how to check string contains only digits in c# code example

Example 1: c# check if string is only letters and numbers

if (textVar.All(c => Char.IsLetterOrDigit(c))) {
    // String contains only letters & numbers
}

Example 2: c# how do you check if a string contains only digits

if (str.All(char.IsDigit)) {
  Console.WriteLine("This string only contains numbers");
}