How to make sure that a 4 number input is 4 getting numbers?

Question

My input is a year in 4 digits between 1900-3000. So the input has to be 4 digits 1994, 2022,2950.

However, how do I check if the input is only 3 digits or less or 5 digigts or more? I have alread made an if statement if it's over 1900 or 3000.

   if (YearNumb<1900 || YearNumb>3000)
        {
            Console.WriteLine("Du angav inte ett år mellan 1900 och 3000.");
            Console.ReadLine();
            return;

Answer 1

if (YearNumb<1900 || YearNumb>3000)
        {
            Console.WriteLine("Du angav inte ett år mellan 1900 och 3000.");
            Console.ReadLine();
            return;
        }
else if (YearNumb.ToString().Length != 4)
           {
            Console.WriteLine("text");
            Console.ReadLine();
            return;
        } 

Convert to string and check length.