使用“ if”在C＃中给出自定义错误消息

Question

I have just started to learn how to programm using c# I am usin visual studio 2013 and I dont know the version of c#

Here I have a code to paint the background of command application

        for (; ; )
        {
            Console.WriteLine("Give a number to select a colour between 0-15? ");
            ConsoleColor renk;
            renk = (ConsoleColor)Convert.ToInt32(Console.ReadLine());




            Console.BackgroundColor = renk;
            Console.Clear();
        }

The thing is, when user gives any color, it paints the background, and loops to the start, so the user can type new one(number)

BUT

When the user just dont type a number and press enter, it just gives an error and crashes. How can I show a message and loop it to the start, when the user don't give a number?

I've tried this;

               if(renk)
            {

                Console.WriteLine("My error message!");

            }

But I don't know how to define "if "renk" is not defined" Like, if I was trying to work this code when "renk" is < 5 then I'd write;

         if(renk<5)
            {

                Console.WriteLine("My error message!");

            }


       else
            {

                bla bla bla

            }

Answer 1

Use int.TryParse for checking string number inputs.
You will enter the "if" only if a number was inputted(and you will have the number in the num var).

for (; ; )
{
       Console.WriteLine("Give a number to select a colour between 0-15? ");
       ConsoleColor renk;
       int num;
       string strNum = Console.ReadLine();
       if(int.TryParse(strNum, out num) && (num >= 0 && num <= 15))
       {
            Console.BackgroundColor = (ConsoleColor)num;
            Console.Clear();
       }
       else
       {
             Console.WriteLine("Error");
       }  
}

Answer 2

int inputNumber = 0;
for (; ; )
{
    Console.WriteLine("Give a number to select a colour between 0-15? ");
    ConsoleColor renk;

    if(int.TryParse(Console.ReadLine(),out inputNumber) && (inputNumber>=0 && inputNumber<=15))
    {
        renk = (ConsoleColor)Convert.ToInt32(inputNumber);
        Console.BackgroundColor = renk;
        Console.Clear();
    }
    else
    {
        Console.WriteLine("No Input Received! Quitting!");
        break;
    }
}