converting string to function in c#

gistfile1.cs

public static class Expressions
{

	static string code = @"
        public static class __CompiledExpr__
        {{
            public static {0} Run({1})
            {{
                return {2};
            }}
        }}
        ";

	static MethodInfo ToMethod(string expr, Type[] argTypes, string[] argNames, Type resultType)
	{
		StringBuilder argString = new StringBuilder();
		for (int i = 0; i < argTypes.Length; i++)
		{
			if (i != 0) argString.Append(", ");
			argString.AppendFormat("{0} {1}", argTypes[i].FullName, argNames[i]);
		}
		string finalCode = string.Format(code, resultType != null ? resultType.FullName : "void",
			argString, expr);

		var parameters = new CompilerParameters();
		parameters.ReferencedAssemblies.Add("mscorlib.dll");
		parameters.ReferencedAssemblies.Add(Path.GetFileName(Assembly.GetExecutingAssembly().Location));
		parameters.GenerateInMemory = true;

		var c = new CSharpCodeProvider();
		CompilerResults results = c.CompileAssemblyFromSource(parameters, finalCode);
		var asm = results.CompiledAssembly;
		var compiledType = asm.GetType("__CompiledExpr__");
		return compiledType.GetMethod("Run");
	}

	static Action ToAction(this string expr)
	{
		var method = ToMethod(expr, new Type[0], new string[0], null);
		return () => method.Invoke(null, new object[0]);
	}

	static Func<TResult> ToFunc<TResult>(this string expr)
	{
		var method = ToMethod(expr, new Type[0], new string[0], typeof(TResult));
		return () => (TResult)method.Invoke(null, new object[0]);
	}

	static Func<T, TResult> ToFunc<T, TResult>(this string expr, string arg1Name)
	{
		var method = ToMethod(expr, new Type[] { typeof(T) }, new string[] { arg1Name }, typeof(TResult));
		return (T arg1) => (TResult)method.Invoke(null, new object[] { arg1 });
	}

	public static Func<T1, T2, TResult> ToFunc<T1, T2, TResult>(this string expr, string arg1Name, string arg2Name)
	{
		var method = ToMethod(expr, new Type[] { typeof(T1), typeof(T2) },
			new string[] { arg1Name, arg2Name }, typeof(TResult));
		return (T1 arg1, T2 arg2) => (TResult)method.Invoke(null, new object[] { arg1, arg2 });
	}

	static Func<T1, T2, T3, TResult> ToFunc<T1, T2, T3, TResult>(this string expr, string arg1Name, string arg2Name, string arg3Name)
	{
		var method = ToMethod(expr, new Type[] { typeof(T1), typeof(T2), typeof(T3) },
			new string[] { arg1Name, arg2Name, arg3Name }, typeof(TResult));
		return (T1 arg1, T2 arg2, T3 arg3) => (TResult)method.Invoke(null, new object[] { arg1, arg2, arg3 });
	}
}