Form Control Validation for User Input in (VB.NET 2005)

Question

I am writing an application for my Notary business. I am a Notary Public in Iowa.

I have many types of control on the form. ComboBox (that can be modified), TextBox and MaskedTextBox. I know I can use the TextBoxBase class to cover the TextBox and also the MaskedTextBox, but my validation code is not doing anything. Nothing happens.

I have an ErrorProvider on the form called ErrorProvider. It has the "AutoValidate" option set to "EnableAllowFocusChange". The BlinkStyle is set to AlwaysBlink. All other properties are default.

I have three buttons on the form, too. Reset, Save and Close. Both the Reset and Close buttons are set to CausesValidation = False and the Save button is set to CausesValidation = True.

I need to make sure the "required" fields have a value when the Save button is clicked.

So, I figured I would use the Validated and Validating events of the controls. But, when clicking Save, nothing happens. The ErrorProvider doesnt even show. If I leave the control empty, still nothing happens.

This is my code:

    Private Sub Company_Validated(ByVal sender As Object, ByVal e As System.EventArgs) _
Handles Company.Validated, CompanyAddress.Validated, CompanyCity.Validated, CompanyZipCode.Validated, CompanyPhone.Validated, CompanyAddressRemit.Validated, CompanyCityRemit.Validated, CompanyZipCodeRemit.Validated
    ErrorProvider.SetError(CType(sender, TextBoxBase), String.Empty)
End Sub

Private Sub Company_Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) _
Handles Company.Validating, CompanyAddress.Validating, CompanyCity.Validating, CompanyZipCode.Validating, CompanyPhone.Validating, CompanyAddressRemit.Validating, CompanyCityRemit.Validating, CompanyZipCodeRemit.Validating
    Dim ErrorMessage As String = String.Empty
    Dim TheField As TextBoxBase = CType(sender, TextBoxBase)

    If TypeOf TheField Is MaskedTextBox Then
        CType(TheField, MaskedTextBox).TextMaskFormat = MaskFormat.ExcludePromptAndLiterals
    End If

    If Not IsValid(TheField, ErrorMessage) Then
        e.Cancel = True
        TheField.Select(0, TheField.Text.Length)
        ErrorProvider.SetError(TheField, ErrorMessage)
    End If
End Sub

Private Function IsValid(ByVal ControlName As TextBoxBase, ByVal ErrorMessage As String) As Boolean
    If String.IsNullOrEmpty(ControlName.Text.ToString) Then
        ErrorMessage = "This is a required field."
        Return False
    Else
        ErrorMessage = String.Empty
        Return True
    End If
End Function

Any ideas on what I am doing wrong?

Bjørn-Roger Kringsjå Bjørn-Roger Kringsjå · Accepted Answer · 2014-09-06T18:29:35

The String class in vb.net is a bit "odd". It's a reference type that acts (not all cases) like a value type. You need to change ByVal to ByRef.

Private Function IsValid(ByVal ControlName As TextBoxBase, ByRef ErrorMessage As String) As Boolean

Form Control Validation for User Input in (VB.NET 2005)

1 Answers