managing-wpf-application-lifecycle

# WPF Application Lifecycle Patterns

Managing application startup, shutdown, and runtime behavior.

**Advanced Patterns:** See [ADVANCED.md](ADVANCED.md) for single instance, settings, and activation handling.

## 1. Application Lifecycle Overview

```
Application Start
    │
    ├─ App Constructor
    ├─ App.OnStartup() / Startup event
    ├─ MainWindow Constructor
    ├─ MainWindow.Loaded event
    │
    ▼
Running State
    │
    ├─ Activated / Deactivated events
    ├─ SessionEnding event (logoff/shutdown)
    │
    ▼
Shutdown Initiated
    │
    ├─ Window.Closing event (can cancel)
    ├─ Window.Closed event
    ├─ App.OnExit() / Exit event
    │
    ▼
Application End
```

---

## 2. Startup Handling

### 2.1 App.xaml Startup

```xml
<Application x:Class="MyApp.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml"
             Startup="Application_Startup"
             Exit="Application_Exit"
             SessionEnding="Application_SessionEnding">
    <Application.Resources>
        <!-- Resources -->
    </Application.Resources>
</Application>
```

### 2.2 Override OnStartup

```csharp
namespace MyApp;

using System.Windows;

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        // Process command line arguments
        ProcessCommandLineArgs(e.Args);

        // Initialize services
        InitializeServices();

        // Create and show main window manually (if StartupUri not set)
        var mainWindow = new MainWindow();
        mainWindow.Show();
    }

    private void ProcessCommandLineArgs(string[] args)
    {
        foreach (var arg in args)
        {
            if (arg.Equals("--debug", StringComparison.OrdinalIgnoreCase))
            {
                // Enable debug mode
            }
            else if (arg.StartsWith("-