Question

I’ve run into a situation where I’m leaking unmanaged memory when the mouse is moved over my WPF app. Specifically, when I profile the application in perfmon or Red Gate’s memory profiler, the private bytes monotonically increase, but the bytes in all managed heaps stay constant — which, I believe, means that the app has an unmanaged leak.

I’ve created a trivial repro app, but I can’t see where the problem is.

The app consists of a ListView with four items. Moving the mouse rapidly over these items causes the problem.

Here is the code if you’re interested in reproducing the issue — it’s not pretty, but it’s simple.

Thanks

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edit: I’ve created a Microsoft Connect issue for this problem.

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App.xaml

<Application x:Class="WpfLeakRepro.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    StartupUri="Window1.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Generic.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

App.xaml.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Windows;

namespace WpfLeakRepro
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
    }
}

Generic.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <LinearGradientBrush x:Key="ListItemHover"
                         EndPoint="0,1"
                         StartPoint="0,0">
        <GradientStop Color="Aqua"
                      Offset="0" />
        <GradientStop Color="White"
                      Offset="1" />
    </LinearGradientBrush>
    <LinearGradientBrush x:Key="ListItemSelected"
                         EndPoint="0,1"
                         StartPoint="0,0">
        <GradientStop Color="Blue"
                      Offset="0" />
        <GradientStop Color="White"
                      Offset="1" />
    </LinearGradientBrush>
    <VisualBrush x:Key="CheckeredBackground"
                 Viewport="20,20,20,20"
                 ViewportUnits="Absolute"
                 TileMode="Tile"
                 Stretch="Fill">
        <VisualBrush.Visual>
            <Canvas Opacity="5">
                <Rectangle Fill="#FF606060"
                           Height="21"
                           Width="21"
                           Canvas.Top="20" />
                <Rectangle Fill="#FF606060"
                           Width="21"
                           Height="21"
                           Canvas.Left="20" />
                <Rectangle Fill="#FF646464"
                           Height="21"
                           Width="21"
                           Canvas.Left="20"
                           Canvas.Top="20" />
                <Rectangle Fill="#FF646464"
                           Width="21"
                           Height="21" />
            </Canvas>
        </VisualBrush.Visual>
    </VisualBrush>
    <Style TargetType="{x:Type ListViewItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ListViewItem}">
                    <Border Background="{TemplateBinding Background}">
                        <Grid>
                            <GridViewRowPresenter />
                        </Grid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver"
                                 Value="true">
                            <Setter Property="Background"
                                    Value="{DynamicResource ListItemHover}" />
                        </Trigger>
                        <Trigger Property="IsSelected"
                                 Value="true">
                            <Setter Property="Background"
                                    Value="{DynamicResource ListItemSelected}" />
                        </Trigger>
                    </ControlTemplate.Triggers>

                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

Window1.xaml

<Window x:Class="WpfLeakRepro.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="449" Width="497">
    <Grid>
        <ListView Margin="12"
                  Name="listView"
                  ItemsSource="{Binding}">
            <ListView.View>
                <GridView>
                    <GridView.Columns>
                        <GridViewColumn Header="File Name">
                            <GridViewColumn.CellTemplate>
                                <DataTemplate>
                                    <TextBlock Text="{Binding Name}" />
                                </DataTemplate>
                            </GridViewColumn.CellTemplate>
                        </GridViewColumn>
                        <GridViewColumn Header="Thumbnail">
                            <GridViewColumn.CellTemplate>
                                <DataTemplate>
                                    <Border Background="{DynamicResource CheckeredBackground}" Width="72" Height=48/>
                                </DataTemplate>
                            </GridViewColumn.CellTemplate>
                        </GridViewColumn>
                    </GridView.Columns>
                </GridView>
            </ListView.View>
        </ListView>
    </Grid>
</Window>

Window1.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.IO;

namespace WpfLeakRepro
{
    public class Picture
    {
        public string Name { get; set; }
    }

    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            List<Picture> pictures = new List<Picture>();

            string[] images = new string[] {"Blue hills.jpg", "Sunset.jpg", "Water lilies.jpg", "Winter.jpg" };

            foreach (string imagePath in images)
            {
                pictures.Add(new Picture() { Name = imagePath });
            }

            DataContext = pictures;
        }
    }
}

Answer 1

The issue appears to have something to do with the VisualBrush that was being used for the checkered background. Replace this with a SolidColorBrush, and the issue goes away. But it really doesn’t matter: the folks at Microsoft suggested that I install the latest upgrades to .NetFx 3.5sp1, and this seems to fix the problem (more details here).