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name: optimizing-wpf-memory description: Covers WPF memory optimization including Freezable patterns, common memory leak causes, and diagnostic techniques. Use when experiencing memory growth, implementing resource caching, or debugging memory issues.

WPF Memory Optimization

1. Freezable Pattern

Why Freeze?

Basic Usage

Copy// Always freeze static resources
var brush = new SolidColorBrush(Colors.Red);
brush.Freeze();

var pen = new Pen(Brushes.Black, 1);
pen.Freeze();

XAML Freeze

Copy<Window xmlns:po="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options"
        mc:Ignorable="po">
    <Window.Resources>
        <SolidColorBrush x:Key="FrozenBrush" Color="Red" po:Freeze="True"/>
    </Window.Resources>
</Window>

When Freeze Fails

Copyif (brush.CanFreeze)
    brush.Freeze();
else
    // Has bindings or animations - cannot freeze

Modifying Frozen Objects

Copyvar clone = frozenBrush.Clone(); // Creates unfrozen copy
clone.Color = Colors.Blue;
clone.Freeze(); // Freeze again if needed

2. Common Memory Leaks

Event Handler Leaks

Copy// ❌ LEAK: Static event holds reference
SomeStaticClass.StaticEvent += OnEvent;

// ✅ FIX: Unsubscribe in Unloaded
Unloaded += (s, e) => SomeStaticClass.StaticEvent -= OnEvent;

CompositionTarget.Rendering Leak

Copy// ❌ LEAK: Never unsubscribed
CompositionTarget.Rendering += OnRendering;

// ✅ FIX: Always unsubscribe
Loaded += (s, e) => CompositionTarget.Rendering += OnRendering;
Unloaded += (s, e) => CompositionTarget.Rendering -= OnRendering;

Binding Without INotifyPropertyChanged

Copy// ❌ LEAK: PropertyDescriptor retained
public string Name { get; set; } // No INPC

// ✅ FIX: Implement INPC
public string Name
{
    get => _name;
    set { _name = value; OnPropertyChanged(); }
}

DispatcherTimer Leak

Copy// ❌ LEAK: Timer keeps running
_timer = new DispatcherTimer();
_timer.Tick += OnTick;
_timer.Start();

// ✅ FIX: Stop and cleanup
Unloaded += (s, e) =>
{
    _timer.Stop();
    _timer.Tick -= OnTick;
};

Image Resource Leak

Copy// ❌ LEAK: Stream kept open
var bitmap = new BitmapImage(new Uri(path));

// ✅ FIX: Load immediately and release stream
var bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.CacheOption = BitmapCacheOption.OnLoad;
bitmap.UriSource = new Uri(path);
bitmap.EndInit();
bitmap.Freeze();

3. Diagnostic Checklist

Code Review Points

• All static event subscriptions have unsubscribe logic
• CompositionTarget.Rendering unsubscribed in Unloaded
• DispatcherTimer stopped in Unloaded
• ViewModels implement INotifyPropertyChanged
• Images use BitmapCacheOption.OnLoad
• Static resources are Frozen

Diagnostic Tools

Memory Monitor

Copypublic static class MemoryMonitor
{
    public static void LogMemory(string context)
    {
        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();

        var mem = GC.GetTotalMemory(true) / 1024.0 / 1024.0;
        Debug.WriteLine($"[{context}] Memory: {mem:F2} MB");
    }
}

4. Resource Factory Pattern

Copypublic static class FrozenResources
{
    public static SolidColorBrush CreateBrush(Color color)
    {
        var brush = new SolidColorBrush(color);
        brush.Freeze();
        return brush;
    }

    public static Pen CreatePen(Color color, double thickness)
    {
        var pen = new Pen(CreateBrush(color), thickness);
        pen.Freeze();
        return pen;
    }
}