Window.TopMost Property
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Gets or sets a value that indicates whether the application window is always displayed in front of other windows.
Namespace: System.Windows
Assembly: System.Windows (in System.Windows.dll)
Syntax
'Declaration
Public Property TopMost As Boolean
public bool TopMost { get; set; }
Property Value
Type: System.Boolean
true if the application window is topmost; otherwise, false. The default is false.
Exceptions
| Exception | Condition |
|---|---|
| NotSupportedException | The application is not running outside the browser. |
| UnauthorizedAccessException | The current thread is not the user interface (UI) thread. |
| SecurityException | When setting this property, except in response to a user-initiated action, the Application.Startup event has already occurred and Application.HasElevatedPermissions is false. |
Remarks
You can set this property only in the following cases:
In response to a user-initiated action, for example, in a button Click event handler.
Before the Application.Startup event has completed (that is, in an IApplicationService.StartService method, an IApplicationLifetimeAware.Starting method, or a Startup event handler).
In a trusted application.
If multiple applications have main windows with TopMost values of true, the actual topmost window is the one most recently active.
In Silverlight 5, trusted, out-of-browser applications can create multiple Window instances and manipulate them programmatically. However, the TopMost property is meaningful only for the Application.MainWindow instance.
Version Information
Silverlight
Supported in: 5, 4
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
See Also