c# – WPF DataBinding当我使用Convert来格式化日期时非常慢

2023年1月11日 165次阅读

我正在编写一个简单的应用程序来显示DataGrid上的一些数据.数据只是一个度量(浮点数)和一个时间戳.时间戳是一个uint,自2000年以来以秒为单位.

我成功地完成了任务,但确实注意到显示数据网格需要很长时间(约1分钟).大约有20,000个数据.我不认为20,000个由uint和float组成的数据就是那么简单.下一个请求是将时间显示为格式化时间而不是自2000年以来的秒数.这是通过使XAML看起来像这样：

<kit:DataGridTextColumn Header="FilteredValue" Binding="{Binding Path=FilteredValue}" />
<kit:DataGridTextColumn Header="Timestamp" Binding="{Binding Path=Timestamp, Converter={StaticResource TimeConverter}}" CanUserSort="False" />

TimeConverter方法如下所示：

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    DateTime currentDateTime = new DateTime(2000, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    currentDateTime = currentDateTime.AddSeconds((uint)value);
    return currentDateTime.ToString();                  
}

这也很好.但是,事实证明一些原始数据可以是0xFFFFFFFF.
这意味着没有数据或无效数据.在这种情况下,我不想转换为日期.所以我写道：

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{

    if ((uint)value == 0xFFFFFFFF)
    {
    // don't bother to convert
    return ((uint)value).ToString("X");
    }
   else
   {
    DateTime currentDateTime = new DateTime(2000, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    currentDateTime = currentDateTime.AddSeconds((uint)value);
    return currentDateTime.ToString();
   }

}

它再次起作用,但速度很慢.比原来慢,大约需要10分钟.我很惊讶这一点.这是多少代码运行23,000次的情况吗？
1.我该怎么办？我可以在XAML中执行某些操作,以便在没有必要时调用我的Converter吗？
2.当我有一个测量值(FilteredValues)的0xFFFFFFFF时,它显示为NaN.这可能没问题,但只显示0xFFFFFFFF或“无数据”会很好.我认为它已设置为NaN,因为底层数据类型是浮点数.

有任何想法吗？

谢谢,
戴夫

这是XAML.最后一个Datagrid是感兴趣的.请注意,我甚至将“IsVirtualizing”设置为True.还要注意使用ScrollViewer.我这样做是因为否则我无法看到最后一个网格上的所有行(最终显示).删除它并没有加快速度.

<Window x:Class="STDatabaseReader.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:chartingToolkit="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit" xmlns:kit="http://schemas.microsoft.com/wpf/2008/toolkit" xmlns:local="clr-namespace:STDatabaseReader"
    Title="Smart Transmitter Database Reader">
<Window.Resources>

    <local:BytesToStringConverter x:Key="BytesToStringConverter"></local:BytesToStringConverter>
    <local:TimeConverter x:Key="TimeConverter"></local:TimeConverter>
</Window.Resources>

<Grid>
     <ScrollViewer>    
        <StackPanel Orientation="Vertical">
            <Button Name="m_btnFetchData" HorizontalAlignment="Left" Click="m_btnFetchData_Click">Fetch File</Button>
            <StackPanel Orientation="Horizontal">

                <StackPanel Orientation="Vertical">
                    <Label HorizontalAlignment="Center">Partition 1</Label>
                    <kit:DataGrid Name="m_gridPartion1" AutoGenerateColumns="False">
                        <kit:DataGrid.Columns>
                            <kit:DataGridTextColumn Header="Header Info" Binding="{Binding Path=HeaderInfo, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />
                            <kit:DataGridTextColumn Header="Transmitter Id" Binding="{Binding Path=TransmitterId, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />
                            <kit:DataGridTextColumn Header="DeviceNumber" Binding="{Binding Path=DeviceNumber}" />
                            <kit:DataGridTextColumn Header="HardwareVersion" Binding="{Binding Path=HardwareVersion}" />
                            <kit:DataGridTextColumn Header="CRC" Binding="{Binding Path=CRC}" />
                        </kit:DataGrid.Columns>
                    </kit:DataGrid>
                </StackPanel>

                <StackPanel Orientation="Vertical">
                    <Label HorizontalAlignment="Center">Partition 3</Label>
                    <kit:DataGrid Name="m_gridPartion3" AutoGenerateColumns="False">
                        <kit:DataGrid.Columns>
                            <kit:DataGridTextColumn Header="Header Info" Binding="{Binding Path=HeaderInfo, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />
                            <kit:DataGridTextColumn Header="SystemTime" Binding="{Binding Path=SystemTime, Converter={StaticResource TimeConverter}}" />
                        </kit:DataGrid.Columns>
                    </kit:DataGrid>
                </StackPanel>
            </StackPanel>
            <StackPanel Orientation="Vertical">
                <Label HorizontalAlignment="Center">Partition 2</Label>
                <kit:DataGrid Name="m_gridPartion2" AutoGenerateColumns="False">
                    <kit:DataGrid.Columns>
                        <kit:DataGridTextColumn Header="Header Info" Binding="{Binding Path=HeaderInfo, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />

                        <kit:DataGridTextColumn Header="FirmwareRevision" Binding="{Binding Path=FirmwareRevision, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />

