Regex Match to validate more than one textbox?

Question

If Not Regex.Match(txt_Username.Text, "^[a-zA-Z0-9]*$", RegexOptions.IgnoreCase).Success Then

How can I change this line so it checks txt_Password as well as txt_Username?

Thanks

Answer 1

You can share a regex by making a regex object first, and then using its instance methods, like this:

Dim checker As Regex = New Regex("^[a-zA-Z0-9]*$", RegexOptions.IgnoreCase)
If Not checker.Match(txt_Username.Text).Success OrElse Not checker.Match(txt_Password.Text).Success

Answer 2

Another approach is to create an array of the values you want to test, then use Array.TrueForAll(). This example also makes sure that none of them are blank:

    Dim values() As String = {txt_Username.Text, txt_Password.Text}
    If Not Array.TrueForAll(values, Function(x) Regex.IsMatch(x, "^[a-zA-Z0-9]*$", RegexOptions.IgnoreCase)) _
        OrElse Not Array.TrueForAll(values, Function(x) x.Trim.Length > 0) Then

        MessageBox.Show("Invalid UserName and/or Password")

    End If

Slightly overkill for just two TextBoxes, but just something to keep in your toolbox for when you need to check a series of TextBoxes.

Answer 3

Regex can be applied by using its static methods but also by creating a reusable Regex instance:

Dim validator As New Regex("^[a-zA-Z0-9]*$", RegexOptions.IgnoreCase)
If Not validator.IsMatch(txt_Username.Text) OrElse _
   Not validator.IsMatch(txt_Password.Text) Then
   ...
End If