Window.Show Method

Reference

Definition

Namespace:: System.Windows

Assembly:: PresentationFramework.dll

Important

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Opens a window and returns without waiting for the newly opened window to close.

public:
 void Show();

public void Show ();

member this.Show : unit -> unit

Public Sub Show ()

Exceptions

InvalidOperationException

Show() is called on a window that is closing (Closing) or has been closed (Closed).

Examples

The following sample demonstrates how to open a modeless window.

// Initialize window
Window window = new Window();

// Show window modelessly
// NOTE: Returns without waiting for window to close
window.Show();

' Initialize window
Dim window As New Window()

' Show window modelessly
' NOTE: Returns without waiting for window to close
window.Show()

Remarks

When the Window class is instantiated, it is not visible by default. Show shows a window and returns immediately, without waiting for the window to be closed. Consequently, the opened window does not prevent users from interacting with other windows in the application. This type of window is called a modeless window. Common examples of modeless windows are properties windows, toolboxes, and palettes. To restrict a user to interacting with a specific window, the window must be opened by calling ShowDialog.

A window that is opened by calling Show does not automatically have a relationship with the window that opened it; specifically, the opened window does not know which window opened it. This relationship can be established using the Owner property and managed using the OwnedWindows property.

Calling Show achieves the same end result as setting Visibility property of the Window object to Visible. However, there is a difference between the two from a timing perspective.

Calling Show is a synchronous operation that returns only after the Loaded event on the child window has been raised:

Window w = new Window();
w.Loaded += delegate { System.Console.WriteLine("This is written first."); };
w.Show();
System.Console.WriteLine("This is written last.");

Dim w As New Window()
AddHandler w.Loaded, Sub() System.Console.WriteLine("This is written first.")
w.Show()
System.Console.WriteLine("This is written last.")

Setting Visibility, however, is an asynchronous operation that returns immediately:

Window w2 = new Window();
w2.Loaded += delegate { System.Console.WriteLine("This is written last."); };
w2.Visibility = Visibility.Visible;
System.Console.WriteLine("This is written first.");

Dim w2 As New Window()
AddHandler w2.Loaded, Sub() System.Console.WriteLine("This is written last.")
w2.Visibility = Visibility.Visible
System.Console.WriteLine("This is written first.")

When setting Visibility, any window events you register before you set Visibility may not be raised until after the method in which you set Visibility has completed execution.

Applies to

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