                        <kit:DataGridTextColumn Header="SoftwarePartNumber" Binding="{Binding Path=SoftwarePartNumber, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />

                        <kit:DataGridTextColumn Header="FirmwareUpgradeTime" Binding="{Binding Path=FirmwareUpgradeTime,Converter={StaticResource TimeConverter}}" />
                        <kit:DataGridTextColumn Header="DatabaseEraseTime" Binding="{Binding Path=DatabaseEraseTime,Converter={StaticResource TimeConverter}}" />
                        <kit:DataGridTextColumn Header="RangeEnzymeElectrode" Binding="{Binding Path=RangeEnzymeElectrode}" />
                        <kit:DataGridTextColumn Header="OffsetEnzymeElectrode" Binding="{Binding Path=OffsetEnzymeElectrode}" />
                        <kit:DataGridTextColumn Header="BiasValue" Binding="{Binding Path=BiasValue}" />
                    </kit:DataGrid.Columns>
                </kit:DataGrid>
            </StackPanel>

            <StackPanel Orientation="Horizontal">
                <StackPanel Orientation="Vertical">
                    <Label HorizontalAlignment="Center">Partition 4 - HeaderInfo</Label>
                    <kit:DataGrid Name="m_gridDataHeader" AutoGenerateColumns="False">
                        <kit:DataGrid.Columns>
                            <kit:DataGridTextColumn Header="Header Info" Binding="{Binding Path=HeaderInfo, Converter={StaticResource BytesToStringConverter}}" CanUserSort="False" />
                        </kit:DataGrid.Columns>
                    </kit:DataGrid>
                </StackPanel>
                <StackPanel   Orientation="Vertical">
                    <Label HorizontalAlignment="Center">Partition 4 - Chemistry Data</Label>

                        <kit:DataGrid Name="m_gridData" AutoGenerateColumns="False" VirtualizingStackPanel.IsVirtualizing="True"  Loaded="m_gridData_Loaded">
                            <kit:DataGrid.Columns>
                                <!--
                                <kit:DataGridTextColumn Header="Noise" Binding="{Binding Path=Noise, StringFormat=\{0:X8\}}" />
                                <kit:DataGridTextColumn Header="FilteredValue" Binding="{Binding Path=FilteredValue, StringFormat='X'}" />
                                 <kit:DataGridTextColumn Header="Timestamp" Binding="{Binding Path=Timestamp, StringFormat=\{0:X\}}" />   -->
                            <kit:DataGridTextColumn Header="Noise" Binding="{Binding Path=Noise}" />
                            <kit:DataGridTextColumn Header="FilteredValue" Binding="{Binding Path=FilteredValue}" />
                            <kit:DataGridTextColumn Header="Timestamp" Binding="{Binding Path=Timestamp, Converter={StaticResource TimeConverter}}" CanUserSort="False" />
                        </kit:DataGrid.Columns>
                        </kit:DataGrid>

                </StackPanel >
            </StackPanel>
        </StackPanel>
     </ScrollViewer>     
</Grid>

最佳答案由于该列是DataGridTextColumn,您可以通过在转换器中返回它来显示0xFFFFFFFF

if ((uint)value == 0xFFFFFFFF)
{
    // don't bother to convert
    return "0xFFFFFFFF";
}

至于DataGrid很慢,它应该默认使用VirtualizingStackPanel,所以如果你没有改变它,那么它应该非常快,因为你只会使用目前对用户可见的DataGridRows.此外,转换器中的代码几乎没有时间.

因此,你的DataGrid变慢的最可能的原因可能是你已经将ItemsPanel更改为VirtualizingStackPanel以外的其他东西,或者以某种方式禁用了虚拟化,但是如果没有看到你的DataGrid是如何定义的话很难说清楚

编辑
在DataGrid完成加载后运行以下代码,例如在DataGrid的Loaded事件中.如果MessageBox显示一个大数字(不应超过50),那么您就有问题的根源.

private void DataGrid_Loaded(object sender, RoutedEventArgs e)
{
    DataGrid dataGrid = sender as DataGrid;
    List<DataGridRow> generatedDataGridRows = VisualTreeHelpers.GetVisualChildCollection<DataGridRow>(dataGrid);
    MessageBox.Show(generatedDataGridRows.Count.ToString());
}
public static List<T> GetVisualChildCollection<T>(object parent) where T : Visual
{
    List<T> visualCollection = new List<T>();
    GetVisualChildCollection(parent as DependencyObject, visualCollection);
    return visualCollection;
}
private static void GetVisualChildCollection<T>(DependencyObject parent, List<T> visualCollection) where T : Visual
{
    int count = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < count; i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(parent, i);
        if (child is T)
        {
            visualCollection.Add(child as T);
        }
        else if (child != null)
        {
            GetVisualChildCollection(child, visualCollection);
        }
    }
}

例如,使用StackPanel作为父面板将非常慢,因为DataGrid可以消耗无限的垂直空间,因此将生成所有行

<StackPanel>
    <!-- Slow DataGrid with 20000+ items in ItemsSource -->
    <DataGrid ...>
</StackPanel>

但是使用网格会非常快,因为DataGrid的高度会受到限制,因此可以使用虚拟化

<Grid>
    <!-- Fast DataGrid with 20000+ items in ItemsSource -->
    <DataGrid ...>
</Grid>