<DataGrid.RowStyle>

    <Style TargetType="DataGridRow">

        <Setter Property="ToolTip">

            <Setter.Value>

                <TextBlock Text="{Binding ToolTipText}" />

            </Setter.Value>

        </Setter>

    </Style>

</DataGrid.RowStyle>

<DataGrid Name="grid" AutoGenerateColumns="False">

    <DataGrid.RowDetailsTemplate>

        <DataTemplate>

            <TextBlock Background="Orange" Text="{Binding MoreInfo}" TextWrapping="Wrap"

                       HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />

        </DataTemplate>

    </DataGrid.RowDetailsTemplate>

    <DataGrid.Columns>

        <DataGridTextColumn Header="ID" Binding="{Binding ID}" />

        <DataGridTextColumn Header="ID" Binding="{Binding Name}" />

        <DataGridTextColumn Header="ID" Binding="{Binding Surname}" />

    </DataGrid.Columns>

</DataGrid>