CODEWITHSUNDEEP
regexvb.net
Wompguinea
Wompguinea

Reputation: 378

Regex rejects every email

I am using the following code in my "Continue" button to check an email address text field.

        If Regex.IsMatch(txtEmail.Text, "^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@)) (?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$",
             (RegexOptions.IgnoreCase)) Then
        pnlInvalidEmail.Visible = False
    Else
        pnlInvalidEmail.Visible = True
        Exit Sub
    End If

The problem I am having is that the Regex (pinched from here) is checking the textbox, but nothing is passing the check. No matter what I put in the text field, it fails the check and my warning panel appears.

Where am I going wrong? Apart from trying to validate emails using regex?

Upvotes: 0

Views: 36

Answers (3)

user557597
user557597

Reputation:

Must be a custom email regex. I won't try to give you a better one,
but will try to help you understand why its not letting anything through.

If you focus on this section
you can see the problem. Basically this assertion (?<= [0-9a-z] ) only lets one form in -
a single alphanum char then the @ symbol. 

   |  (?:
           (?:
                [0-9a-z] 
                (?:
                     (?:
                          \.
                          (?! \. )
                     )
                  |  [-!#\$%&'\*\+/=\?\^`\{\}\|~\w] 
                )*
           )
           (?<= [0-9a-z] )
           @
      )

And clearly from the regex conditionals, they allow matching ".."@ and [..]@ as well.
Just using another vanilla regex won't allow that.

Upvotes: 0

Federico Piazza
Federico Piazza

Reputation: 30995

I would change your regex since it's really difficult to troubleshoot it.

I would use another regex like:

^\w+[.\w]*@\w+([.]\w+)([.][a-z]{2,3})?$

Regular expression visualization

Working demo

Upvotes: 3

Amnesh Goel
Amnesh Goel

Reputation: 2655

Try this..

"^[_a-z0-9-]+(.[a-z0-9-]+)@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,4})$"

Upvotes: 1

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