johnywhite
asked on
.NET Validation
I havve a form with a Regular Expression Validator. I am trying to get it to not allow any speical characters only letters and numbers and I also want it to not allow it to start with a number. What expression would I use and could someone also explain what the expression is doing?
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ASKER
That's what I was looking for thanks.
Regular Expression to allow alpha a first character and alpha numeric after.
^[a-zA-Z][a-zA-Z0-9]*$
Where:
^ Marks the begining of the string
[a-zA-Z] Which only allows one alpha to start the string
[a-zA-Z0-9] Which only allows one alpha numeric starting at the second character
* Quantifier Which states allow zero or more of the previous character
$ Marks the end of the string
Fernando
^[a-zA-Z][a-zA-Z0-9]*$
Where:
^ Marks the begining of the string
[a-zA-Z] Which only allows one alpha to start the string
[a-zA-Z0-9] Which only allows one alpha numeric starting at the second character
* Quantifier Which states allow zero or more of the previous character
$ Marks the end of the string
Fernando
add the $ (end of string) symbol if you dont want leading spaces or spaces within the entire string...
^[A-Za-z]+([A-Za-z]|[0-9])
^[A-Za-z]+([A-Za-z]|[0-9])
Actually the $ lets the regular expression engine know that there should be no more characters. If you do not place it there then you could have invalid characters at the end and as long as the string starts with an alpha followed by 1 or more alpha numeric it will validate.
thanks Fernando... I tested it with some leading spaces and mistakenly wrote that... your explanation covers what I was trying to say!
Good; glad we are on the same track. You have a great day. :=)
^[A-Za-z0-9]+$
Starting at the beginning of the string, replicate any number of upper-case letters, lower-case letters and numbers until the end of the string is reached.
Bob