#1,066 – Elements Must Be Visible and Enabled to Fire Events

Events fired from user interface elements in WPF are typically routed events, firing events from elements up or down the logical tree after the source element has fired the event.

A user interface element must be both visible (Visibility = Visible) and enabled (IsEnabled = true) in order to fire an event.  If an element is not visible or is disabled, the topmost element beneath the element may fire the event instead.

Below, if we set IsEnabled on the Label to false, its MouseDown event will not fire and the StackPanel will become the source of the event instead.

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Events" Width="208" Height="183"
        MouseDown="Window_MouseDown">

    <StackPanel MouseDown="StackPanel_MouseDown"
                Background="AliceBlue" Margin="10">
        <Label Content="Label" Background="Orange" Margin="10"
               MouseDown="Label_MouseDown"
               IsEnabled="False"/>
    </StackPanel>
</Window>

When we click on the Label, the StackPanel fires the MouseDown event, followed by the parent Window.