Is Alpha Numeric, Checks if string is numbers and letters - CSharp System

Description

Is Alpha Numeric, Checks if string is numbers and letters

Demo Code

using System.Text.RegularExpressions;
using System.Text;
using System.Globalization;
using System.Collections.Generic;
using System;//from   w  ww .j  a va 2s .c om

public class Main{
        //Checks if string is numbers and letters
        //Test1254 -> True
        //$chool! -> False
        public static bool IsAlphaNumeric(string input)
        {
            char currentLetter;
            for (int i = 0; i < input.Length; i++)
            {
                currentLetter = input[i];

                if (!(Convert.ToInt32(currentLetter) >= 48 && Convert.ToInt32(currentLetter) <= 57) &&
                    !(Convert.ToInt32(currentLetter) >= 65 && Convert.ToInt32(currentLetter) <= 90) &&
                    !(Convert.ToInt32(currentLetter) >= 97 && Convert.ToInt32(currentLetter) <= 122))
                {
                    //Not a number or a letter
                    return false;
                }
            }
            return true;
        }
}

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