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.
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();
}
}
I have a WPF application without an application.xaml, since I need to do the Main() method by myself. Therefore I neither have an ApplicationDefinition nor an application resource. I currently attach the resource dictionary to the application at the application startup
Of course the WPF Designer complains now about missing resources.
So I want to get rid of two problems:
- I don't want to attach the resource dictionary manually at startup
- I want to get the resources also work at design time in the WPF designer
Is there any help for this problem?
Thanks
Martin
There is a possibility to use the Main() method for yourself
Just delete the following property from the xamlcode of Application.xaml:
StartupUri="MainWindow.xaml"
Then add the following in the code-behind of the Application.xaml:
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
// My code goes here, but nothing ever happens.
base.OnStartup(e);
}
}
Now you can still use the Application.xaml for your resources and also have your specific startup procedure.
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'm accustomed to Winforms where you can create a window and display it via:
Window.ShowDialogue();
I'm using the default MainWindow.xaml in a class library project. I had to delete the App.xaml file to complete the conversion. I want to launch the main window in a simple test. E.G.
[TestMethod]
public void RunPd()
{
MainWindow window = new MainWindow();
window.ShowDialogue();
}
Show/ShowDialogue() is not available. All I have is
GetChildren<>, GetParents<>, InitializeComponent and LoadTree<>.
How can I display MainWindow.xaml?
UPDATE
Main window code:
public partial class MainWindow : Window
Try ShowDialog()
public void RunPd()
{
MainWindow window = new MainWindow();
window.ShowDialog();
}
I'm not sure if this could be the issue or not (your question is a bit vague); however, right-click on the xaml file in the VisualStudio project and click on Properties. Then make sure that "Build Action" is set to "Page."
If this is already set, please make a comment as to that as well.
I had to add a reference to WindowsBase.dll, System.Xaml, PrentationationCore and PrentationFramework. Once I added these references the unit test worked.
Curious as to why I did not need to add these assemblies in Winforms...?
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.