如何在C＃中没有特殊字符或数字的情况下用字母（az）询问用户输入

Question

I am trying to create a program that requires me to put a validation on the user inputs to only accept letters in a given array of 5. So basically if i am the user i am not allowed to input numbers or special characters, and if i do, i would get an error. Can someone help me out with this? I have tried various searches around and i have not been able to find a solution. I appreciate any help that i can get. This is what i have so far.

class Program
{
    static void Main(string[] args)
    {
        char[] arr = new char[5];

        //User input
        Console.WriteLine("Please Enter 5 Letters only: ");

        for (int i = 0; i < arr.Length; i++)
        {
            arr[i] = Convert.ToChar(Console.ReadLine());
        }
        //display
        for(int i = 0; i<arr.Length; i++)
        {
            Console.WriteLine("You have entered the following inputs: ");
            Console.WriteLine(arrArray[i]);
        }
    }
}

Answer 1

 char[] arr = new char[5];

            //User input
            Console.WriteLine("Please Enter 5 Letters only: ");
            string s = "abcdefghijklmnopqrstuvwxyz";
            for (int i = 0; i < arr.Length;)
            {
                string sChar = Console.ReadLine().ToLower();
                if (s.Contains(sChar) && sChar.Length == 1)
                {
                    arr[i] = Convert.ToChar(sChar);
                    i++;
                }
                else
                {
                    Console.WriteLine("Please enter a character from A-Z");
                    continue;
                }
            }
            //display
            for (int i = 0; i < arr.Length; i++)
            {
                Console.WriteLine("You have entered the following inputs: ");
                Console.WriteLine(arr[i]);
            }

Answer 2

I suggest using a Regular Expression(Regex) for that.

For numbers and letters, the correct Regex is:

string numbersLettersRegex = @"^[a-zA-Z0-9\_]+$"

Then, you just check against that Regex:

if (Regex.isMatch(numbersLettersRegex, arr[i] 
{ 
    //do stuff
}

else 
{
    //print error Message
}

Answer 3

pass your string you're trying to validate in to this func:

public bool checkYo(String myString)
{
    return Regex.IsMatch(myString, @"^[a-zA-Z]+$");
}

this will check az and AZ.. if you want just az, just get rid of the AZ part from the above function. hope this helps.

Answer 4

Try this

static void Main(string[] args) {

char[] arr = new char[5];
Console.WriteLine("Please Enter 5 Letters only: ");
string inputstring = Console.ReadLine();

if (Regex.IsMatch(inputstring, @"^[a-zA-Z]+$"))
{
    arr = inputstring.ToCharArray();
    Console.WriteLine("You have entered the following inputs: ");

    //display
    for (int i = 0; i < arr.Length; i++)
    {
        Console.Write(arr[i]);
    }
    Console.ReadLine();
}
else
{
    Console.WriteLine("Enter valid inputs and try again");
    Console.ReadLine();
}

}