Fix datagrid right click selection

src/Avalonia.Controls.DataGrid/DataGrid.cs

@@ -3002,6 +3002,12 @@ namespace Avalonia.Controls
             }
         }
 
+        //TODO: Ensure right button is checked for
+        internal bool UpdateStateOnMouseRightButtonDown(PointerPressedEventArgs pointerPressedEventArgs, int columnIndex, int slot, bool allowEdit)
+        {
+            KeyboardHelper.GetMetaKeyState(pointerPressedEventArgs.KeyModifiers, out bool ctrl, out bool shift);
+            return UpdateStateOnMouseRightButtonDown(pointerPressedEventArgs, columnIndex, slot, allowEdit, shift, ctrl);
+        }
         //TODO: Ensure left button is checked for
         internal bool UpdateStateOnMouseLeftButtonDown(PointerPressedEventArgs pointerPressedEventArgs, int columnIndex, int slot, bool allowEdit)
         {
@@ -5674,6 +5680,35 @@ namespace Avalonia.Controls
             VerticalScroll?.Invoke(sender, e);
         }
 
+        //TODO: Ensure right button is checked for
+        private bool UpdateStateOnMouseRightButtonDown(PointerPressedEventArgs pointerPressedEventArgs, int columnIndex, int slot, bool allowEdit, bool shift, bool ctrl)
+        {
+            Debug.Assert(slot >= 0);
+
+            if (shift || ctrl)
+            {
+                return true;
+            }
+            if (IsSlotOutOfBounds(slot))
+            {
+                return true;
+            }
+            if (GetRowSelection(slot))
+            {
+                return true;
+            }
+            // Unselect everything except the row that was clicked on
+            try
+            {
+                UpdateSelectionAndCurrency(columnIndex, slot, DataGridSelectionAction.SelectCurrent, scrollIntoView: false);
+            }
+            finally
+            {
+                NoSelectionChangeCount--;
+            }
+            return true;
+        }
+
         //TODO: Ensure left button is checked for
         private bool UpdateStateOnMouseLeftButtonDown(PointerPressedEventArgs pointerPressedEventArgs, int columnIndex, int slot, bool allowEdit, bool shift, bool ctrl)
         {

src/Avalonia.Controls.DataGrid/DataGridCell.cs

@@ -161,21 +161,34 @@ namespace Avalonia.Controls
         private void DataGridCell_PointerPressed(PointerPressedEventArgs e)
         {
             // OwningGrid is null for TopLeftHeaderCell and TopRightHeaderCell because they have no OwningRow
-            if (OwningGrid != null)
+            if (OwningGrid == null)
             {
-                OwningGrid.OnCellPointerPressed(new DataGridCellPointerPressedEventArgs(this, OwningRow, OwningColumn, e));
-                if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+                return;
+            }
+            OwningGrid.OnCellPointerPressed(new DataGridCellPointerPressedEventArgs(this, OwningRow, OwningColumn, e));
+            if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+            {
+                if (!e.Handled)
+                //if (!e.Handled && OwningGrid.IsTabStop)
                 {
-                    if (!e.Handled)
-                    //if (!e.Handled && OwningGrid.IsTabStop)
-                    {
-                        OwningGrid.Focus();
-                    }
-                    if (OwningRow != null)
-                    {
-                        e.Handled = OwningGrid.UpdateStateOnMouseLeftButtonDown(e, ColumnIndex, OwningRow.Slot, !e.Handled);
-                        OwningGrid.UpdatedStateOnMouseLeftButtonDown = true;
-                    }
+                    OwningGrid.Focus();
+                }
+                if (OwningRow != null)
+                {
+                    e.Handled = OwningGrid.UpdateStateOnMouseLeftButtonDown(e, ColumnIndex, OwningRow.Slot, !e.Handled);
+                    OwningGrid.UpdatedStateOnMouseLeftButtonDown = true;
+                }
+            }
+            else if (e.GetCurrentPoint(this).Properties.IsRightButtonPressed)
+            {
+                if (!e.Handled)
+                //if (!e.Handled && OwningGrid.IsTabStop)
+                {
+                    OwningGrid.Focus();
+                }
+                if (OwningRow != null)
+                {
+                    e.Handled = OwningGrid.UpdateStateOnMouseRightButtonDown(e, ColumnIndex, OwningRow.Slot, !e.Handled);
                 }
             }
         }

src/Avalonia.Controls.DataGrid/DataGridRowGroupHeader.cs

@@ -283,7 +283,11 @@ namespace Avalonia.Controls
         //TODO TabStop
         private void DataGridRowGroupHeader_PointerPressed(PointerPressedEventArgs e)
         {
-            if (OwningGrid != null && e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+            if (OwningGrid == null)
+            {
+                return;
+            }
+            if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
             {
                 if (OwningGrid.IsDoubleClickRecordsClickOnCall(this) && !e.Handled)
                 {
@@ -300,6 +304,15 @@ namespace Avalonia.Controls
                     e.Handled = OwningGrid.UpdateStateOnMouseLeftButtonDown(e, OwningGrid.CurrentColumnIndex, RowGroupInfo.Slot, allowEdit: false);
                 }
             }
+            else if (e.GetCurrentPoint(this).Properties.IsRightButtonPressed)
+            {
+                if (!e.Handled)
+                {
+                    OwningGrid.Focus();
+                }
+                e.Handled = OwningGrid.UpdateStateOnMouseRightButtonDown(e, OwningGrid.CurrentColumnIndex, RowGroupInfo.Slot, allowEdit: false);
+            }
+
         }
 
         private void EnsureChildClip(Visual child, double frozenLeftEdge)

src/Avalonia.Controls.DataGrid/DataGridRowHeader.cs

@@ -179,12 +179,12 @@ namespace Avalonia.Controls.Primitives
         //TODO TabStop
         private void DataGridRowHeader_PointerPressed(object sender, PointerPressedEventArgs e)
         {
-            if (!e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+            if (OwningGrid == null)
             {
                 return;
             }
 
-            if (OwningGrid != null)
+            if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
             {
                 if (!e.Handled)
                 //if (!e.Handled && OwningGrid.IsTabStop)
@@ -199,6 +199,19 @@ namespace Avalonia.Controls.Primitives
                     OwningGrid.UpdatedStateOnMouseLeftButtonDown = true;
                 }
             }
+            else if (e.GetCurrentPoint(this).Properties.IsRightButtonPressed)
+            {
+                if (!e.Handled)
+                {
+                    OwningGrid.Focus();
+                }
+                if (OwningRow != null)
+                {
+                    Debug.Assert(sender is DataGridRowHeader);
+                    Debug.Assert(sender == this);
+                    e.Handled = OwningGrid.UpdateStateOnMouseRightButtonDown(e, -1, Slot, false);
+                }
+            }
         } 
 
     }