WPF中实现DataGrid行拖拽功能的完整方案

目录

• 前言
• 实现效果
• 核心实现
• 1、定义拖拽行为类
• 2、UI工具类
• 3、XAML中使用
• 实现原理
• 关键特性
• 总结

前言

在wpF应用开发中，DataGrid是一个常用的数据展示控件。然而，原生的DataGrid并不支持行拖拽功能，这在需要调整行顺序的场景中显得尤为不便。

本文将介绍如何实现一个优雅的DataGrid行拖拽功能，使用户可以通过拖拽操作轻松调整行顺序。该方案基于开源项目实现，使用MIT协议的HandyControl样式库，具有良好的可扩展性和实用性。

实现效果

核心实现

1、定义拖拽行为类

public static class DragDropRowBehavior
{
    private static DataGrid dataGrid;
    private static Popup popup;
    private static bool enable;
    private static object draggedItem;

    public static object DraggedItem
    {
        get { return DragDropRowBehavior.draggedItem; }
        set { DragDropRowBehavior.draggedItem = value; }
    }

    // 定义PopupControl附加属性
    public static readonly Depend编程客栈encyProperty PopupControlProperty =
        DependencyProperty.RegisterAttached("PopupControl", typeof(Popup), 
            typeof(DragDropRowBehavior), new UIPropertyMetadata(null, OnPopupControlChanged));

    public static Popup GetPopupControl(DependencyObject obj)
    {
        return (Popup)obj.GetValue(PopupControlProperty);
    }

    public static void SetPopupControl(DependencyObject obj, Popup value)
    {
        obj.SetValue(PopupControlProperty, value);
    }

    private static void OnPopupControlChanged(DependencyObject depObject, DependencyPropertyChangedEventArgs e)
    {
        if (e.NewValue == null || !(e.NewValue is Popup))
        {
            throw new ArgumentException("Popup Control should be set", "PopupControl");
        }
        popup = e.NewValue as Popup;

        dataGrid = depObject as DataGrid;
        if (dataGrid == null) return;

        if (enable && popup != null)
        {
            dataGrid.BeginningEdit += OnBeginEdit;
            dataGrid.CellEditEnding += OnEndEdit;
            dataGrid.MouseLeftButtonUp += OnMouseLeftButtonUp;
            dataGrid.PreviewMouseLeftButtonDown += OnMouseLeftButtonDown;
            dataGrid.MouseMove += OnMouseMove;
        }
        else
        {
       编程客栈     dataGrid.BeginningEdit -= OnBeginEdit;
            dataGrid.CellEditEnding -= OnEndEdit;
            dataGrid.MouseLeftButtonUp -= OnMouseLeftButtonUp;
            dataGrid.MouseLeftButtonDown -= OnMouseLeftButtonDown;
            dataGrid.MouseMove -= OnMouseMove;

            dataGrid = null;
            popup = null;
            draggedItem = null;
            IsEditing = false;
            IsDragging = false;
        }
    }

    // 定义Enabled附加属性
    public static readonly DependencyProperty EnabledProperty =
        DependencyProperty.RegisterAttpythonached("Enabled", typeof(bool), 
            typeof(DragDropRowBehavior), new UIPropertyMetadata(false, OnEnabledChanged));

    public static bool GetEnabled(DependencyObject obj)
    {
        return (bool)obj.GetValue(EnabledProperty);
    }

    public static void SetEnabled(DependencyObject obj, bool value)
    {
        obj.SetValue(EnabledProperty, value);
    }

    private static void OnEnabledChanged(DependencyObject depObject, DependencyPropertyChangedEventwww.devze.comArgs e)
    {
        if (e.NewValue is bool == false)
            throw new ArgumentException("Value should be of bool type", "Enabled");

        enable = (bool)e.NewValue;
    }

    public static bool IsEditing { get; set; }
    public static bool IsDragging { get; set; }

    private static void OnBeginEdit(object sender, DataGridBeginningEditEventArgs e)
    {
        IsEditing = true;
        if (IsDragging) ResetDragDrop();
    }

    private static void OnEndEdit(object sender, DataGridCellEditEndingEventArgs e)
    {
        IsEditing = false;
    }

    private static void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        if (IsEditing) return;
        
        var row = UIHelpers.TryFindFromPoint<DataGridRow>((UIElement)sender, e.GetPosition(dataGrid));
        if (row == null || row.IsEditing) return;

        IsDragging = true;
        DraggedItem = row.Item;
    }

    private static void OnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        if (!IsDragging || IsEditing) return;
        
        dataGrid.Cursor = Cursors.Arrow;
        var targetItem = dataGrid.SelectedItem;

        if (targetItem == null || !ReferenceEquals(DraggedItem, targetItem))
        {
            var targetIndex = ((dataGrid).ItemsSource as IList).IndexOf(targetItem);
            ((dataGrid).ItemsSource as IList).Remove(DraggedItem);
            ((dataGrid).ItemsSource as IList).Insert(targetIndex, DraggedItem);
            dataGrid.SelectedItem = DraggedItem;
        }

