How to check if a String contains any letter from a to z?

Question

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.

I vote to reopen the question since it isn't strictly related to a regex. — Omar, May 06 '15 at 22:09
I'd also argue that this isn't a duplicate. At least not of a duplicate of _C# Regex: Checking for “a-z” and “A-Z”_ since this question is asking wether a string contains any char a-zA-Z and the other question is asking of the string solely contains of a-zA-Z... — BTC, Sep 02 '15 at 09:51

score 113 · Answer 1 · answered Oct 14 '12 at 17:28

113

What about:

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

answered Oct 14 '12 at 17:28

Omar

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15

Note: this checks if there are any characters that are not a letter, it does not check if a string has letters in it. Simple fix: bool result = !hello.Any(x => char.IsLetter(x)); – Qwerty01 Jul 22 '14 at 15:17
9

I'm glad there's a LINQ answer here, so I don't have to use Regex. – Taylor K. Aug 13 '14 at 13:59
2

Shouldn't `!hello.Any(char.IsLetter);` also work? – Mar 25 '16 at 16:48
björn: That will return true if no character is a letter, which is not what was asked. In a somewhat related manner, the question was specifically for A-Z, a-z, althought that might not be what was really wanted. – perh Mar 30 '16 at 18:06
1

If the string has a new line "\r" or "\n" then it will return true – Dman Feb 14 '17 at 09:34
1

Works great for me! – Kbdavis07 Jun 30 '18 at 20:45
1

char.IsLetter will match any unicode characters too. not just a-z in English. – CSS Nov 11 '20 at 10:39

score 85 · Accepted Answer · edited Aug 05 '16 at 16:02

85

Replace your for loop by this :

errorCounter = Regex.Matches(yourstring,@"[a-zA-Z]").Count;

Remember to use Regex class, you have to using System.Text.RegularExpressions; in your import

edited Aug 05 '16 at 16:02

John Smith

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answered Oct 14 '12 at 17:31

Ta Duy Anh

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oh excuse me I got one more question, how to detect not only letters from a to z but also all symbols? like . , ! ? < > # $ – Hendra Anggrian Oct 14 '12 at 17:58
Careful with this regex if you have to deal with non a-z letters (chinese, etc.) – Simon Bourdeau Feb 20 '21 at 00:46

score 27 · Answer 3 · answered Oct 14 '12 at 17:23

27

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);

answered Oct 14 '12 at 17:23

Kirby

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Im sorry but it reads only if I the entire String is number, if I put number and letter it won't detect – Hendra Anggrian Oct 14 '12 at 17:56
1

The correct regex would be `Regex.IsMatch(hello, @"[a-zA-Z]");` – A-y Mar 05 '13 at 21:02

score 7 · Answer 4 · answered Oct 14 '12 at 17:22

7

You can look for regular expression

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

answered Oct 14 '12 at 17:22

Sanja Melnichuk

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I can't believe you could make it so easy! – Hendra Anggrian Oct 14 '12 at 17:37
2

instead this can also be use: `(?i)^[a-z]+$`, Here `?i` makes it case insensitive. – NeverHopeless Nov 12 '12 at 12:59

score 4 · Answer 5 · answered Oct 14 '12 at 17:24

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.

score 3 · Answer 6 · answered Oct 14 '12 at 17:23

3

Use regular expression no need to convert it to char array

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

answered Oct 14 '12 at 17:23

Anirudha

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How to check if a String contains any letter from a to z?

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