Fix two problems in cell editing

src/Avalonia.Controls.TreeDataGrid/Models/TreeDataGrid/TextCell.cs

@@ -92,8 +92,8 @@ public void BeginEdit()
         {
             if (!_isEditing && !IsReadOnly)
             {
-                _isEditing = true;
                 _editText = Text;
+                _isEditing = true;
             }
         }
 
@@ -103,6 +103,7 @@ public void CancelEdit()
             {
                 _isEditing = false;
                 _editText = null;
+                RaisePropertyChanged(nameof(Value));
             }
         }
 
@@ -114,6 +115,7 @@ public void EndEdit()
                 _isEditing = false;
                 _editText = null;
                 Text = text;
+                RaisePropertyChanged(nameof(Value));
             }
         }
 

src/Avalonia.Controls.TreeDataGrid/Primitives/TreeDataGridTemplateCell.cs

@@ -104,6 +104,13 @@ protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e
             }
         }
 
+        protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromLogicalTree(e);
+            ContentTemplate = null;
+            EditingTemplate = null;
+        }
+
         protected override void OnDataContextChanged(EventArgs e)
         {
             base.OnDataContextChanged(e);
@@ -121,6 +128,11 @@ protected override void OnDataContextChanged(EventArgs e)
                     ContentTemplate = cell.GetCellTemplate(this);
                     EditingTemplate = cell.GetCellEditingTemplate?.Invoke(this);
                 }
+                else
+                {
+                    ContentTemplate = null;
+                    EditingTemplate = null;
+                }
             }
             else
             {