不合理的WPF DataGrid加载时间

Question

我一直用WPF DataGrids加载时间很长,我在网上找不到任何类似的报道,所以我怀疑我做错了什么.现在我很确定,因为添加布局复杂性会大大降低执行速度.在一个非常简单的布局中,DataGrid立即填充,而下面的代码大约需要3秒才能执行.

在以下代码中,加载150行和11列需要约3秒,即使每个单元格未绑定到任何属性且AutoGenerateColumns = False也是如此.(我有一个两核,2.6GHz处理器,有足够的RAM).

如果在布局中设置ItemsSource属性,则会发生瓶颈,如下所示:

<Window x:Class="datagridtest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Border  Background="LightSteelBlue" CornerRadius="10" Margin="10">
    <ScrollViewer Margin="10" HorizontalScrollBarVisibility="Auto">
        <Grid Margin="10,50,0,0">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"  />
                <RowDefinition Height="auto" />
                <RowDefinition Height="auto" />

            </Grid.RowDefinitions>
            <Expander IsExpanded="True" Name="expander1"  Grid.Row="0">
                <Grid>
                    <DataGrid VirtualizingStackPanel.IsVirtualizing="True" AutoGenerateColumns="false" Name="dg" Height="auto" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserResizeRows="False" CanUserSortColumns="False">
                        <DataGrid.Columns>
                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>



                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>


                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>

                            <DataGridTextColumn >
                                <DataGridTextColumn.Header >
                                    <TextBlock Width="140" HorizontalAlignment="Center" TextAlignment="Center">untitled<LineBreak/>column</TextBlock>
                                </DataGridTextColumn.Header>
                            </DataGridTextColumn>



                        </DataGrid.Columns>
                        </DataGrid>
                </Grid>
            </Expander>

            <Expander IsExpanded="true"  Grid.Row="1">
                <Grid>
                    <DataGrid AutoGenerateColumns="True"  Height="auto" />
                </Grid>
            </Expander>

            <Expander IsExpanded="true"    Grid.Row="2">
                <Grid>
                    <DataGrid AutoGenerateColumns="True" Height="auto" />
                </Grid>
            </Expander>
            <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="121,-42,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click_2" />
        </Grid>
    </ScrollViewer>
</Border>

using System.Collections.ObjectModel;

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


    }

    class row
    {
        public string Name { get; set; }
        public double Age { get; set; }
    }



    private void button1_Click_2(object sender, RoutedEventArgs e)
    {
        ObservableCollection<row> src = new ObservableCollection<row>();

        for (int i = 0; i < 150; i++)
            src.Add(new row { Name = i.ToString(), Age = i / 2 });

        dg.ItemsSource = src;
    }
}
}

Answer 1

只有当DataGrid嵌入ScrollViewer时才会出现此问题:

<ScrollViewer>
    <Datagrid/>
</ScrollViewer>

这是有道理的,因为这种配置导致整个DataGrid同时被绘制(以便能够正确地调整ScrollViewer的客户区域的大小).实质上,它覆盖了DataGrid的内置虚拟化行为,DataGrid实现了自己的ScrollBars,因此并非所有内容都必须同时放在布局中.

换句话说,很少需要在ScrollViewer中嵌入DataGrid,因为DataGrid有自己的自动滚动.

Answer 2

我有一个包含DataGrid的UserControl的类似问题,有时当我将UserControl放在一个新窗体或另一个UserControl上时,它会在重绘DataGrid时锁定界面(5秒？).与调整大小相同.

我跟踪它

RowDefinition Height ="Auto"

如果我将UserControl放在StackPanel中,也会出现相同的性能问题.当需要弹出整个数据网格来计算封装容器的大小时,似乎与前面提到的调整大小错误有很大关系.

<UserControl x:Class="ExampleUserControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" d:DesignHeight="481" d:DesignWidth="773">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" /> <!-- 'AUTO' CAUSES EXTREMELY POOR PERFORMANCE -->
        </Grid.RowDefinitions>

        <Grid Grid.Row="0"> <!-- CHANGING TO STACKPANEL CAUSES EXTREMELY POOR PERFORMANCE -->
            <ContentControl Content="{Binding MyDataGridUserControl}" />
        </Grid>
    </Grid>

</UserControl>

我刚刚发现,根据之前的评论,为ContentControl设置MaxHeight ="[whatever]"也可以.它可以比屏幕大.