使用LINQ时，DataGrid中的排序和滚动非常慢

Question

在使用LINQ的DataGrid中，排序和滚动非常慢。将它与存储过程的结果绑定时，它的效果很好。

只有200条记录。这是为什么？

我尝试使用以下属性来DataGrid，但没有运气：

EnableRowVirtualization="True"
EnableColumnVirtualization="True"
ScrollViewer.CanContentScroll="True" 

这是简单的LINQ代码，它返回带有客户对象的客户列表：

public List<Customer> GetLinkedCustomer()
{
     using (MYModel context = new MYModel())
     {
         return context.Customers.Where(x => x.CustLong1 != null).OrderBy(customer => customer.LastName).ToList();
     }
}

XAML代码：

<Grid Margin="5,5,5,5" Height="Auto" Width="700">
        <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />

       </Grid.RowDefinitions>
    <DataGrid Grid.Row="0" Name="dgLinkedCustomers"  Height="250" CanUserAddRows="False" AutoGenerateColumns="False" CanUserSortColumns="True" IsReadOnly ="True" SelectionMode="Single">
        <DataGrid.Columns>
            <DataGridTextColumn IsReadOnly="True"  Binding="{Binding FirstName , IsAsync=True}" Header="{x:Static res:Strings.Common_FirstName}" Width="150"/>
            <DataGridTextColumn IsReadOnly="True"  Binding="{Binding LastName , IsAsync=True}" Header="{x:Static res:Strings.Common_LastName}" Width="175"/>
            <DataGridTextColumn IsReadOnly="True"  Binding="{Binding ShopName, IsAsync=True}" Header="{x:Static res:Strings.ShopName}" Width="215"/>
            <DataGridTextColumn IsReadOnly="True"  Binding="{Binding CustLong1 , IsAsync=True}" Header="{x:Static res:Strings.AccountNumber}" Width="*"/>
        </DataGrid.Columns>
    </DataGrid>
    <StackPanel Grid.Row="1" Orientation="Vertical" Margin="0,0,0,5" HorizontalAlignment="Right">

        <StackPanel Orientation="Horizontal" VerticalAlignment="Center">
            <Button Name="Close" Margin="0,0,10,0" Width="100">
                <AccessText Text="{x:Static res:Strings.BtnText_Close}" />
            </Button>
            <Button Name="Unlink" Margin="0,0,10,0" Width="100" Click="Unlink_OnClick">
                <AccessText>Unlink</AccessText>
            </Button>
        </StackPanel>

    </StackPanel>
</Grid>