Question

I have a ‘Login’ button that I want to be disabled until 3 text boxes on the same WPF form are populated with text (user, password, server).

I have a backing object with a boolean property called IsLoginEnabled which returns True if and only if all 3 controls have data. However, when should I be checking this property? Should it be on the LostFocus event of each of the 3 dependent controls?

Thanks!

vg1890

Answer 1

I’d get the ‘backing object’ to raise the IsLoginEnabled changed event when any of the 3 fields are updated. You can then bind the button to the IsLoginEnabled property and not have to keep checking it.

The pseudocode would look something like this:

Public Event IsLoginEnabledChanged As EventHandler  Public Property User() As String Get..   ' snipped for brevity Set(ByVal value As String)    mUser = value    RaiseEvent IsLoginEnabledChanged(Me, New EventArgs()) End Set  ' do the same in the Set for Password() and Server() properties 

The trick to this is naming the Event [PropertyName]Changed (i.e. IsLogonEnabledChanged) – because raising this event will automagically notify any bound controls :o)