Почему не удаётся изменять ширину колонок мышкой в DataGrid?

Страница

<DataGrid x:Name="dateGrid" Width="auto" ScrollViewer.HorizontalScrollBarVisibility="Hidden"  
                          CanUserResizeColumns="True">
                         <DataGrid.Columns>
                             <DataGridTextColumn Header="Номер книги" Width="*" Binding="{Binding Books.NamberBook}"/>
                             <DataGridTextColumn Header="Название книги" Width="*" Binding="{Binding Books.NameBook}"/>
                             <DataGridTextColumn Header="Выдана" Width="*" Binding="{Binding FullName}"/>
                             <DataGridTextColumn Header="Тип" Width="*" Binding="{Binding TypeUsers}"/>
                             <DataGridTextColumn Header="Тип" Width="*" Binding="{Binding TypeUsers}"/>
                             <DataGridTextColumn Header="Дата выдачи" Width="*" Binding="{Binding DateOfISsue, StringFormat={}Дата выдачи: {0:dd.MM.yyyy}}"/>
                             <DataGridTextColumn Header="До" Width="*" Binding="{Binding EndDate, StringFormat={}Окончание выдачи: {0:dd.MM.yyyy}}"/>
                        </DataGrid.Columns>

                 </DataGrid>



<sys:Double x:Key="DataGridRow.Height">33</sys:Double>

    <!--<! - Толщина внешней границы таблицы, как правило, не изменяется->-->
    <Thickness x:Key="DataGrid.BorderThickness" Bottom="1" Left="1" Right="1" Top="1" />
    <!--<! - Толщина заголовка столбца обычно не изменяется->-->
    <Thickness x:Key="ColumnHeader.BorderThickness" Bottom="0" Left="0" Right="1" Top="0" />
    <!--<! - Толщина границы линии, как правило, не изменяется->-->
    <Thickness x:Key="DataGridRow.BorderThickness" Bottom="0" Left="0" Right="0" Top="1" />

    <!--<! - Цвет внешней границы таблицы->-->
    <SolidColorBrush x:Key="DataGrid.BorderBrush" Color="#E9ECF1" />
    <!--<! - Цвет фона заголовка столбца->-->
    <SolidColorBrush x:Key="ColumnHeader.Background" Color="#F6F7FB" />
    <!--<! - Цвет границы заголовка столбца->-->
    <SolidColorBrush x:Key="ColumnHeader.BorderBrush" Color="#E9ECF1" />
    <!--<! - Цвет границы строки->-->
    <SolidColorBrush x:Key="DataGridRow.BorderBrush" Color="#E9ECF1" />
    <!--<! - Цвет фона линии по умолчанию->-->
    <SolidColorBrush x:Key="DataGridRow.Normal.Background" Color="#FFFFFF" />
    <!--<! - Цвет текста строки по умолчанию->-->
    <SolidColorBrush x:Key="DataGridRow.Normal.Foreground" Color="#000000" />
    <!--<! - Цвет фона линии подвески->-->
    <SolidColorBrush x:Key="DataGridRow.MouseOver.Background" Color="#F6F7FB" />
    <!--<! - Цвет плавающей строки текста->-->
    <SolidColorBrush x:Key="DataGridRow.MouseOver.Foreground" Color="#000000" />
    <!-- Цвет фона выделения строки-->
    <SolidColorBrush x:Key="DataGridRow.Selected.Background" Color="#F6F7FB" />
    <!-- Цвет текста выделения строки-->
    <SolidColorBrush x:Key="DataGridRow.Selected.Foreground" Color="#000000" />

    <Style TargetType="DataGrid">
        
        <!--Цвет линии сетки-->
        
        <Setter Property="RowHeaderWidth" Value="0" />
        <Setter Property="BorderThickness" Value="{StaticResource DataGrid.BorderThickness}" />
        <Setter Property="HeadersVisibility" Value="Column" />
        <Setter Property="Background" Value="{StaticResource ColumnHeader.Background}" />
        <Setter Property="BorderBrush" Value="{StaticResource DataGrid.BorderBrush}" />
        <Setter Property="HorizontalGridLinesBrush" Value="#00E9ECF1" />
        <Setter Property="VerticalGridLinesBrush" Value="#00E9ECF1" />
        <Setter Property="UseLayoutRounding" Value="True" />
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="AutoGenerateColumns" Value="False" />
        <Setter Property="CanUserAddRows" Value="False" />
        
        <!--Позволяет двигать колонки местами )-->
        <Setter Property="CanUserReorderColumns" Value="True" />
        
        <!--позволяет менять размер столбцов ????-->
        <Setter Property="CanUserResizeColumns" Value="True" />
        
