I'm trying to run a window, close it, and then run a second window, in a similar way that seems to work with Windows Forms.
namespace WpfApplication1
{
public partial class App : Application
{
[STAThread]
public static void Main()
{
Application app = new Application();
//windowMain.Show();
app.ShutdownMode = ShutdownMode.OnExplicitShutdown;
MainWindow windowMain = new MainWindow();
app.Run(windowMain);
Window1 window1 = new Window1();
window1.Show();
app.Run(window1);
}
}
}
I've set the Build Action in the App.xaml properties from ApplicationDefinition to Page, but the programme throws an exception when window1 is initialised. What am I doing wrong?
Edit: I've modified the xaml in App.xaml as suggested by first answer and edited main as suggested by the comment.
<Application x:Class="WpfApplication1.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml"
ShutdownMode="OnExplicitShutdown">
<Application.Resources>
</Application.Resources>
</Application>
but I'm still getting the exception.
OK this is what I've divined so far. The Solution Builder looks for a Main() function. Why its not a WinMain() function I'm still not a hundred per cent clear on. If there is no Main(), you get an error. You can have more than one Main() as long as the Project properties: "Application" page/tab: property: "StartUp Object" is set to point to one of the main()s. This is done from an automatically created drop down list.
When a “WPF Application” project is created, Visual Studio(VS) create an xaml file called “App.xaml”. This is a class declaration where “App” is derived from the “Application” Class. VS also automatically generates hidden files for an xaml file. It creates a “name.g.i.cs” file, when the xaml file is created. It creates a “name.g.cs” file the first time the project is built after the creation of the xaml file. In this case it creates “App.g.cs” and “App.g.i.cs”. These files are hidden by default. To view them, press the “Show all files” button at the top of the Solution Explorer, they can be found in “\ obj\86\Debug” folder. When you delete an xaml file the “name.g.i.cs” and the “name.g.cs” files remain and are not deleted.
The “App.xaml” file’s “build Action” property is set to “Application Definition” when created by VS. When this property is set to “Application Definition” a Main() function is automatically created in “name.g.i.cs”:
[System.STAThreadAttribute()]
[System.Diagnostics.DebuggerNonUserCodeAttribute()]
public static void Main()
{
WpfApplication8.App app = new WpfApplication8.App();
app.InitializeComponent();
app.Run();
}
When this property is set to “Page”, the Main() function is automatically removed by VS. You can create new “Application” derived classes in code or in xaml. I haven’t found a neat way to do it in xaml. There doesn’t seem to be a template for an xaml “Application” derived class. I created a “.cs” code file and then renamed it to an .xaml file. For some reason VS won’t allow you to have more than one xaml “Application” declaration file set to “Application Build”, it doesn’t even give you the option of choosing one in the "Project: Properties: Application": “Startup Object” property.
As you can see in the hidden Main(), an instance of “App” is instantiated and run. If using your own Main() function: an instance of, the base “Application” class, or an “Application” derived class (whether declared in code or in xaml), can be declared and run. The “Application” class should only be instantiated once and should only be run once. If the “Application” derived class is declared in xaml then a simple application can be run by using the StartUpUri property in the xaml file: StartupUri="Windowname.xaml". Alternatively the top level UI programme logic can be placed in a Startup event handler. If “Startup="Application_Startup" is placed in the “App.xaml” file then an event handler can be written:
private void Application_Startup(object sender, StartupEventArgs e)
{
MainWindow windowMain = new MainWindow();
windowMain.ShowDialog();
Window1 window1 = new Window1();
window1.ShowDialog();
Shutdown();
}
You have to use ShowDialog() here, because it blocks until the window is closed. If you used Show() instead, it would show one window, then immediately show the other one and shutdown the application. In this case there's no need to call the Run() method yourself, that's done automatically.
The “Application” class instance can be run in code whether its declared in code or in xaml. You can then perform initialisation code prior to calling Run(). This would be placed in the Application_ Startup() event handler using the other way. However, if the “Application.Run” call is ever made in the programme, then no windows should be opened (using show() or ShowDialog()) in Main() or anywhere outside of the Application Class or within events and functions called from those events, called during “Application.Run()”.
The Application class has a ShutdownMode property (Application.ShutdownMode). The default for this is: “OnMainWindowClose”. This property can also be set to “OnLastWindowClose” or “OnExplicitShutdown” in code or in the xaml. You will need to reset this if you don't want the programme to close down when the MainWindow is closed.
I think for my purposes it is better not to use the Application class at all and just call the windows using Show() and “ShowDialog()”. This way I can use WPF pages but I could also call Windows Forms, or DirectX screens, as long as they are not open at the same time, or have no UI at all, if the programme is running remotely. Is there any reason for not doing it this way?
I think your application is shuting down when you close the first window. You need to set Application.ShutdownMode to OnExplicitShutdown.
If all you want to do is to show one window, when that closes, show another and when that closes, shutdown the whole application, you should keep the Build action as ApplicationDefinition, set ShutdownMode to OnExplicitShutdown (probably in App.xaml, but you can it in code-behind too) and put the following code in an event handler of the Startup event of your application:
private void Application_Startup(object sender, StartupEventArgs e)
{
MainWindow windowMain = new MainWindow();
windowMain.ShowDialog();
Window1 window1 = new Window1();
window1.ShowDialog();
Shutdown();
}
You have to use ShowDialog() here, because it blocks until the window is closed. If you used Show() instead, it would show one window, then immediatelly show the other one and shutdown the application.
