I have a WPF .NET 4 application where I override the OnStartup method in order to process the file passed to my application. However, it seems that this method is not being called when the application runs. I put an exception in there and even a breakpoint and it starts up and completely ignores this.
Am I missing something?
Code for App.xml.cs:
/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
throw new NotImplementedException();
}
}
Contents of App.xaml:
<Application x:Class="XGN_Image_Downloader.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
</Application.Resources>
</Application>
EDIT: Found it! The x:Class attribute in App.xaml did not match the App.xaml.cs class :) That's what you get for coding while drinking wine. (Thanks to this thread: WPF app startup problems)
Found it, I had to set the x:Class attribute in App.xaml to the same class as the App.xaml.cs class. This was an error caused by bad refactoring on my side.
x:Class must be filled with the namespace and exact class name on App.xml.cs
Eg: <Application x:Class="Namespace.ClassName"
Related
I have a question for people familiar with the Community Toolkit MVVM regarding best practices for building up the Views part of MVVM. I have started a new project to try to get things figured out before trying to implement this into my actual project. My main question is, if you have multiple views/windows for different purposes in a WPF application, is it not a good idea to place them into a View or Views folder? If so, I'm having a hard time getting the application to launch the main window.
System.IO.IOException: 'Cannot locate resource 'wpf_mvvm_test.views.mainwindow.xaml'.'
The first thing I tried was just moving the MainWindow.xaml file to the views folder, which caused the runtime error as soon as it compiled. I started changing the namespace references for the MainWindow.xaml, MainWindow.xaml.cs, App.xaml, App.xaml.cs, as well as the startup URI to reflect the namespace for the folder, WPF_MVVM_Test.Views, and none of the changes I have made have prevented the error. I did leave the App.xaml file in the main project, not in the folder. If I try to move it into the Views folder, even if I change its x:Class and the App.xaml.cs namespace to WPF_MVVM_Test, when I try to run it, it gives me an error that there is no static Main entrypoint.
Is there no way to place the WPF window files into a folder? If it's not possible, it's not possible, but if it is possible, I would love to figure out how, as it would make it easier to keep the solution organized.
MainWindow.xaml:
<Window x:Class="WPF_MVVM_Test.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WPF_MVVM_Test.Views"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
</Grid>
</Window>
MainWindow.xaml.cs:
using System.Windows;
using WPF_MVVM_Test.ViewModels;
using WPF_MVVM_Test.Views;
namespace WPF_MVVM_Test.Views
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MainViewModel();
}
}
}
App.xaml:
<Application x:Class="WPF_MVVM_Test.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WPF_MVVM_Test"
StartupUri="WPF_MVVM_Test.Views.MainWindow.xaml">
<Application.Resources>
</Application.Resources>
</Application>
App.xaml.cs:
using System.Windows;
using WPF_MVVM_Test.Views;
namespace WPF_MVVM_Test
{
/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
}
}
Thanks to ASh for the very helpful reply. I'm not sure what is preventing the application from compiling by moving the MainWindow.xaml file in to a folder, but the workaround references ASh provided definitely works.
First, I removed the StartupUri statement from the App.xaml file.
Second, in the App.xaml.cs file, I added an override for an OnStartup event as shown below, ensuring the folder that the MainWindow files are located in is in the using statements.
App.xaml.cs
using System.Windows;
using WPF_MVVM_Test.Views;
namespace WPF_MVVM_Test
{
public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
new MainWindow().Show();
}
}
}
When I include an assembly containing a ResourceDictionary using the following pack syntax:
"pack://application:,,,/WpfCore;component/ResourceDictionaries/ThemedControls.xaml"
It works as expected, but as soon as I add a code behind file to the XAML of the ResourceDictionary, the following error is thrown:
“An error occurred while finding the resource dictionary”
The code behind is added to the XAML in the usual way:
< ResourceDictionary x:Class="com.mycompany.WpfCore.ResourceDictionaries.ThemedControls"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006">
</ResourceDictionary>
and looks like this:
namespace com.mycompany.WpfCore.ResourceDictionaries
{
public partial class ThemedControls : ResourceDictionary
{
public ThemedControls ()
{
InitializeComponent();
}
}
}
Intuition tells me this is a namespace problem, but all the variations I've tried fail. What am I doing wrong or is this a limitation of WPF ResourceDictionaries?
