c# only letters
bool result = input.All(Char.IsLetter);
bool result = input.All(Char.IsLetterOrDigit);
bool result = input.All(c=>Char.IsLetterOrDigit(c) || c=='_');
// Instantiate random number generator.
private readonly Random _random = new Random();
// Generates a random number within a range.
public int RandomNumber(int min, int max)
{
return _random.Next(min, max);
}
if (str.All(char.IsDigit)) {
// String only contains numbers
}