How to programmatically set UserControl to Topmost? - wpf

Question

How to programmatically set UserControl to Topmost of pc screen. I have multiple usercontrol in my wpf application, when I resize any usercontrol, I want to show this usercontrol top of the screen.

Answer 1

i want to show this usercontrol top of the screen.
If by that you mean "top of the screen" inside your application, then that is achieved by using Panel's ZIndex attached property.
Xaml :
<Grid x:Name="LayoutRoot">
<UserControl x:Name="TopMostUserControl"
Margin="10,140,106,48"
Panel.ZIndex="1"
Background="Green" />
<UserControl x:Name="SecondUserControl"
Margin="39,50,37,87"
Panel.ZIndex="0"
Background="red" />
</Grid>
C# :
public MainWindow()
{
InitializeComponent();
Panel.SetZIndex(TopMostUserControl, 1);
Panel.SetZIndex(SecondUserControl, 0);
}
<Grid x:Name="LayoutRoot">
<UserControl x:Name="TopMostUserControl"
Margin="10,140,106,48"
Background="Green" />
<UserControl x:Name="SecondUserControl"
Margin="39,50,37,87"
Background="red" />
</Grid>
Result :
However, if you mean to topmost that UserControl on the entire screen, then that would be something different, you should create another Window that hosts your topmost UserControl and you should change its TopMost property to true when you resize your other UserControls.
MainWindow :
<Grid x:Name="LayoutRoot">
<UserControl x:Name="FirstUserControl"
Margin="10,140,106,48"
Background="Green"
MouseDown="FirstUserControl_OnMouseDown" />
<UserControl x:Name="SecondUserControl"
Margin="39,50,37,87"
Background="red" />
</Grid>
Code Behind :
public partial class MainWindow : Window
{
public TopMostWindow TopMostWindow;
public MainWindow()
{
InitializeComponent();
TopMostWindow = new TopMostWindow();
TopMostWindow.Show();
}
private void FirstUserControl_OnSizeChanged(object sender, SizeChangedEventArgs e)
{
TopMostWindow.Topmost = true;
}
private void MainWindow_OnContentRendered(object sender, EventArgs e)
{
FirstUserControl.SizeChanged += FirstUserControl_OnSizeChanged;
SecondUserControl.SizeChanged += FirstUserControl_OnSizeChanged;
}
//This is to simulate the resizing
private void FirstUserControl_OnMouseDown(object sender, MouseButtonEventArgs e)
{
FirstUserControl.Width = 400;
}
}
TopMostWindow :
<Window x:Class="MvvmLight1.TopMostWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="TopMostWindow"
Width="300"
Height="300"
Topmost="False"
WindowStyle="None">
<Grid>
<UserControl x:Name="TopMostUserControl" Background="Blue" />
</Grid>
</Window>

Answer 2

It depends in which container you are using it. Or in what scenario. Basically in Grid you just need to specify it as a last element under Grid container. Otherwise use Panel.ZIndex="1" on the UserControl declaration in XAML