Question

I have a DataGrid (the official one) with SelectionUnit="Cell". When the user selects a cell, I’d like to show the row details for the corresponding row. This is apparently not the default behavior, and I can’t seem to figure out how to accomplish this.

Here’s my XAML:

<UserControl x:Class="View.Test"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="../AppResources.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </UserControl.Resources>
    <Grid>
        <DataGrid AutoGenerateColumns="False" 
                ItemsSource="{Binding Path=Fields}" 
                BorderBrush="Transparent" 
                HeadersVisibility="Column"
                SelectionMode="Single"
                SelectionUnit="Cell"
                CanUserAddRows="False"
                CanUserDeleteRows="False"
                CanUserSortColumns="False"
                IsTextSearchEnabled="True"
                x:Name="EntryGrid"
                >
            <DataGrid.Columns>
                <DataGridTextColumn Header="Name" Binding="{Binding Path=Name}" Width="Auto" IsReadOnly="True"/>
                <DataGridTemplateColumn Header="Value" Width="Auto" x:Name="valueColumn" MinWidth="60" MaxWidth="90">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding Path=DisplayValue}" TextTrimming="CharacterEllipsis" ToolTip="{Binding Path=Text, RelativeSource={RelativeSource Self}}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                    <DataGridTemplateColumn.CellEditingTemplate>
                        <DataTemplate>
                            <DockPanel>
                                <ComboBox TabIndex="1" HorizontalAlignment="Stretch" VerticalAlignment="Center" SelectedValue="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}" SelectedValuePath="Value" ItemsSource="{Binding Path=FieldOptions}" Visibility="{Binding Path=FieldOptions, Converter={StaticResource EmptyCollectionIsInvisibleConverter}}" />
                                <TextBox TabIndex="2" Text="{Binding Value, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Center" HorizontalAlignment="Stretch" Visibility="{Binding Path=FieldOptions, Converter={StaticResource NonEmptyCollectionIsInvisibleConverter}}"/>
                            </DockPanel>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>
                </DataGridTemplateColumn>
                <DataGridTemplateColumn Header="Description" IsReadOnly="True" Width="*" >
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding Description}" TextWrapping="Wrap" />
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
            <DataGrid.RowDetailsTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Path=Help}" />
                </DataTemplate>
            </DataGrid.RowDetailsTemplate>
        </DataGrid>
    </Grid>
</UserControl>

Answer 1

You can set the SelectionUnit to FullRow

SelectionUnit="FullRow"

or you can handle the selection event and set the visibility on event handling.

    private void EntryGrid_SelectedCellsChanged(object sender, SelectedCellsChangedEventArgs e)
    {
        foreach (var cell in e.AddedCells)
        ((DataGridRow)EntryGrid.ItemContainerGenerator.ContainerFromItem(cell.Item)).DetailsVisibility = System.Windows.Visibility.Visible;
        foreach (var cell in e.RemovedCells)
            ((DataGridRow)EntryGrid.ItemContainerGenerator.ContainerFromItem(cell.Item)).DetailsVisibility = System.Windows.Visibility.Collapsed;
    }

Insert disparaging remarks about the WPF DataGrid here.