How to detect the first show of a WPF Window?

Question

I was wondering which is the correct way to detect when a WPF windows has been shown for the first time?

Solution 1

There is an event called Loaded that you can use to determine when your window is ready.

From MSDN

Occurs when the element is laid out, rendered, and ready for interaction.

set the handler in XAML

<StackPanel
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="SDKSample.FELoaded"
Loaded="OnLoad"
Name="root">
</StackPanel>

add the code-behind

void OnLoad(object sender, RoutedEventArgs e)
{
    Button b1 = new Button();
    b1.Content = "New Button";
    root.Children.Add(b1);
    b1.Height = 25;
    b1.Width = 200;
    b1.HorizontalAlignment = HorizontalAlignment.Left;
}

Solution 2

Loaded can be called more than once.

The Loaded event and the Initialized event

According to my test and the link above, Loaded event can be fired more than once.
So, you need to set a flag in the OnLoaded handler.

For example, if Stack Panel is inside TabItem control, loaded will be called every time you step into tab.

Comments

[Brandon Dybala]

According to this MSDN blog, the Loaded event actually occurs just before the first render.

[Jesse Chisholm]

And the OP wanted the WPF equivalent of Form.Shown, not the equivalent of Form.Loaded. WPF does not make this a trivial translation. This thread (stackoverflow.com/questions/9191256/window-shown-event-in-w‌​pf) suggests overriding OnContentRendered with your own flag for tracking whether it is the first time or not.

[Jesse Chisholm]

This will never get to the else clause as OnLoad is only ever called once. Before the first time the window is Shown. The OP's problem is that WPF does not have a Window.OnShown trivial equivalent.

[Bugs]

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