Question

我使用此代码将图像从二进制转换为图像。

public class ImageConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var memStream = new MemoryStream(((MeetPoint_B2C.ServiceReference1.Binary)value).Bytes);
        memStream.Seek(0, SeekOrigin.Begin);
        var empImage = new BitmapImage();
        empImage.CreateOptions = BitmapCreateOptions.None;
        empImage.SetSource(memStream);
        return empImage;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

从我的数据库加载超过20张图片时出错。这是异常未处理。请求不受支持。我认为内存流已经完整了。那么如何重置内存流呢？我知道可以使用dispose()或memorystream.setLength到0，但我应该如何或在何处进行编码？

例外细节

System.OutOfMemoryException was unhandled
  Message=OutOfMemoryException
  StackTrace:
       at MS.Internal.FrameworkCallbacks.NotifyManagedDebuggerOnNativeOOM()
       at MS.Internal.XcpImports.BitmapSource_SetSourceNative(IntPtr bitmapSource, CValue& byteStream)
       at MS.Internal.XcpImports.BitmapSource_SetSource(BitmapSource bitmapSource, CValue& byteStream)
       at System.Windows.Media.Imaging.BitmapSource.SetSourceInternal(Stream streamSource)
       at System.Windows.Media.Imaging.BitmapImage.SetSourceInternal(Stream streamSource)
       at System.Windows.Media.Imaging.BitmapSource.SetSource(Stream streamSource)
       at MeetPoint_B2C.ImageConverter.Convert(Object value, Type targetType, Object parameter, CultureInfo culture)
       at System.Windows.Data.BindingExpression.ConvertToTarget(Object value)
       at System.Windows.Data.BindingExpression.GetValue(DependencyObject d, DependencyProperty dp)
       at System.Windows.DependencyObject.EvaluateExpression(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry)
       at System.Windows.DependencyObject.EvaluateBaseValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
       at System.Windows.DependencyObject.EvaluateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry newEntry, ValueOperation operation)
       at System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
       at System.Windows.DependencyObject.RefreshExpression(DependencyProperty dp)
       at System.Windows.Data.BindingExpression.RefreshExpression()
       at System.Windows.Data.BindingExpression.SendDataToTarget()
       at System.Windows.Data.BindingExpression.SourceAcquired()
       at System.Windows.Data.BindingExpression.System.Windows.IDataContextChangedListener.OnDataContextChanged(Object sender, DataContextChangedEventArgs e)
       at System.Windows.Data.BindingExpression.DataContextChanged(Object sender, DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.OnDataContextChanged(DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.OnAncestorDataContextChanged(DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.NotifyDataContextChanged(DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.OnAncestorDataContextChanged(DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.NotifyDataContextChanged(DataContextChangedEventArgs e)
       at System.Windows.FrameworkElement.OnTreeParentUpdated(DependencyObject newParent, Boolean bIsNewParentAlive)
       at System.Windows.DependencyObject.UpdateTreeParent(IManagedPeer oldParent, IManagedPeer newParent, Boolean bIsNewParentAlive, Boolean keepReferenceToParent)
       at MS.Internal.FrameworkCallbacks.ManagedPeerTreeUpdate(IntPtr oldParentElement, IntPtr parentElement, IntPtr childElement, Byte bIsParentAlive, Byte bKeepReferenceToParent, Byte bCanCreateParent)
       at MS.Internal.XcpImports.Measure_WithDesiredSizeNative(IntPtr element, Single inWidth, Single inHeight, Single& outWidth, Single& outHeight)
       at MS.Internal.XcpImports.UIElement_Measure_WithDesiredSize(UIElement element, Size availableSize)
       at System.Windows.UIElement.Measure_WithDesiredSize(Size availableSize)
       at System.Windows.Controls.VirtualizingStackPanel.MeasureChild(UIElement child, Size layoutSlotSize)
       at System.Windows.Controls.VirtualizingStackPanel.MeasureOverride(Size constraint)
       at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Double inWidth, Double inHeight, Double& outWidth, Double& outHeight)
       at MS.Internal.XcpImports.MeasureOverrideNative(IntPtr element, Single inWidth, Single inHeight, Single& outWidth, Single& outHeight)
       at MS.Internal.XcpImports.FrameworkElement_MeasureOverride(FrameworkElement element, Size availableSize)
       at System.Windows.FrameworkElement.MeasureOverride(Size availableSize)
       at System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Double inWidth, Double inHeight, Double& outWidth, Double& outHeight)

以下.xaml

使用此功能

<Grid.Resources>
   <src:ImageConverter x:Key="imgConverter"/>
</Grid.Resources>
<Image Grid.Column="1" Grid.Row="4" Height="136" HorizontalAlignment="Left"
    Margin="16,16,0,0" Name="imgEmp" Stretch="Fill"
    VerticalAlignment="Top" Width="200"
    Source="{Binding Image, Converter={StaticResource imgConverter}}"/>

Answer 1

由于BitmapImage对象拥有流的所有权，您将无法正确关闭（或处置）它，因此我建议采用以下方式：

public BitmapImage Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
{ 
    var empImage = new BitmapImage(); 
    empImage.CreateOptions = BitmapCreateOptions.None; 
    empImage.SetSource(new MemoryStream(((MeetPoint_B2C.ServiceReference1.Binary)value).Bytes); ); 
    return empImage; 
}

在调用方法中，实现自己的资源清理。 BitmapImage不实现IDisposable，因此不能使用using语句。当Microsoft明确包含对非托管资源的引用时，Microsoft应考虑实现IDisposable：

public void ConvertBitmap()
{
    BitmapImage img = null;
    try
    {
        img = Convert(// pass in your params);

        // do stuff with your img
    }
    finally
    {
        // dispose of the memorystream in case of exception
        if(img != null && img.StreamSource != null) img.StreamSource.Dispose();
    }
}

这将确保即使在例外的情况下也能正确清理原始MemoryStream。

Answer 2

每次要求转换时，您已经创建了新的MemoryStream - 尽管在这种情况下您不需要寻求。您无需重置任何内容。

你应该真正找到完全抛出什么异常 - 它可能 nothing 与内存不足有关。您已编辑问题以显示堆栈跟踪，但不会抛出异常类型。一种可能性是它与在WCF服务中使用WPF控件有关，如果你的问题标签是任何东西。

编辑：请注意，即使您不想处置MemoryStream，也应确保在完成后处置BitmapImage结果用它。不幸的是，我们没有足够的背景知道你正在做什么来提供任何建议。

如何清除内存流

2 个答案: