Drag and Drop Rows

TreeDataGrid supports row drag/drop with automatic data movement and event hooks.

Enable Auto Drag/Drop

<TreeDataGrid Source="{Binding Source}" AutoDragDropRows="True" />

With this enabled, grid can perform internal move operations when allowed.

Routed Events

RowDragStarted
RowDragOver
RowDrop

Attach in XAML or code-behind.

<TreeDataGrid
    AutoDragDropRows="True"
    RowDragStarted="DragDrop_RowDragStarted"
    RowDragOver="DragDrop_RowDragOver" />

Event Args Essentials

TreeDataGridRowDragStartedEventArgs:

Models: dragged model set
AllowedEffects: set to permit/deny effects

TreeDataGridRowDragEventArgs:

TargetRow: row being hovered/dropped
Position: None, Before, After, Inside
Inner: underlying DragEventArgs

Common Event Logic

Example from sample pattern:

private void DragDrop_RowDragStarted(object? sender, TreeDataGridRowDragStartedEventArgs e)
{
    foreach (DragDropItem i in e.Models)
    {
        if (!i.AllowDrag)
            e.AllowedEffects = DragDropEffects.None;
    }
}

private void DragDrop_RowDragOver(object? sender, TreeDataGridRowDragEventArgs e)
{
    if (e.Position == TreeDataGridRowDropPosition.Inside &&
        e.TargetRow?.Model is DragDropItem i &&
        !i.AllowDrop)
        e.Inner.DragEffects = DragDropEffects.None;
}

Source-Side Move Constraints

Automatic move operation is blocked when:

source is sorted
drag effect is not Move
source collections are not mutable IList<T>

Flat source supports Before / After.

Hierarchical source supports Before / After / Inside.

Drop Position Semantics

Before: insert before target row
After: insert after target row
Inside: insert as child of target row (hierarchical only)

UX Behavior

Grid shows drag adorner and supports auto-scroll near edges while dragging.

Troubleshooting

Feature behavior differs from expectations Cause: one or more options in this scenario are configured differently (source type, column options, sort/selection/edit state). Fix: compare your setup with the snippet in this article and verify runtime values on Source, Columns, and Selection.
Data changes are not visible in UI Cause: model or collection notifications are missing, or a replaced collection/source is not re-bound. Fix: ensure INotifyPropertyChanged/INotifyCollectionChanged flow is active and reassign Source after replacing underlying collections.