I was dong my C# HomeWork when I fell on a little problem.
I can't fix it my self..
Who can help me with my HomeWork?
The Error I'll get with the code under here..
Use of unassigned local variable 'ValidKey'

Code:
using System;
using System.Collections.Generic;
using System.Text;

namespace Huiswerk
{
    class Program
    {
        static void ShowProfile()
        {
            Console.WriteLine("Hello World..");
        }

        static void Say(string Input)
        {
            Console.WriteLine(Input);
        }

        static void Main(string[] args)
        {
            //Declaration of Variables
            string ValidKey;
            int RandomKey = 1;
            string TempStr;
            //Start Program
            Say("Type the Following Text: ");

            switch (RandomKey)
            {
                case '1':
                    ValidKey = "qwerty";
                    break;
                case '2':
                    ValidKey = "hello";
                    break;
                case '3':
                    ValidKey = "enter";
                    break;
            }
            Say(ValidKey);
            TempStr = Console.ReadLine();
            if (TempStr == ValidKey)
            {
                Say("Welcome User..\n\t Please Enter..");
                //Show Profile
                ShowProfile();
            }
            else
            {
                Say("Invalid!!");
            }
        }
    }
}
thx already