using System;

using System.Linq.Expressions;

using FastExpressionCompiler;

using System.Reflection;

public class Program

{

    public static void Main()

    {

        TestString();

    }

    public static MethodInfo MethodOf(Expression<Func<object>> func)

    {

        var mi = GetMemberInfo(func);

        return mi is PropertyInfo ? ((PropertyInfo)mi).GetGetMethod() : (MethodInfo)mi;

    }

    public static MemberInfo GetMemberInfo(LambdaExpression func)

    {

        var ex = func.Body;

        if (ex is UnaryExpression)

            ex = ((UnaryExpression)ex).Operand;

        if (ex.NodeType == ExpressionType.New)

            return ((NewExpression)ex).Constructor;

        return

            ex is MemberExpression ? ((MemberExpression)ex).Member :

            ex is MethodCallExpression ? ((MethodCallExpression)ex).Method : (MemberInfo)((NewExpression)ex).Constructor;

    }

    public static TReturn InnerCall<TReturn>(TReturn input)

    {

        return input; // here we would do some transformation

    }

    static MethodInfo _toStringMethod = MethodOf(() => default(object).ToString());

    static MethodInfo _innerMethod = MethodOf(() => Program.InnerCall<int>(default(int))).GetGenericMethodDefinition();

    public static void TestString()

    {

        var param = Expression.Parameter(typeof(Test), "x");

        var predicate = Expression.Lambda<Func<Test, Test>>(

            Expression.MemberInit(

                Expression.New(typeof(Test)),

                Expression.Bind(typeof(Test).GetProperty("Name"),

                    Expression.Call(

                        Expression.Call(

                            _innerMethod.MakeGenericMethod(typeof(int)),

                            Expression.Property(param, "Id")

                        ),

                        _toStringMethod

                    )

                )

            )

            ,

            param

        );

        // build

        var fn = predicate.Compile();

        var ffn = predicate.CompileFast();

        // test

        var entity = new Test();

        var fnRes = fn(entity);

        var ffnRes = ffn(entity);

        Console.WriteLine("TestString(): OK!");

    }

​

    public class Test

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public Test()

        {

            Id = 1;

        }

    }

}

​