DataGrid fixes for:

- Issue #2977 - Current cell not restored after row deletion, causing crash
- Crash when undoing combobox column change
- Inability to click combobox text to open dropdown

Microsoft.Toolkit.Uwp.UI.Controls.DataGrid/DataGrid/DataGrid.cs

@@ -5740,20 +5740,25 @@ namespace Microsoft.Toolkit.Uwp.UI.Controls
                         break;
                     }
 
-                    // Walk up the visual tree.  If we hit the root, try using the framework element's
+                    // Walk up the visual tree. Try using the framework element's
                     // parent.  We do this because Popups behave differently with respect to the visual tree,
                     // and it could have a parent even if the VisualTreeHelper doesn't find it.
-                    DependencyObject parent = VisualTreeHelper.GetParent(focusedDependencyObject);
-                    if (parent == null)
+                    DependencyObject parent = null;
+                    FrameworkElement element = focusedDependencyObject as FrameworkElement;
+                    if (element == null)
                     {
-                        FrameworkElement element = focusedDependencyObject as FrameworkElement;
-                        if (element != null)
+                        parent = VisualTreeHelper.GetParent(focusedDependencyObject);
+                    }
+                    else
+                    {
+                        parent = element.Parent;
+                        if (parent == null)
                         {
-                            parent = element.Parent;
-                            if (parent != null)
-                            {
-                                dataGridWillReceiveRoutedEvent = false;
-                            }
+                            parent = VisualTreeHelper.GetParent(focusedDependencyObject);
+                        }
+                        else
+                        {
+                            dataGridWillReceiveRoutedEvent = false;
                         }
                     }
 

Microsoft.Toolkit.Uwp.UI.Controls.DataGrid/DataGrid/DataGridComboBoxColumn.cs

@@ -355,16 +355,29 @@ namespace Microsoft.Toolkit.Uwp.UI.Controls
         protected override void CancelCellEdit(FrameworkElement editingElement, object uneditedValue)
         {
             var comboBox = editingElement as ComboBox;
-            if (comboBox != null && uneditedValue != null)
-            {
-                var value = uneditedValue.GetType().GetProperty(Binding.Path.Path).GetValue(uneditedValue);
-                var selection = ItemsSource?.Cast<object>().FirstOrDefault(x => x.GetType().GetProperty(Binding.Path.Path).GetValue(x).Equals(value));
 
-                comboBox.SelectedItem = selection;
-            }
-            else if (comboBox != null)
+            if (comboBox != null)
             {
-                comboBox.SelectedItem = null;
+                if (uneditedValue != null)
+                {
+                    var property = uneditedValue.GetType().GetProperty(Binding.Path.Path);
+
+                    if (property == null)
+                    {
+                        comboBox.SelectedItem = uneditedValue;
+                    }
+                    else
+                    {
+                        var value = property.GetValue(uneditedValue);
+                        var selection = ItemsSource?.Cast<object>().FirstOrDefault(x => x.GetType().GetProperty(Binding.Path.Path).GetValue(x).Equals(value));
+
+                        comboBox.SelectedItem = selection;
+                    }
+                }
+                else
+                {
+                    comboBox.SelectedItem = null;
+                }
             }
         }
 

Microsoft.Toolkit.Uwp.UI.Controls.DataGrid/DataGrid/DataGridRows.cs

@@ -2706,6 +2706,23 @@ namespace Microsoft.Toolkit.Uwp.UI.Controls
             CorrectSlotsAfterDeletion(slot, isRow);
 
             OnRemovedElement(slot, item, isRow);
+
+            // Synchronize CurrentCellCoordinates, CurrentColumn, CurrentColumnIndex, CurrentItem
+            // and CurrentSlot with the currently edited cell, since OnRemovingElement called
+            // SetCurrentCellCore(-1, -1) to temporarily reset the current cell.
+            if (_temporarilyResetCurrentCell &&
+                _editingColumnIndex != -1 &&
+                _previousCurrentItem != null &&
+                this.EditingRow != null &&
+                this.EditingRow.Slot != -1)
+            {
+                ProcessSelectionAndCurrency(
+                    columnIndex: _editingColumnIndex,
+                    item: _previousCurrentItem,
+                    backupSlot: this.EditingRow.Slot,
+                    action: DataGridSelectionAction.None,
+                    scrollIntoView: false);
+            }
         }
 
         private void RemoveNonDisplayedRows(int newFirstDisplayedSlot, int newLastDisplayedSlot)