我有一个图形项和矩阵项。图形项目是画布，我画椭圆和线。在矩阵项I中包含矩阵。我使用了这个库（xmlns：dg 2d =“clr-namespace：DataGrid 2DLibrary; assembly= DataGrid 2DLibrary”）（http://www.mediafire.com/?tm1arm230rr1tgi）将我的二维矩阵绑定到datagrid。但我注意到，在我点击矩阵项目之前，只要程序刚刚开始，我的意思是首先我与图形工作。Canvas绘制速度非常快，但在我点击矩阵项和itemsource后，当我再次返回图形时，它绘制得非常慢。另外，我注意到itemssource之后有很多内存。
在这段代码中，我尝试空ItemsSource并清除内存
MainWindow.xaml.cs

private void MatrixData(object sender, RoutedEventArgs e)
        {
            if (MatrixMenu.IsChecked)
            {
                if (DrawingCanvas_Undirected.Visibility == Visibility.Visible || DrawingCanvas_Directed.Visibility == Visibility.Visible)
                {
                    GraphItem.Visibility = Visibility.Visible;
                }

                MatrixItem.Visibility = Visibility.Collapsed;

                MatrixAdj.ItemsSource2D = null;
                MatrixInc.ItemsSource2D = null;
                MatrixMenu.IsChecked = false;
                GC.Collect();

            }

MainWindow.xaml

<Grid x:Name="MatrixItem" Visibility ="Collapsed">
            <Grid.RowDefinitions>
                <RowDefinition Height="149*"/>
                <RowDefinition Height="285*"/>
            </Grid.RowDefinitions>
            <Canvas>
                <dg2d:DataGrid2D x:FieldModifier="public" x:Name="MatrixAdj" 
                     VirtualizingPanel.IsVirtualizingWhenGrouping="True"
                     Canvas.Left="411" Canvas.Top="20"
                     Width="350" Height="289"
                     AlternationCount="2"
                     UseModifiedDataGridStyle="True"
                     ItemsSource2D="{Binding Int2DList}"
                     RowBackground="White"
                     AlternatingRowBackground="#ebebeb"                       
                     Background="Transparent" HorizontalAlignment="Left" VerticalAlignment="Center" />

            </Canvas>
            <Canvas Margin="4,2,-4,265" Grid.RowSpan="2">
                <dg2d:DataGrid2D x:FieldModifier="public" x:Name="MatrixInc" 
                             Canvas.Left="19" Canvas.Top="20"
                             Width="350" Height="289"
                             AlternationCount="2"
                             UseModifiedDataGridStyle="True"
                             ItemsSource2D="{Binding Int2DList}"
                             RowBackground="White"
                             VirtualizingPanel.IsVirtualizingWhenGrouping="True"
                             AlternatingRowBackground="#ebebeb"                       
                             Background="Transparent" Grid.RowSpan="2" HorizontalAlignment="Left" VerticalAlignment="Center"/>
            </Canvas>
</Grid>

所以问题是：点击矩阵项后如何保存画布绘制速度？