using System;

using System.Linq.Expressions;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("****************** C# Equivalent Output **************************\n\n");

        int value = 4;

​

        switch (value)

        {

            case 1:

                Console.WriteLine("First Case");

                break;

            case 2:

                Console.WriteLine("Second Case");

                break;

            case 3:

                Console.WriteLine("Third Case");

                break;

            default:

                Console.WriteLine("Default Case");

                break;

        }

        Console.WriteLine("\n\n***************** Expression Tree Output **************************\n\n");

        ConstantExpression switchValue = Expression.Constant(4);

​

        var defaultCase = WriteLineExpression("Default Case");

        var case1 = WriteLineExpression("First Case");

        var case2 = WriteLineExpression("Second Case");

        var case3 = WriteLineExpression("Third Case");

​

        // This expression represents a switch statement 

        // that has a default case.

        SwitchExpression switchExpr =

            Expression.Switch(

                switchValue,

                defaultCase,

                new SwitchCase[]

                {

                    Expression.SwitchCase(case1,Expression.Constant(1)),

                    Expression.SwitchCase(case2,Expression.Constant(2)),

                    Expression.SwitchCase(case3,Expression.Constant(3))

                }

            );

​

        Expression.Lambda<Action>(switchExpr).Compile()();

    }

    public static Expression WriteLineExpression(string s)

    {

        return Expression.Call(null,

            typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),

            Expression.Constant(s));

    }

}