VB.NET email validation with Regex - regex

Question

I've tried implementing a rather simple email validation function that seems return a false match even though the input is a valid email. I have searched for any issues with the existing regex but it seems to be correct.
Even though the match returns a false value the program is stepping to the next validation level (which it shouldn't).
Here is the email validation function.
Function EmailAddressChecker(ByVal emailAddress As String) As Boolean
Dim regExPattern As String = "^[A-Z0-9._%+-]+#[A-Z0-9.-]+\.[A-Z]{2,4}$"
Dim emailAddressMatch As Match = Regex.Match(emailAddress, regExPattern)
If emailAddressMatch.Success Then
Return True
Else
Return False
End If
End Function
And for the form validation that calls upon the email validation function.
If (String.IsNullOrEmpty(EmailTextBox.Text) OrElse EmailAddressChecker(EmailTextBox.ToString)) Then
MessageBox.Show("Please enter a valid email addresss")
Return False
End If
The call for all of this happens on an click event which triggers a cascading serious of If statements checking to see if all the fields are set.
Skipping a large chunk of code the click event asks if "AreFieldsSet <> True". Inside of the "AreFieldsSet" function contains all the validation for multiple inputs; one of which is the email validation if statement.

Answer 1

Are the emails in UpperCase? If they aren't, they won't match.
If you want to modify the Regex so that it is Case insensitive, use this:
"^[a-zA-Z0-9._%+-]+#[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$"

Answer 2

To validate the email address you need to use the IsMatch function of the Regex object, it evaluate if the entry email address is valid.
Function EmailAddressChecker(ByVal emailAddress As String) As Boolean
Dim r As System.Text.RegularExpressions.Regex = Nothing
Dim regExPattern As String = "^[A-Z0-9._%+-]+#[A-Z0-9.-]+\.[A-Z]{2,4}$"
If r.IsMatch(emailAddress ,regExPattern ) Then
Return True
Else
Return False
End If
End Function

Answer 3

You can try this code for your form validation If (String.IsNullOrEmpty(EmailTextBox.Text) OrElse EmailAddressChecker(EmailTextBox.ToString)<>true) Then
MessageBox.Show("Please enter a valid email addresss")
Return False
End If

Answer 4

Public Shared Function ValidEmailAddress(ByVal emailAddress As String, ByRef errorMessage As String) As Boolean
If emailAddress.IndexOf("#") > -1 Then
If (emailAddress.IndexOf(".", emailAddress.IndexOf("#")) > emailAddress.IndexOf("#")) AndAlso emailAddress.Split(".").Length > 0 AndAlso emailAddress.Split(".")(1) <> "" Then
errorMessage = ""
Return True
End If
End If
Return False
End Function