Edit:
Seems the question detail was called out and found to be wanting.
The initial example had the namespace simplified. The default namespace for the WpfCore project is com.mycompany.WpfCore which I have now added into the code examples above.
The ThemedControls.xaml and ThemedControls.xaml.cs files are located in a subfolder called ResourceDictionaries within the WpfCore project folder.
The resulting assembly is used as a referenced assembly in another solution and this is where the Pack URI is being used.
Edit 2:
After playing around with the build action for the xaml files (changing from page to resource and back again) things started working. Marking Sheridan's answer as correct.
I don't think that you have declared your ResourceDictionary quite correctly... the application name really should be in the namespace. This should work... at least it works for me:
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
x:Class="WpfCore.ResourceDictionaries.ThemedControls">
</ResourceDictionary>
Code behind:
namespace WpfCore.ResourceDictionaries
{
public partial class ThemedControls : ResourceDictionary
{
public ThemedControls()
{
InitializeComponent();
}
}
}
I wrote an application for Server-client connection.
In WPF project, there is an App.xaml that have start up method.
I want to do the same with an App2.xaml by copy and change the name + Startup URI for client UI
The code in App2.xaml like this
<Application x:Class="assembly_line_balance_demo_ga_dp_tttn09_2013.App2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" StartupUri="View/MainWindow.xaml">
<Application.Resources>
</Application.Resources>
</Application>
But after I rebuild my project, it does not show new start up object in Properties solution.
Because Client & Server share the code inside, so I need to config both UI in one project and build to 2 different apps.
Please help
I think that it is allowed just One App.xaml per Project.
You can change the Start-Up Uri
like this:
On the file App.xaml
Remove the StartupUri attribute:
<Application x:Class="WpfApplication4.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<!-- StartupUri="MainWindow.xaml" -->
<Application.Resources>
</Application.Resources>
</Application>
on the file App.xaml.cs
/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : Application
{
// Add this override function
protected override void OnStartup(StartupEventArgs e)
{
if(e.Args.Contains("Client"))
this.StartupUri = new Uri("View/MainWindow.xaml", UriKind.RelativeOrAbsolute);
else
this.StartupUri = new Uri("View/MainWindowServer.xaml", UriKind.RelativeOrAbsolute);
}
}
Then you can call
YourApplication.exe Client
or
YourApplication.exe Server
This might be an extremely dumb question, but I simply can't understand the problem at the moment.
I have an App.xaml file that defines application level resources :
<Application x:Class="WpfMPManager.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml">
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="MyDictionnary.xaml"/>
</ResourceDictionary>
</Application.Resources>
For various reasons, I start this application through a .cs file like that (there actually is a lot more going on in this file).
[STAThread]
static void Main(params string[] args)
{
App myApp = new App();
MainWindow myWindow = new MainWindow();
myApp.Run(myWindow);
}
However, when I start the application in this way, my application resource dictionnaries are empty (and they are indeed filled if I start the application through my App.xml).
Should I call a specific method on the Application object to force it to load the resource dictionaries defined in the .xaml file ?
Thanks in advance.
Answering my own question in case anyone stumbles on that
It seems it's enough to call myApp.InitializeComponent() which is not called by the default constructor. Could have figured it out faster.
Im new to Expression and by accident I deleted the App.xaml file. I think this is an important file and I cannot workout how to create an equivalent.
Please help,
Andy
Create a new project and copy that one.
<Application x:Class="Test.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="Window1.xaml">
<Application.Resources>
</Application.Resources>
</Application>
Unless you had Application Resources defined, then you may be in trouble.
Might be a good argument for Source Control.
You can create a new Page and call it App.xaml.
Replace its markup as benPearce indicated with this:
<Application x:Class="Test.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="Window1.xaml">
<Application.Resources>
</Application.Resources>
</Application>
Replace "Test" above with your namespace and "Window1" with the name of the first page you want shown in your project.
Replace the class in the App.xaml.cs code-behind with this:
public partial class App : Application
{
[STAThread]
public static void Main()
{
YourNamespace.App app = new YourNamespace.App();
app.InitializeComponent();
app.Run();
}
}
Ensure that your Project Properties are set in the "Application" area such that your startup object is YourNamespace.App.
Perform a build and you shouldn't get anymore errors related to 'App'.