通过正则表达式验证文件类型

Your regex seems a bit too complex in my opinion. Also, remember that the dot is a special character meaning "any character". The following regex should work (note the escaped dots):

^.*\.(jpg|JPG|gif|GIF|doc|DOC|pdf|PDF)$

You can use a tool like Expresso to test your regular expressions.

Are you just looking to verify that the file is of a given extension? You can simplify what you are trying to do with something like this:

(.*?)\.(jpg|gif|doc|pdf)$

Then, when you call IsMatch() make sure to pass RegexOptions.IgnoreCase as your second parameter. There is no reason to have to list out the variations for casing.

Edit: As Dario mentions, this is not going to work for the RegularExpressionValidator, as it does not support casing options.

Your regexp seems to validate both the file name and the extension. Is that what you need? I'll assume it's just the extension and would use a regexp like this:

\.(jpg|gif|doc|pdf)$

And set the matching to be case insensitive.

You can embed case insensitity into the regular expression like so:

\.(?i:)(?:jpg|gif|doc|pdf)$

^.+\.(?:(?:[dD][oO][cC][xX]?)|(?:[pP][dD][fF]))$

Will accept .doc, .docx, .pdf files having a filename of at least one character:

^           = beginning of string
.+          = at least one character (any character)
\.          = dot ('.')
(?:pattern) = match the pattern without storing the match)
[dD]        = any character in the set ('d' or 'D')
[xX]?       = any character in the set or none
('x' may be missing so 'doc' or 'docx' are both accepted)
|           = either the previous or the next pattern
$           = end of matched string

Warning! Without enclosing the whole chain of extensions in (?:), an extension like .docpdf would pass.

You can test regular expressions at http://www.regextester.com/

You can use this template for every file type:

ValidationExpression="^.+\.(([pP][dD][fF])|([jJ][pP][gG])|([pP][nN][gG])))$"

for ex: you can add ([rR][aA][rR]) for Rar file type and etc ...