Check out example codes for "how to check that string has only alphabet in c#". It will help you in understanding the concepts better.

Code Example 1

Regex.IsMatch(input, @"^[a-zA-Z0-9_]+$");

Code Example 2

Regex.IsMatch(input, @"^[a-zA-Z0-9]+$");

Code Example 3

Regex.IsMatch(input, @"^[a-zA-Z]+$");

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