---
title: "How to: Get and Set the Main Application Window"
description: Follow this example to get and set the main application window within Windows Presentation Foundation (WPF) application.
ms.date: "03/30/2017"
dev_langs: 
  - "csharp"
  - "vb"
helpviewer_keywords: 
  - "windows objects [WPF], setting"
  - "setting windows objects [WPF]"
  - "windows objects [WPF], getting"
  - "getting windows objects [WPF]"
ms.assetid: ec902bc4-4a59-46f5-8ec1-963b46789356
---
# How to: Get and Set the Main Application Window
This example shows how to get and set the main application window.  
  
## Example  
 The first <xref:System.Windows.Window> that is instantiated within a Windows Presentation Foundation (WPF) application is automatically set by <xref:System.Windows.Application> as the main application window. The first <xref:System.Windows.Window> to be instantiated will most likely be the window that is specified as the startup uniform resource identifier (URI) (see <xref:System.Windows.Application.StartupUri%2A>).  
  
 The first <xref:System.Windows.Window> could also be instantiated using code. One example is opening a window during application startup, like the following:  
  
 [!code-csharp[HOWTOWindowManagementSnippets#FirstWindowUsingCodeCODEBEHIND](~/samples/snippets/csharp/VS_Snippets_Wpf/HOWTOWindowManagementSnippets/CSharp/App.xaml.cs#firstwindowusingcodecodebehind)]
 [!code-vb[HOWTOWindowManagementSnippets#FirstWindowUsingCodeCODEBEHIND](~/samples/snippets/visualbasic/VS_Snippets_Wpf/HOWTOWindowManagementSnippets/visualbasic/application.xaml.vb#firstwindowusingcodecodebehind)]  
  
 Sometimes, the first instantiated <xref:System.Windows.Window> is not actually the main application window e.g. a splash screen. In this case, you can specify the main application window using markup, like the following:  
  
 [!code-xaml[ApplicationMainWindowSnippets#SetApplicationMainWindowXAML](~/samples/snippets/xaml/VS_Snippets_Wpf/ApplicationMainWindowSnippets/XAML/App.xaml#setapplicationmainwindowxaml)]  
  
 Whether the main window is specified automatically or manually, you can get the main window from <xref:System.Windows.Application.MainWindow%2A> using the following code, like the following:  
  
 [!code-csharp[ApplicationMainWindowSnippets#GetApplicationMainWindowCODE](~/samples/snippets/csharp/VS_Snippets_Wpf/ApplicationMainWindowSnippets/CSharp/App.xaml.cs#getapplicationmainwindowcode)]
 [!code-vb[ApplicationMainWindowSnippets#GetApplicationMainWindowCODE](~/samples/snippets/visualbasic/VS_Snippets_Wpf/ApplicationMainWindowSnippets/visualbasic/application.xaml.vb#getapplicationmainwindowcode)]