Showing message 'No data' when WPF DataGrid has no rows

Question

I have a WPF DataGrid in which I want to show a message 'No data' when there are no records within it. So I have done what is explained here in the answer provided by pchajer but when datagrid is show with no data the message is not show. I think I am having problems with AncestorType, I think I am not specifying correctly, but I do not know how to solve this. I do not understand at all how AncestorType works...

Below my code:

<Window x:Class="My.Apps.WPF.Test.wMain"
        xmlns:local="clr-namespace:My.Apps.WPF.Test">

<dg:DataGrid.Style>
    <Style TargetType="dg:DataGrid">
        <Setter Property="RowDetailsVisibilityMode" Value="Collapsed"></Setter>
        <Style.Triggers>
            <DataTrigger Binding="{Binding DataContext.IsRecordExists, 
                                   RelativeSource={RelativeSource Mode=FindAncestor,
                                                                  AncestorType={x:Type local:wMain}}}" Value="false">
                <Setter Property="RowHeight" Value="0"></Setter>
                <Setter Property="RowDetailsVisibilityMode" Value="Visible"></Setter>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</dg:DataGrid.Style>

<!-- Missatge quan no hi ha documents pel procés seleccionat -->
<dg:DataGrid.RowDetailsTemplate>
    <DataTemplate>
        <StackPanel>
            <TextBlock Text="No hi ha documents disponibles pel procés seleccionat" Width="400"></TextBlock>
        </StackPanel>
    </DataTemplate>
</dg:DataGrid.RowDetailsTemplate>

</Window>

Code-behind (XAML.cs):

namespace My.Apps.WPF.Test
{
    public partial class wMain : ViewBaseControl
    {

    }
}

Answer 1

You could bind to the DataGrid's HasItems property and change the template:

<DataGrid.Style>
    <Style TargetType="DataGrid">
        <Style.Triggers>
            <DataTrigger Binding="{Binding HasItems, RelativeSource={RelativeSource Self}}" Value="false">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="DataGrid">
                            <TextBlock Text="No data..." />
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</DataGrid.Style>

There will never be any row details to display if there are no rows in the DataGrid so that approach won't work.

Edit: If you want to display the column headers even when there are no rows, you should include a DataGridColumnHeadersPresenter in the template:

<DataTrigger Binding="{Binding HasItems, RelativeSource={RelativeSource Self}}" Value="false">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="DataGrid">
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="*" />
                    </Grid.RowDefinitions>
                    <DataGridColumnHeadersPresenter x:Name="PART_ColumnHeadersPresenter" Grid.Column="1" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.Column}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                    <TextBlock Text="No data..." Grid.Row="1" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</DataTrigger>