using System;

using System.Linq.Expressions;

using System.Reflection;

using System.Collections.Generic;

public class Program

{

    private static void GetDefinitionFromExpression<TConf, TArg>(

            Expression<Func<TConf, TArg>> getExpr)

        {

            var body = getExpr.Body as MemberExpression;

            if (body != null && body.NodeType == ExpressionType.MemberAccess)

            {

                var prop = (PropertyInfo)(body).Member;

                Console.WriteLine(prop.Name);

                return;

            }

​

            var methodBody = getExpr.Body as MethodCallExpression;

            if (methodBody != null && methodBody.NodeType == ExpressionType.Call)

            {

                var getter = methodBody.Method;

​

                // Special case for Indexers. Method must be a "special name"

                // and begin with "get_".

                if (!getter.Name.StartsWith("get_") && getter.IsSpecialName)

                {

                    throw new InvalidOperationException(

                        "The only method call expressions allowed are indexer-gets.");

                }

​

                var setMethodName = "set" + getter.Name.Substring("get".Length);

​

                var declaringType = getter.DeclaringType;

                if (declaringType == null)

                {

                    throw new InvalidOperationException(String.Format(

                        "Cannot find declaring type for getter {0}.",

                        getter.Name));

                }

​

                var setter = declaringType.GetTypeInfo().GetMethod(setMethodName);

​

                object name;

                var arg = methodBody.Arguments[0];

                if (arg is ConstantExpression)

                {

                    // Try to grab the value of the first argument.

                    // Works best for dict indexers (dict["key"]).

                    name = (arg as ConstantExpression).Value;

                }

                else

                {

                    // Go nuclear. Evaluate the first argument (even

                    // if it contains method calls) and assign the name

                    // to the argument's string value.

                    name = Expression

                        .Lambda(arg)

                        .Compile()

                        .DynamicInvoke();

                }

​

                Console.WriteLine($"Name: {name}");

                return;

                //return new IndexerValueStore(name.ToString(), name, getter, setter, converters);

            }

​

            throw new InvalidOperationException();

        }

    public static void Main()

    {

        GetDefinitionFromExpression<DateTime, int>(dt => dt.Day);

        GetDefinitionFromExpression<Dictionary<string, string>, string>(dict => dict["hello world"]);

    }

}