[c#] How to check if a String contains any letter from a to z?

Possible Duplicate:
C# Regex: Checking for “a-z” and “A-Z”

I could just use the code below:

String hello = "Hello1";
Char[] convertedString = String.ToCharArray();
int errorCounter = 0;
for (int i = 0; i < CreateAccountPage_PasswordBox_Password.Password.Length; i++) {
    if (convertedString[i].Equals('a') || convertedString[i].Equals('A') .....
                            || convertedString[i].Equals('z') || convertedString[i].Equals('Z')) {
        errorCounter++;
    }
}
if(errorCounter > 0) {
    //do something
}

but I suppose it takes too much line for just a simple purpose, I believe there is a way which is much more simple, the way which I have not yet mastered.

What about:

//true if it doesn't contain letters
bool result = hello.Any(x => !char.IsLetter(x));

You can look for regular expression

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

Use regular expression no need to convert it to char array

if(Regex.IsMatch("yourString",".*?[a-zA-Z].*?"))
{
errorCounter++;
}

You could use RegEx:

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

If you don't like that, you can use LINQ:

hello.All(Char.IsLetter);

Or, you can loop through the characters, and use isAlpha:

Char.IsLetter(character);

For a minimal change:

for(int i=0; i<str.Length; i++ )
   if(str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z')
      errorCount++;

You could use regular expressions, at least if speed is not an issue and you do not really need the actual exact count.