How to do validation in DataGrid?

Question

WPF

<Window x:Class="WpfApplicationTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <DataGrid AutoGenerateColumns="False" ItemsSource="{Binding Users}">
            <DataGrid.Resources>
                <Style x:Key="ErrorStyle" TargetType="{x:Type TextBox}">
                    <Setter Property="Padding" Value="-2" />
                    <Style.Triggers>
                        <Trigger Property="Validation.HasError" Value="True">
                            <Setter Property="Background" Value="Red" />
                                <Setter Property="ToolTip"
                                    Value="{Binding RelativeSource={RelativeSource Self},
            Path=(Validation.Errors)[0].ErrorContent}" />
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </DataGrid.Resources>
            <DataGrid.Columns>
                <DataGridTextColumn Header="Имя" Binding="{Binding Path=FirstName,ValidatesOnExceptions=True}"
                                    EditingElementStyle="{StaticResource ErrorStyle}" />
                <DataGridTextColumn Header="Фамилия" Binding="{Binding Path=LastName, ValidatesOnExceptions=True}" EditingElementStyle="{StaticResource ErrorStyle}"  />
                <DataGridTextColumn Header="Отчество" Binding="{Binding Path=MiddleName,ValidatesOnExceptions=True}" EditingElementStyle="{StaticResource ErrorStyle}"  />
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

In this example, if there is an error in the data object, the cell should be highlighted with a red frame and a tooltip with an error message will appear. It does not work, I no longer know where to poke, as the small red "!" Icon showed, and it shows. Poke your nose, please, what's wrong here.

Answer 1

Do fields have validation attributes in the model?