DevExpress WPF 15.2代码示例：如何为网格添加DragAndDrop功能

本来带有DataControlDetailDescriptor的detail网格是不支持拖放操作的，所以要实现这个功能，首先我们创建一个GridDragDropManager class，然后覆盖CalcDraggingRows method去获取一个选中的行。然后，应用到GridDragDropManager's DragOver and Drop。当鼠标拖动时，计算要插入选中行的位置。

代码：C#     版本：15.2.4

using DevExpress.Mvvm.UI;
using DevExpress.Xpf.Core.Native;
using DevExpress.Xpf.Grid;
using DevExpress.Xpf.Grid.DragDrop;
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Threading;

namespace DragAndDropExample
{
    class CustomGridDragAndDrop : GridDragDropManager 
    {
        public TableView TableView;
        public RowControl SourceRow;

        public CustomGridDragAndDrop()
        {
            Drop += CustomGridDragAndDrop_Drop;
            DragOver += CustomGridDragAndDrop_DragOver;
        }

        void CustomGridDragAndDrop_DragOver(object sender, GridDragOverEventArgs e)
        {
            var result = VisualTreeHelper.HitTest(this.View, Mouse.GetPosition(View));

            if (result != null && result.VisualHit != null)
            {
                var hitRow = LayoutTreeHelper.GetVisualParents(HitElement).Where(row => row is GroupGridRow || row is RowControl).FirstOrDefault() as FrameworkElement;   

                if (hitRow != null)
                {
                    var rowData = hitRow.DataContext as RowData;
                    e.AllowDrop = Equals(rowData.Row.GetType(), e.DraggedRows[0].GetType());
                    e.Handled = true;
                }
                else
                {
                    e.AllowDrop = false;
                    e.Handled = true;
                }
            }
        }

        protected override bool CanStartDrag(MouseButtonEventArgs e)
        {
            SourceRow = LayoutTreeHelper.GetVisualParents(e.OriginalSource as DependencyObject).Where(row => row is RowControl).FirstOrDefault() as RowControl;
            
            return base.CanStartDrag(e);
        }

        void CustomGridDragAndDrop_Drop(object sender, GridDropEventArgs e)
        {
            if (TableView != null)
            {
                DropRow(e);
                TableView = null;
                e.Handled = true;
            }
        }

        protected override IList CalcDraggingRows(DevExpress.Xpf.Core.IndependentMouseEventArgs e)
        {
            if (SourceRow != null)
            {
                var rowData = SourceRow.DataContext as RowData;

                TableView = rowData.View as TableView;

                return new List<object> { rowData.Row };
            }
            else return null;
        }


        public void DropRow(GridDropEventArgs args)
        {

            var currentRow = LayoutTreeHelper.GetVisualParents(HitElement).Where(row => row is GroupGridRow || row is RowControl).FirstOrDefault() as FrameworkElement;

            var rowData = currentRow.DataContext as RowData;

            var tableSource = TableView.Grid.ItemsSource as IList;
            var dataView = rowData.View as TableView;
            var dataSource = dataView.Grid.ItemsSource as IList;
            var rowIndex = dataView.Grid.GetListIndexByRowHandle(args.TargetRowHandle);

            var draggingRow = DraggingRows[0];

            if (dataSource == null || dataSource[0].GetType() != draggingRow.GetType() || dataSource.Count == 0 || draggingRow == rowData.Row)
            {
                return;
            }

            if (Equals(tableSource, dataSource) && tableSource.IndexOf(DraggingRows[0]) <= rowIndex)
            {
                rowIndex--;
            }

            tableSource.Remove(DraggingRows[0]);

            if (!dataView.Grid.IsGrouped)
            {
                if (args.DropTargetType == DropTargetType.InsertRowsBefore)
                {
                    dataSource.Insert(rowIndex, draggingRow);
                }
                else if (args.DropTargetType == DropTargetType.InsertRowsAfter)
                {
                    dataSource.Insert(Math.Min(rowIndex + 1, dataSource.Count), draggingRow);
                }
                else
                {
                    if (Mouse.GetPosition(currentRow).Y >= currentRow.ActualHeight / 2)
                        dataSource.Insert(Math.Min(rowIndex + 1, dataSource.Count), draggingRow);
                    else dataSource.Insert(rowIndex, draggingRow);
                }
            }
            else if (args.DropTargetType == DropTargetType.InsertRowsIntoGroup || dataView.Grid.IsGrouped)
            {
                var value = dataView.Grid.GetCellValue(rowData.RowHandle.Value, dataView.Grid.SortInfo[0].FieldName);

