using System;

using System.Linq.Expressions;

public class Program

{

    public static void Main()

    {

        (new {}).RunExpressions<object>(); //"Implementation 2"

        (new {}).RunExpressions<object>(a => a); //"Implementation 1"

        (new {}).RunExpressions<object>(a => a, b => b); //"Implementation 2"

        Extensions.RunExpressions<object>(new {}, a => a); //"Implementation 1"

        Extensions.SayHello("Marta"); //"Hello1 Marta"

    }

}

​

public static class Extensions

{

    public static void RunExpressions<T>(this object o, Expression<Func<T, object>> expression)

    {

        Console.WriteLine("Implementation 1");

    }

    public static void RunExpressions<T>(this object o, params Expression<Func<T, object>>[] expressions)

    {

        Console.WriteLine("Implementation 2");

    }

    public static void SayHello(string s)

    {

        Console.WriteLine("Hello1 " + s);   

    }

    public static void SayHello(params string[] s)

    {

        Console.WriteLine("Hello2 " + s[0]);    

    }

}