Question

I am trying to write a regular expression string match in vb.net. The condition that I am trying to implement is that the string should contain only alphabets and must contain atleast one letter of both lower and upper case. i.e AAA-fail, aaa-fail, aAaA-pass.

The regular expression that I have come up with is ^(([a-z]+[A-Z]+)+|([A-Z]+[a-z]+)+)$

Can someone suggest some better/simpler regular expression for the same?

Answer 1

The regex you created will fail under some conditions, such as “aAb”. I think the following will work better for you:

^(?:[a-z]+[A-Z]+|[A-Z]+[a-z]+)(?:[a-zA-Z])*$