WPF DataGrid：滚动时减小列宽以适应其内容

WPF DataGrid: reduce column width to fit its content while scrolling(WPF DataGrid：滚动时减小列宽以适应其内容)

问题描述

当我滚动垂直滚动条时，DataGrid如果新的可见行中的内容较大并超过以前的列宽，DataGrid会自动扩展列宽。没关系。 但是，如果滚动所有较大的行，并且新的可见行的内容宽度较小，DataGrid不会减小列宽。有没有办法确定这一点？

附加的行为实现将非常棒。

代码提示：

 public partial class MainWindow
    {
        public MainWindow()
        {
            InitializeComponent();
            var persons = new List<Person>();
            for (var i = 0; i < 20; i++)
                persons.Add(new Person() {Name = "Coooooooooooooool", Surname = "Super"});
            for (var i = 0; i < 20; i++)
                persons.Add(new Person() {Name = "Cool", Surname = "Suuuuuuuuuuuuuuper"});
            for (var i = 0; i < 20; i++)
                persons.Add(new Person() {Name = "Coooooooooooooool", Surname = "Super"});
            DG.ItemsSource = persons;
        }

        public class Person
        {
            public string Name { get; set; }
            public string Surname { get; set; }
        }
    }

XAML：

<Window
    x:Class="WpfApp4.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="400"
    Height="200"
    mc:Ignorable="d">
    <Grid>
        <DataGrid
            x:Name="DG"
            CanUserAddRows="False"
            CanUserDeleteRows="False"
            CanUserReorderColumns="False"
            CanUserResizeColumns="False"
            CanUserResizeRows="False"
            CanUserSortColumns="False" />
    </Grid>
</Window>

推荐答案

将LoadingRow属性添加到您的数据网格：

   <DataGrid x:Name="DG"
        CanUserAddRows="False"
        CanUserDeleteRows="False"
        CanUserReorderColumns="False"
        CanUserResizeColumns="False"
        CanUserResizeRows="False"
        CanUserSortColumns="False" LoadingRow="DG_LoadingRow">
    </DataGrid>

然后添加此代码 在后面的代码中：

private void DG_LoadingRow(object sender, DataGridRowEventArgs e)
    {
        foreach (DataGridColumn c in DG.Columns)
            c.Width = 0;

        DG.UpdateLayout();

        foreach (DataGridColumn c in DG.Columns)
            c.Width = DataGridLength.Auto;
    }

这肯定不是最干净的解决方案，但它会在滚动时调整视图中的列的大小。

希望这能有所帮助。

---

您能将此包装到附加行为中吗？

1)第一个选项是使用附加属性。

public class DataGridHelper : DependencyObject
{
    public static readonly DependencyProperty SyncedColumnWidthsProperty =
        DependencyProperty.RegisterAttached(
          "SyncedColumnWidths",
          typeof(Boolean),
          typeof(DataGridHelper),
          new FrameworkPropertyMetadata(false,
              FrameworkPropertyMetadataOptions.AffectsRender,
              new PropertyChangedCallback(OnSyncColumnsChanged)
          ));

    private static void OnSyncColumnsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is DataGrid dataGrid)
        {
            dataGrid.LoadingRow += SyncColumnWidths;
        }
    }

    private static void SyncColumnWidths(object sender, DataGridRowEventArgs e)
    {
        var dataGrid = (DataGrid)sender;

        foreach (DataGridColumn c in dataGrid.Columns)
            c.Width = 0;

        e.Row.UpdateLayout();

        foreach (DataGridColumn c in dataGrid.Columns)
            c.Width = DataGridLength.Auto;
    }

    public static void SetSyncedColumnWidths(UIElement element, Boolean value)
    {
        element.SetValue(SyncedColumnWidthsProperty, value);
    }
}

用法

<DataGrid
    ext:DataGridHelper.SyncedColumnWidths="True"
    ... />

2)或者，行为提供更封装的方式来扩展功能(需要System.Windows.Interactivity)。

using System.Windows.Interactivity;

...

    public class SyncedColumnWidthsBehavior : Behavior<DataGrid>
    {
        protected override void OnAttached()
        {
            this.AssociatedObject.LoadingRow += this.SyncColumnWidths;
        }

        protected override void OnDetaching()
        {
            this.AssociatedObject.LoadingRow -= this.SyncColumnWidths;
        }

        private void SyncColumnWidths(object sender, DataGridRowEventArgs e)
        {
            var dataGrid = this.AssociatedObject;

            foreach (DataGridColumn c in dataGrid.Columns)
                c.Width = 0;

            e.Row.UpdateLayout();

            foreach (DataGridColumn c in dataGrid.Columns)
                c.Width = DataGridLength.Auto;
        }
    }

用法

xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

...

    <DataGrid
        ... >
        <i:Interaction.Behaviors>
            <ext:SyncedColumnWidthsBehavior />
        </i:Interaction.Behaviors>
    </DataGrid>

行为为释放事件处理程序提供了一种干净的方式。尽管在这种情况下，即使我们没有取消订阅附加的属性，也不会造成内存泄漏(refIs it bad to not unregister event handlers?)。

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