        ResetDragDrop();
    }

    private static void ResetDragDrop()
    {
        IsDragging = false;
        popup.IsOpen = false;
        dataGrid.IsReadOnly = false;
    }

    private static void OnMouseMove(object sender, MouseEventArgs e)
    {
        if (!IsDragging || e.LeftButton != MouseButtonState.Pressed) return;
        
        if (dataGrid.Cursor != Cursors.SizeAll) dataGrid.Cursor = Cursors.SizeAll;
        
        popup.DataContext = DraggedItem;
        
        if (!popup.IsOpen)
        {
            dataGrid.IsReadOnly = true;
            popup.IsOpen = true;
        }

        Size popupSize = new Size(popup.ActualWidth, popup.ActualHeight);
        popup.PlacementRectangle = new Rect(e.GetPosition(dataGrid), popupSize);

        Point position = e.GetPosition(dataGrid);
        var row = UIHelpers.TryFindFromPoint<DataGridRow>(dataGrid, position);
        if (row != null) dataGrid.SelectedItem = row.Item;
    }
}

2、UI工具类

public static class UIHelpers
{
    // 查找父元素
    public static T TryFindParent<T>(DependencyObject child) where T : DependencyObject
    {
        DependencyObject parentObject = GetParentObject(child);
        if (parentObject == null) return null;
        
        T parent = parentObject as T;
        if (parent != null) return parent;
        else return TryFindParent<T>(parentObject);
    }

    public static DependencyObject GetParentObject(DependencyObject child)
    {
        if (child == null) return null;
        
        if (child is ContentElement contentElement)
        {
            DependencyObject parent = ContentOperations.GetParent(contentElement);
            if (parent != null) return parent;

            if (contentElement is FrameworkContentElement fce) 
                return fce.Parent;
        }
        
        return VisualTreeHelper.GetParent(child);
    }

    // 更新绑定源
    public static void UpdateBindingSources(DependencyObject obj, params DependencyProperty[] propepythonrties)
    {
        foreach (DependencyProperty depProperty in properties)
        {
            BindingExpression be = BindingOperations.GetBindingExpression(obj, depProperty);
            if (be != null) be.UpdateSource();
        }

        int count = VisualTreeHelper.GetChildrenCount(obj);
        for (int i = 0; i < count; i++)
        {
            DependencyObject childObject = VisualTreeHelper.GetChild(obj, i);
            UpdateBindingSources(childObject, properties);
        }
    }

    // 从指定点查找元素
    public static T TryFindFromPoint<T>(UIElement reference, Point point) where T : DependencyObject
    {
        DependencyObject element = reference.InputHitTest(point) as DependencyObject;
        if (element == null) return null;
        else if (element is T) return (T)element;
        else return TryFindParent<T>(element);
    }
}

3、XAML中使用

<Grid Grid.Row="1" Margin="5">
    <!-- 拖拽提示Popup -->
    <Popup x:Name="popup1" AllowsTransparency="True" 
           IsHitTestVisible="False" Placement="RelativePoint" 
           PlacementTarget="{Binding ElementName=dataGrid1}">
        <Textblock Margin="8,0,0,0" VerticalAlignment="Center" 
                   FontSize="14" FontWeight="Bold" Text="Dragging..." />
    </Popup>
    
    <!-- 启用拖拽行为的DataGrid -->
    <DataGrid x:Name="dataGrid1" 
              controlEx:DragDropRowBehavior.Enabled="True"
              controlEx:DragDropRowBehavior.PopupControl="{Binding ElementName=popup1}"
              AutoGenerateColumns="False" 
              ItemsSource="{Binding ListItem}" 
              RowHeaderWidth="60">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding Column1}" Header="column1" />
            <DataGridTextColumn Binding="{Binding Column2}" Header="column2" />
            <DataGridTextColumn Binding="{Binding Column3}" Header="column3" />
        </DataGrid.Columns>
    </DataGrid>
</Grid>

实现原理

1、拖拽开始：用户按下鼠标左键时，记录被拖拽的行（OnMouseLeftButtonDown）

2、拖拽过程：鼠标移动时显示提示Popup并更新位置（OnMouseMove）

3、拖拽结束：释放鼠标时交换行位置（OnMouseLeftButtonUp）

4、状态管理：使用IsEditing和IsDragging标志管理编辑与拖拽状态

5、UI辅助：通过UIHelpers类在可视化树中查找元素

关键特性

可视化反馈：拖拽时显示"Dragging..."提示

编辑支持：编辑状态下自动禁用拖拽功能

平滑交互：拖拽过程中光标自动切换为"SizeAll"样式

行定位：自动定位鼠标悬停位置的行

总结

本文介绍了WPF DataGrid行拖拽功能的完整实现方案。该方案通过附加行为的方式扩展了DataGrid的功能，使其支持行拖拽操作。

关键点包括：

1、使用附加属性实现功能解耦

2、通过Popup提供拖拽视觉反馈

3、利用UIHelpers工具类简化可视化树操作

4、正确处理编辑与拖拽的冲突

该实现方案具有较好的可复用性，只需在DataGrid上设置附加属性即可启用拖拽功能，无需修改原有业务逻辑。

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