. It means it can be used safely with Unity IL2CPP.

Installation

NuGet

https://www.nuget.org/packages/Dahomey.ExpressionEvaluator/

Install-Package Dahomey.ExpressionEvaluator

Compilation from source

1. dotnet restore
2. dotnet pack -c Release

Examples

Parse a numeric expression

ExpressionParser parser = new ExpressionParser();
parser.RegisterVariable<int>("a");
INumericExpression expr = parser.ParseNumericExpression("1 + a");

int a = 2;
double result = expr.Evaluate(new Dictionary<string, object> { { "a", a } });
Console.WriteLine(result);

The result will be:

3

Parse a numeric expression with member access

class A
{
    public B B { get; set; }
}

class B
{
    public int Id { get; set; }
}

ExpressionParser parser = new ExpressionParser();
parser.RegisterVariable<A>("a");
INumericExpression expr = parser.ParseNumericExpression("1 + a.B.Id");

A a = new A { B = new B { Id = 12 } };
double result = expr.Evaluate(new Dictionary<string, object> { { "a", a } });
Console.WriteLine(result);

The result will be:

13

Parse a numeric expression with array or list access

ExpressionParser parser = new ExpressionParser();
parser.RegisterVariable<List<int>>("a");
INumericExpression expr = parser.ParseNumericExpression("1 + a[1]");

List<int> a = new List<int> { 1, 2 };
double result = expr.Evaluate(new Dictionary<string, object> { { "a", a } });
Console.WriteLine(result);

The result will be:

3

Parse a numeric expression with function access

Func<double, double> func = n => Math.Cos(n);
ExpressionParser parser = new ExpressionParser();
parser.RegisterFunction("cos", func);
INumericExpression expr = parser.ParseNumericExpression("1 + cos(12)");

double result = expr.Evaluate()
Console.WriteLine(result);

The result will be:

1.8438539587324922