There's no need to run the Run() method yourself, that's done automatically.
Related
I am trying to learn WPF. I have done mostly back-end programming, except I did some C++ UI programming in the nineties. So far, I have created a simple maintenance application with a few screens and I can run it fine. I can navigate around, insert records and whatnot. However, I have to set my app.xaml startup location to MainWindow.xaml and then instantiate my actual window inside the C# code of the class linked to it. If I delete the MainWindow.xaml file and set my StartupLocation to wndMyMainWindow.cs, I get an error saying that it can not find the file. Is there any way around this? It seems sort of weird to require a non C# file type in what is supposed to be a C# UI framework.
In your App.xaml remove the StartupUri="MainWindow.xaml". Then add Startup="App_OnStartup" and create the matching method in your App.xaml.cs file like:
public partial class App : Application
{
private void App_OnStartup(object sender, StartupEventArgs e)
{
// do some code stuff like initializing your ViewModel or something else
// Instanciate the view you want to display and show it
MainWindow mainWindow = new MainWindow();
mainWindow.ShowDialog();
}
}
My WPF application calls upon a separate project to handle a login process BEFORE the Main Window in my application is shown. This creates a problem and causes "Application Shutdown" errors because the FIRST window in the application has closed. How can I handle the login process BEFORE my Main Window is shown? Every search I find comes up with references to Prism or MEF... which I cannot use.
If you want to control everything from the very start of your application, you need to create your own main method and use this as "start object" (see project properties). More details can be found in another SO answer, but this is its essence:
[STAThread]
public static void Main(string[] args)
{
// Do anything you like before running the main window.
// ...
// Proceed with usual application flow.
var app = new MyApplication();
var win = new MyWindow();
app.Run(win);
}
To prevent the application shutdown error, you can change Application.ShutdownMode to OnExplicitShutdown. And explicitly call Application.Shutdown Method to close your application when needed.
Have you tried adding code to the App.xaml.cs file? There are places you can place code in there that runs before the main window is opened. In addition to a constructor, there's the Startup event that you can assign a handler to in the App.xaml file:
<Application x:Class="CarSystem.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DispatcherUnhandledException="App_DispatcherUnhandledException"
Exit="Application_Exit"
Startup="Application_Startup"
StartupUri="MainWindow.xaml">
And, of course there's the Main method in the same file that you could throw code into, as well.
I have a WPF window in a project with a XAML file and associated C# code behind file. If I set "StartupUri=MainWindow.xaml" in App.xaml to this window the window opens as expected when I start my application.
However, I want my application to to take command line parameters and then decided if it should open the GUI or not. So instead I've set "Startup=Application_Startup" in my App.xaml file which is defined as shown below.
private void Application_Startup(object sender, StartupEventArgs e)
{
if (e.Args.Length > 1)
{
//do automated tasks
}
else
{
//open ui
MainWindow window = new MainWindow();
this.MainWindow = window;
window.Show();
}
}
Yet when I run this the window displayed is totally blank.
Adding window.InitializeComponent() seems to do the trick:
MainWindow window = new MainWindow();
Application.Current.MainWindow = window;
window.InitializeComponent();
window.Show();
I usually like to have a little explanation on why something does or doesn't work. I have no clue in this case. I can see that the examples online don't include InitializeComponent, and yet I produce the same exact error as you do (event without checking for args).
I created a sample application, and removed the StartupUri and set the Startup to the method you provided. Everything seems to work as expected, the content of the window is displayed, so maybe, as Daniel mentioned, you're missing the call to InitializeComponent method in your MainWindow constructor.
I am new to WPF. In winforms I used to create a presenter and new it up in the static main(). The presenter's constructor would be given a reference to to the main form before the form would be shown.
MainPresenter presenter = new MainPresenter(myform);
Application.Start(myform);
How can I do this in WPF? I noticed that App.xaml has a 'StartUri' property that specifies which form to load. Where is the main entry point to a WPF application and how do I change the default behavior here?
Thanks!
You could do this in the constructor or Loaded event of either the main form (specified in startUri) or in the App.xaml.cs file
This post demonstrates what I needed perfectly.
http://www.developingfor.net/wpf/accessing-command-line-arguments-in-wpf.html
Startup="Application_Startup"
This was added in the App.xaml Application declaration.
I then wired the event in the App.xaml.cs
private void Application_Startup(object sender, StartupEventArgs e)
{
}
This helped a lot too:
http://social.msdn.microsoft.com/forums/en-US/wpf/thread/e5757d5c-28f3-4233-8a5f-00116587d5c7
I'm having problems understanding how WPF app.xaml works. Is it like Main method in winforms programing?
What I want is a MainController class which keeps track of my Window object. For example:
public MainController()
{
_windowMain = new WindowMain(this);
}
public WindowMain GetWindowMain
{
get { _windowMain; }
}
And so on with all the windows I have in my project. But where should my MainController be initialized?
Check the StartupUri property of the App.xaml file. It links in a Window's XAML file within your project to be launched at startup.
If you want to avoid this, then I believe you can override a method in App.xaml.cs to launch the window explicitly via your controller.
You should understand that the compiler makes a class called 'App' that overrides System.Windows.Application by compiling your App.xaml and App.xaml.cs files. Check the documentation for that class to learn more about the lifecycle management of your WPF application.