                TypeDescriptor.GetProperties(draggingRow.GetType())[dataView.Grid.SortInfo[0].FieldName].SetValue(draggingRow, value);

                if (args.DropTargetType == DropTargetType.InsertRowsAfter)
                {
                    dataSource.Insert(Math.Min(rowIndex + 1, dataSource.Count), draggingRow);
                }
                else dataSource.Insert(rowIndex, draggingRow);

                dataView.Grid.RefreshData();
            }
        }

        static MethodInfo IsSameGroupInfo = typeof(GridDragDropManager).GetMethod("IsSameGroup", BindingFlags.NonPublic | BindingFlags.Instance);
        protected bool IsSameGroup(DragDropManagerBase sourceManager, GroupInfo[] groupInfos, DependencyObject hitElement)
        {
            return (bool)IsSameGroupInfo.Invoke(this, new object[] { sourceManager, groupInfos, hitElement });
        }

        static MethodInfo GetGroupInfosInfo = typeof(GridDragDropManager).GetMethod("GetGroupInfos", BindingFlags.NonPublic | BindingFlags.Instance);
        protected GroupInfo[] GetGroupInfos(int rowHandle)
        {
            return (GroupInfo[])GetGroupInfosInfo.Invoke(this, new object[] { rowHandle });
        }

        static MethodInfo SetReorderDropInfoInfo = typeof(GridDragDropManager).GetMethod("SetReorderDropInfo", BindingFlags.NonPublic | BindingFlags.Instance);
        protected void SetReorderDropInfo(DragDropManagerBase sourceManager, int insertRowHandle, DependencyObject hitElement)
        {
            SetReorderDropInfoInfo.Invoke(this, new object[] { sourceManager, insertRowHandle, hitElement });
        }

        static MethodInfo SetMoveToGroupRowDropInfoInfo = typeof(GridDragDropManager).GetMethod("SetMoveToGroupRowDropInfo", BindingFlags.NonPublic | BindingFlags.Instance);

        protected void SetMoveToGroupRowDropInfo(DragDropManagerBase sourceManager, int insertRowHandle, DependencyObject hitElement)
        {
            SetReorderDropInfoInfo.Invoke(this, new object[] { sourceManager, insertRowHandle, hitElement });
        }

        protected bool IsGrouped(GridControl grid)
        {
            return grid.GroupCount > 0;
        }
        protected bool IsSorted(GridControl grid)
        {
            return grid.SortInfo.Count > 0;
        }
        protected bool IsSortedButNotGrouped(GridControl grid)
        {
            return IsSorted(grid) && !IsGrouped(grid);
        }
        protected bool ShouldReorderGroup(GridControl grid)
        {
            return grid.SortInfo.Count <= grid.GroupCount;
        }

        protected override void PerformDropToViewCore(DragDropManagerBase sourceManager)
        {
            GridViewHitInfoBase hitInfo = GetHitInfo(HitElement);
            if (BanDrop(hitInfo.RowHandle, hitInfo, sourceManager, DropTargetType.None))
            {
                ClearDragInfo(sourceManager);
                return;
            }
            PerformDropToView(sourceManager, hitInfo as TableViewHitInfo, LastPosition, SetReorderDropInfo, (_) => SetMoveToGroupRowDropInfo, SetAddRowsDropInfo);
        }

        protected GridControl GetSourceGrid()
        {
            var parentRow = (FrameworkElement)LayoutHelper.FindParentObject<RowControl>(HitElement) ?? (FrameworkElement)LayoutHelper.FindParentObject<GridRowContent>(HitElement);
            return parentRow != null ? ((RowData)parentRow.DataContext).View.DataControl as GridControl : this.GridControl;
        }

        protected void PerformDropToView(DragDropManagerBase sourceManager, TableViewHitInfo hitInfo, Point pt, MoveRowsDelegate reorderDelegate, Func<bool, MoveRowsDelegate> groupDelegateExtractor, MoveRowsDelegate addRowsDelegate)
        {
            int insertRowHandle = hitInfo.RowHandle;
            var grid = GetSourceGrid();

            if (this.GridControl.IsGroupRowHandle(insertRowHandle))
            {
                groupDelegateExtractor(true)(sourceManager, insertRowHandle, HitElement);
                return;
            }
            if (IsSortedButNotGrouped(grid) || hitInfo.HitTest == TableViewHitTest.DataArea)
            {
                if (sourceManager.DraggingRows.Count > 0 && GetDataAreaElement(HitElement) != null/* && !ReferenceEquals(sourceManager, this)*/)
                    addRowsDelegate(sourceManager, insertRowHandle, HitElement);
                else
                    ClearDragInfo(sourceManager);

                return;
            }
            if (insertRowHandle == GridControl.InvalidRowHandle || insertRowHandle == GridControl.AutoFilterRowHandle || insertRowHandle == GridControl.NewItemRowHandle)
            {
                ClearDragInfo(sourceManager);
                return;
            }
            if (this.GridControl.GroupCount > 0)
            {
                int groupRowHandle = this.GridControl.GetParentRowHandle(insertRowHandle);
                if (ShouldReorderGroup(grid))
                {
                    if (!IsSameGroup(sourceManager, GetGroupInfos(groupRowHandle), HitElement))
                        groupDelegateExtractor(false)(sourceManager, groupRowHandle, HitElement);
                    reorderDelegate(sourceManager, insertRowHandle, HitElement);
                }
                else
                    groupDelegateExtractor(true)(sourceManager, groupRowHandle, HitElement);
            }
            else
            {
                reorderDelegate(sourceManager, insertRowHandle, HitElement);
            }
        }

        public delegate void MoveRowsDelegate(DragDropManagerBase sourceManager, int targetRowHandle, DependencyObject hitElement);
    }
}
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