        <Setter Property="CanUserResizeRows" Value="True" />
        <Setter Property="CanUserSortColumns" Value="True" />
        <Setter Property="GridLinesVisibility" Value="Horizontal" />
        <Setter Property="IsReadOnly" Value="True" />
        <Setter Property="RowHeight" Value="{StaticResource DataGridRow.Height}" />
        <Setter Property="SelectionMode" Value="Single" />
    </Style>

    <!-- Стиль заголовка столбца-->
    <Style TargetType="DataGridColumnHeader">
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="Foreground" Value="#000000" />
        <Setter Property="FontSize" Value="12" />
        
        <Setter Property="FontFamily" Value="Comic Sans MS"/>
        <Setter Property="Cursor" Value="Hand" />
        <Setter Property="Height" Value="28" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="DataGridColumnHeader">
                    <Border x:Name="BackgroundBorder" Width="Auto" Margin="-1,0"                               
                            BorderBrush="{StaticResource ColumnHeader.BorderBrush}"
                            BorderThickness="{StaticResource ColumnHeader.BorderThickness}"
                            SnapsToDevicePixels="True" UseLayoutRounding="True">
                        <ContentPresenter Margin="5,0" HorizontalAlignment="Center" VerticalAlignment="Center" />
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <!--<! - Изменение цвета фона триггера стиля строки должно сначала установить cellStyle, потому что cellStyle переопределит rowStyle style->-->
    <Style TargetType="{x:Type DataGridRow}">
        <Setter Property="Background" Value="{StaticResource DataGridRow.Normal.Background}" />
        <Setter Property="Foreground" Value="{StaticResource DataGridRow.MouseOver.Foreground}" />
        <Setter Property="SnapsToDevicePixels" Value="true" />
        <Setter Property="UseLayoutRounding" Value="True" />
        <Setter Property="Validation.ErrorTemplate" Value="{x:Null}" />
        <Setter Property="BorderThickness" Value="{StaticResource DataGridRow.BorderThickness}" />
        <Setter Property="BorderBrush" Value="{StaticResource DataGridRow.BorderBrush}" />
        <Setter Property="ValidationErrorTemplate">
            <Setter.Value>
                <ControlTemplate>
                    <TextBlock Margin="0,0,0,0" VerticalAlignment="Center" Foreground="Red" Text="!" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DataGridRow}">
                <Border x:Name="DGR_Border" Margin="0,0,0,-1"
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        SnapsToDevicePixels="True" UseLayoutRounding="True">        
                    <SelectiveScrollingGrid>
                            <SelectiveScrollingGrid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition Width="*" />
                            </SelectiveScrollingGrid.ColumnDefinitions>
                            <SelectiveScrollingGrid.RowDefinitions>
                                <RowDefinition Height="*" MinHeight="{StaticResource DataGridRow.Height}" />
                                <RowDefinition Height="Auto" />
                            </SelectiveScrollingGrid.RowDefinitions>
                        <DataGridCellsPresenter Grid.Column="1"
                                                ItemsPanel="{TemplateBinding ItemsPanel}"
                                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                        <DataGridDetailsPresenter Grid.Row="1" Grid.Column="1"
                                            SelectiveScrollingGrid.SelectiveScrollingOrientation="{Binding AreRowDetailsFrozen,
                                            ConverterParameter={x:Static SelectiveScrollingOrientation.Vertical},
                                            Converter={x:Static DataGrid.RowDetailsScrollingConverter},
                                            RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"
                                            Visibility="{TemplateBinding DetailsVisibility}" />
                        <DataGridRowHeader Grid.RowSpan="2" SelectiveScrollingGrid.SelectiveScrollingOrientation="Vertical"
                                            Visibility="{Binding HeadersVisibility,
                                            ConverterParameter={x:Static DataGridHeadersVisibility.Row},
                                            Converter={x:Static DataGrid.HeadersVisibilityConverter},
                                            RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" />
                                                                        </SelectiveScrollingGrid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Foreground" Value="{StaticResource DataGridRow.MouseOver.Foreground}" />
                            <Setter Property="Background" Value="{StaticResource DataGridRow.MouseOver.Background}" />
                        </Trigger>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="Foreground" Value="{StaticResource DataGridRow.Selected.Foreground}" />
                            <Setter Property="Background" Value="{StaticResource DataGridRow.Selected.Background}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <!--<! - Триггер стиля ячейки->-->
    <Style TargetType="DataGridCell">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="DataGridCell">
                    <Border x:Name="Bg" Background="Transparent" UseLayoutRounding="True">
                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Style.Triggers>
            <Trigger Property="IsSelected" Value="True">
                <Setter Property="Background" Value="Transparent" />
                <Setter Property="Foreground" Value="#000000" />
            </Trigger>
        </Style.Triggers>
    </Style>