Question

This works perfectly, except that when the user enters an number with a decimal (e.g. 2.3), it returns the same statement (“Number must be an integer”).

I am trying to say if it is not an int OR a double.

Code:

while (true)
{
  Console.Write("Enter First Integer:");
  string line = Console.ReadLine();

  if (!int.TryParse(line, out firstNo)) //INT OR A DOUBLE
    Console.WriteLine("Number must be an integer. {0} is not an integer.", line);
  break;
}

Answer 1

Parse it as double, it would work both with integers and decimals:

   double doubleVar;
   while (true)
   {
       Console.Write("Enter First number:");
       string line = Console.ReadLine();

       if (!double.TryParse(line, out doubleVar)) //PARSE INT OR DOUBLE
           Console.WriteLine("you must enter a number. {0} is not a number.", line);
       else
           break;
   }

Remember that . or , separator may differ depending on your current culture.

So, if you need to separate int ans doubles, do smth like this:

    if (int.TryParse(line, out intVar)) //PARSE INT
    {
          //it's int
    }
    else if (double.TryParse(line, out doubleVar)) //PARSE DOUBLE
    {
          //it's double  
    }
    else
    {
         //it's not
    }