I have a case where i need to allow Alphanumeric but 1st letter of the string should always be Alphabet only
Below is sample case
string text1 = "A1222"; Valid
string text2 = "1A22"; // Invalid
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Why would you need regex for this? – Josip Juros Jun 13 '22 at 08:05
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1Please show us the code for your latest attempt and where you got stuck, so that we can tailor the answer to be most helpful and educational for you. – Heinzi Jun 13 '22 at 08:06
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3`^[a-zA-Z][a-zA-Z\d]*$` – Johnathan Barclay Jun 13 '22 at 08:06
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`IsLetter()` Does not work or you just havent tried anything and want us to do this for you? – Josip Juros Jun 13 '22 at 08:06
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@Josip i need in Data Annotation for Model validation – Zahid Mustafa Jun 13 '22 at 08:08
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@ZahidMustafa what? – Josip Juros Jun 13 '22 at 08:09
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1^[a-zA-Z][a-zA-Z\d]*$ this is what i needed Thanks – Zahid Mustafa Jun 13 '22 at 08:10
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Related answer you might find useful [RegularExpressionAttribute - How to make it not case sensitive for client side validation?](https://stackoverflow.com/questions/4218836/regularexpressionattribute-how-to-make-it-not-case-sensitive-for-client-side-v). Since you question does not mention Data Annotation I am linking it into the comments only ;-) – Cleptus Jun 13 '22 at 08:55
1 Answers
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A variant of what was already said in the comments would be
Regex reg = new Regex(@"^[a-z][a-z\d]*$", RegexOptions.IgnoreCase);
That one is not particularly complex, but for complex ones it is very nice making them case insensitive.
Warning: Do note that [A-z] would yield wrong results as mentioned in this related question Difference between regex [A-z] and [a-zA-Z]
Cleptus
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