CODEWITHSUNDEEP
c#wpfc#-4.0program-entry-point
Juice
Juice

Reputation: 2870

No Main() in WPF?

I am a beginner when it comes to programming but I was sure that one of the universal rules was that a program starts with Main(). I do not see one when I create a WPF project. Is Main() simply named something differently in WPF?

Upvotes: 147

Views: 99424

Answers (8)

Anandu G Nath
Anandu G Nath

Reputation: 1

To clear this is error, do the following steps:

  • Right-click on App.Xaml
  • Properties > Change Build Action
  • From Page to > ApplicationDefinition
  • Build the solution and run

It will work fine - refer to this screenshot:

enter image description here

Upvotes: 0

Andreas Kahler
Andreas Kahler

Reputation: 2353

The Main() method is created automatically. If you want to provide your own you have to (tested in VS2013, VS2017 and VS2019):

  • Right-click App.xaml in the solution explorer, select Properties
  • Change 'Build Action' to 'Page' (initial value is 'ApplicationDefinition')

Then just add a Main() method to App.xaml.cs. It could be like this:

[STAThread]
public static void Main()
{
    var application = new App();
    application.InitializeComponent();
    application.Run();
}

Upvotes: 156

user10372515
user10372515

Reputation: 31

In case you removed default App.xaml and MinWindow.xaml, better to edit .csproj After adding App.xaml manually, your .csproj will be:

<Page Include ="App.xaml">
       <DependentUpon>MSBuild:Compile</DependentUpon>
       <SubType>Code</SubType>
</Page>

Change this to:

<ApplicationDefinition Include="App.xaml">
    <Generator>MSBuild:Compile</Generator>
    <SubType>Designer</SubType>
</ApplicationDefinition>

Upvotes: 3

Declan Taylor
Declan Taylor

Reputation: 405

I copied files that wouldn't load in another project that was without a mainwindow into a new one and got this error.

For me it took doing the opposite approach to Andreas Kahler to fix:

After making a window file and setting the startup uri to this file i switched Page to ApplicationDefinition of App.xaml 'Build Action' property.

Upvotes: 1

Franci Penov
Franci Penov

Reputation: 75982

Main() is automatically provided by the CLR and the WPF.

The C# compiler takes a command-line switch /m which specifies the type that contains the implementation of Main(). By convention, if no startup object is explicitly specified, the CLR will lookup any class that has a static Main() method and will call it. (As @Marc Gravel pointed out in his comment)

In the case of WPF, the Main() is automatically generated when App.xaml is built and the /m switch is specified to make the C# compiler use that class as entry point. If you look at the project properties however, you'll find there's a setting for you to choose the startup object. So if you want, you can provide your own class that implements Main().

Note that this will put the responsibility on you to create the Application instance and call its Run() method to ensure that the WPF infrastructure is started properly.

Upvotes: 17

Annath
Annath

Reputation: 1262

main() is a standard entry point for an application, but all applications are structured that way. In a XAML project, the App.XAML file specifies the entry point where it says StartupUri="MainWindow.xaml".

As it is stated by others, the actual main function is generated based on the contents of the XAML files in the project.

Upvotes: 6

Marc Gravell
Marc Gravell

Reputation: 1062502

It is generated during build, but you can provide your own (disambiguating it in project-properties as necessary). Look in obj/debug for an app file; I have (courtesy of "C# 2010 Express") App.g.i.cs with:

namespace WpfApplication1 {


    /// <summary>
    /// App
    /// </summary>
    [System.CodeDom.Compiler.GeneratedCodeAttribute("PresentationBuildTasks", "4.0.0.0")]
    public partial class App : System.Windows.Application {

        /// <summary>
        /// InitializeComponent
        /// </summary>
        [System.Diagnostics.DebuggerNonUserCodeAttribute()]
        public void InitializeComponent() {

            #line 4 "..\..\..\App.xaml"
            this.StartupUri = new System.Uri("MainWindow.xaml", System.UriKind.Relative);

            #line default
            #line hidden
        }

        /// <summary>
        /// Application Entry Point.
        /// </summary>
        [System.STAThreadAttribute()]
        [System.Diagnostics.DebuggerNonUserCodeAttribute()]
        public static void Main() {
            WpfApplication1.App app = new WpfApplication1.App();
            app.InitializeComponent();
            app.Run();
        }
    }
}

Upvotes: 81

Vlad
Vlad

Reputation: 35584

Main() is generated during compilation. You can find it in App.g.cs (in obj/{Debug,Release} folder).

Upvotes: 10

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