WPF 中没有 Main() 吗？

Question

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?

Answer 1

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();
}

Answer 2

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.gics 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();
        }
    }
}

Answer 3

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.

Answer 4

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

Answer 5

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.

Answer 6

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.

Answer 7

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>