Binding errors coming from under hood

Question

Trying to use grouping in DataGrid and for no reasons getting those binding errors (they are not belong to my code, nor I see a way to deal with them):

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.DataGrid', AncestorLevel='1''. BindingExpression:Path=AreRowDetailsFrozen; DataItem=null; target element is 'DataGridDetailsPresenter' (Name=''); target property is 'SelectiveScrollingOrientation' (type 'SelectiveScrollingOrientation')

and

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.DataGrid', AncestorLevel='1''. BindingExpression:Path=HeadersVisibility; DataItem=null; target element is 'DataGridRowHeader' (Name=''); target property is 'Visibility' (type 'Visibility')

They appears for each row in DataGrid. This bugs me alot!

To reproduce the problem I made a small project

public class MyItem
{
    public string A { get; set; }
}

public class ViewModel
{
    public List<MyItem> List { get; set; }

    public ViewModel()
    {
        List = new List<MyItem>(new[] { new MyItem() });
    }
}

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new ViewModel();
    }
}

xaml

<DataGrid ItemsSource="{Binding List}" AutoGenerateColumns="False">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding A}" Header="A"/>
    </DataGrid.Columns>
    <DataGrid.GroupStyle>
        <GroupStyle>
            <GroupStyle.ContainerStyle>
                <Style TargetType="GroupItem">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="GroupItem">
                                <!-- anything or nothing here -->
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </GroupStyle.ContainerStyle>
        </GroupStyle>
    </DataGrid.GroupStyle>
</DataGrid>

Some observations:

without DataGrid.GroupStyle there are no errors;
with AutoGenerateColumns = true there are no errors;
without binding (setting DataGrid.ItemsSource directly) there are no errors.

Only combination of opposite to those 3 conditions will start spamming Output window with above messages.

What should I do? I can't ignore errors, nor I see a way to fix them.

Googling around wasn't really helpful, to example, this case was called a bug, I tried to apply its workarounds, but none works for me.

P.S.: discovering such bugs at first attempt to use DataGrid is very demotivating.

Trying to deal with second error.

<DataGrid.RowHeaderStyle>
    <Style TargetType="DataGridRowHeader">
        <Setter Property="Visibility" Value="Collapsed"/>
        <Setter Property="Template" Value="{x:Null}"/>
    </Style>
</DataGrid.RowHeaderStyle>

But error still

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.DataGrid', AncestorLevel='1''. BindingExpression:Path=HeadersVisibility; DataItem=null; target element is 'DataGridRowHeader' (Name=''); target property is 'Visibility' (type 'Visibility')

Sinatr Sinatr · Accepted Answer · 2014-10-31T09:19:32

Was playing with control templates and after changing one for DataGridRow errors are gone!

<DataGrid.RowStyle>
    <Style TargetType="DataGridRow">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="DataGridRow">
                    <Border BorderThickness="{TemplateBinding Border.BorderThickness}" BorderBrush="{TemplateBinding Border.BorderBrush}" Background="{TemplateBinding Panel.Background}" Name="DGR_Border" SnapsToDevicePixels="True">
                        <SelectiveScrollingGrid>
                            <DataGridCellsPresenter ItemsPanel="{TemplateBinding ItemsControl.ItemsPanel}" SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}"/>
                        </SelectiveScrollingGrid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</DataGrid.RowStyle>

I removed DataGridDetailsPresenter and DataGridRowHeader from default template, because I will not use them.

I got one more error

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.DataGrid', AncestorLevel='1''. BindingExpression:Path=NewItemMargin; DataItem=null; target element is 'DataGridRow' (Name=''); target property is 'Margin' (type 'Thickness')

which I fix by adding Margin setter into DataGrid.RowStyle

<Setter Property="Margin" Value="0"/>

It seems all of such errors can be fixed by re-factoring default templates.

Binding errors coming from under hood

2 Answers