WPF CheckBox checked event on scrolling thought datagrid

Question

I have a datagrid with a DataGridTemplateColumn containing a CheckBox . I create the column like this:

DataGridTemplateColumn cTemplateColumn = new DataGridTemplateColumn();
cTemplateColumn.Header = "Auswahl";
FrameworkElementFactory cFactory = new FrameworkElementFactory(typeof(CheckBox));
Binding b1 = new Binding("[__intern_cv__]");
//b1.IsAsync = true;
b1.Converter = new StringToBoolConverter(this);
b1.Mode = BindingMode.TwoWay;
b1.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
cFactory.SetValue(CheckBox.IsCheckedProperty, b1);
cFactory.SetValue(CheckBox.HorizontalAlignmentProperty, HorizontalAlignment.Center);
cFactory.AddHandler(CheckBox.CheckedEvent, new RoutedEventHandler(CheckedEvent));
cFactory.AddHandler(CheckBox.UncheckedEvent, new RoutedEventHandler(CheckedEvent));
cFactory.AddHandler(CheckBox.PreviewMouseDownEvent, new MouseButtonEventHandler(checkBoxMouseDown));
DataTemplate cCellTemplate = new DataTemplate();
cCellTemplate.VisualTree = cFactory;
cTemplateColumn.CellTemplate = cCellTemplate;    
Columns.Add(cTemplateColumn);

Now i have the problem, that during scrolling throught the DataGrid , the CheckedEvent is called, with Checked == False .

The vents a subscripted here:

cFactory.AddHandler(CheckBox.CheckedEvent, new RoutedEventHandler(CheckedEvent));
cFactory.AddHandler(CheckBox.UncheckedEvent, new RoutedEventHandler(CheckedEvent));

How can scrolling call the event?

maybe someone has an idea, thank you!

Answer 1

By default the DataGrid virtualizes its rows. This means that during scrolling old rows are re-used with new data. If the new data has "[__intern_cv__]" set to false, while the previous data had it set to true an Unchecked event will be raised.