Why has a lambda with no capture changed from a static in C# 5 to an instance method in C# 6?

Question

This code throws an exception on the marked line:

using System;
using System.Linq.Expressions;

namespace ConsoleApplication2
{
    class Program
    {
              


        

Answer 1

I don't have an answer as to why that is so (reproduced locally, too).

However, the answer to:

Why is it so? How can this be avoided so that Expression.Call would begin to work again in new Visual Studio?

You can do this (works on both compilers):

Action a = (x, y) => Console.WriteLine(x + y);

ParameterExpression p1 = Expression.Parameter(typeof(int), "p1");
ParameterExpression p2 = Expression.Parameter(typeof(int), "p2");

MethodCallExpression call;
if (a.Method.IsStatic)
{
    call = Expression.Call(a.Method, p1, p2);
}
else
{
    call = Expression.Call(Expression.Constant(a.Target), a.Method, p1, p2);
}

Thanks to Jeppe Stig Nielsen for fix regarding a.Target