DynamicMethodFromExpressionWithClosure

DynamicMethodFromExpressionWithClosure.cs

using System;
using System.Linq.Expressions;
					
public class Program
{
	public static void Main()
	{
		var p = new Program();
		
		var expr = p.GetNExpr();
		var binExpr = expr.Body as BinaryExpression;
		// Console.WriteLine(binExpr);
		
		var xExpr = binExpr.Left as MemberExpression;
		//Console.WriteLine(xExpr);
		
		var closureExpr = xExpr.Expression as ConstantExpression;
		var closureValue = closureExpr.Value;
		//Console.WriteLine(closureValue);
		
		var closureType = xExpr.Member.DeclaringType;
		//Console.WriteLine(closureType);
		
		var dynMethod = new System.Reflection.Emit.DynamicMethod(
			string.Empty, 
			typeof(int), 
			new Type[] { closureType },
			closureType,
			true);
			
		var il = dynMethod.GetILGenerator();
		il.Emit(System.Reflection.Emit.OpCodes.Ldarg_0);
	
		var xField = closureType.GetField("x");
		il.Emit(System.Reflection.Emit.OpCodes.Ldfld, xField);
		
		il.Emit(System.Reflection.Emit.OpCodes.Ldarg_0);
		
		var yField = closureType.GetField("y");
		il.Emit(System.Reflection.Emit.OpCodes.Ldfld, yField);
			
		il.Emit(System.Reflection.Emit.OpCodes.Add);
		il.Emit(System.Reflection.Emit.OpCodes.Ret);
		
		var invokeDynMethod = (Func<int>)dynMethod.CreateDelegate(
			typeof(Func<int>), 
			closureValue
		);
		
		var sum = invokeDynMethod();
		Console.WriteLine(sum);
	}
	
	public Expression<Func<int>> GetNExpr() {
		var x = 1;
		var y = 2;
		return () => x + y;
	}
	
	int x = 1;
	int y = 2;
	public int GetN() {
		return x + y;
	}
}