在XAML中正确设置我的DataContext

Question

I know there are similar questions but I am getting this wrong.

I have:

<Window.Resources>
    <local:StudentList x:Key="StudentList" />
    <local:InverseBooleanConverter x:Key="InverseBooleanConverter" />
    <local:StudentAssignmentToStudentAssignmentLookup x:Key="LookupHistoryConvertor" />
    <CollectionViewSource x:Key="cvsStudentList" Source="{StaticResource StudentList}" Filter="CollectionViewSource_Filter"/>

</Window.Resources>

<Window.DataContext>
    <local:OCLMEditorModel/>
</Window.DataContext>

Futher down in my markup I have a DataGrid :

<DataGrid Name="gridStudents" ItemsSource="{Binding Source={StaticResource cvsStudentList}}"
          Margin="2"
          Height="250"
          AutoGenerateColumns="False" IsReadOnly="True">

But I don't think it is right anymore. My OCLMEditorModel object has a public property called StudentList . If I am understanding this right, at the moment my window is associated with an instance of OCLMEditorModel . But the subsequent DataGrid is associated with a distinct instance of the CollectionViewSource.

So I am getting myself confused. Thanks for guidance.

Answer 1

Trying changing your

<CollectionViewSource x:Key="cvsStudentList" Source="{StaticResource StudentList}" Filter="CollectionViewSource_Filter"/>

to

<CollectionViewSource x:Key="cvsStudentList" Source="{Binding StudentList}" Filter="CollectionViewSource_Filter"/>

You're correct that your DataContext is set initially to an instance of OCLMEditorModel when the window is instantiated. That should mean that your CollectionViewSource resource should be able to grab the StudentList property from the Window's DataContext through a direct binding.

Yes, what you're doing in your xaml is binding your DataGrid's ItemsSource to a distinct instance of the CollectionViewSource. However , you're also binding that CollectionViewSource instance to a distinct instance of a StudentList defined in your Window.Resources ( <local:StudentList x:Key="StudentList" /> ), which I don't think is what you want. The change I suggested above will make your CollectionViewSource bind to the OCLMEditorModel 's StudentList property instead.

Answer 2

您为什么不只绑定到StudentList属性，例如

<DataGrid Name="gridStudents" ItemsSource="{Binding StudentList}" ... />

Answer 3

You directly define your collectionviewsource in the viewmodel and bind collectionviewsource to DataGrid ItemSource

public class StudentViewModel
{
    public ObservableCollection<student> StudentList { get; set; }

    public ICollectionView StudentView { get; set; }

    public StudentViewModel()
    {
        StudentList= new ObservableCollection<student>();
        StudentView = new CollectionView(StudentList);
        StudentView.Filter = Filter;
        StudentView.SortDescriptions.Add(new SortDescription("Name",ListSortDirection.Ascending));
    }

    private bool Filter(object obj)
    {
        return true;
    }
}

<DataGrid Name="gridStudents" ItemsSource="{Binding StudentView}" ... />

Answer 4

You can set DataContext to the following way...

 <Window.Resources>
            <local:OCLMEditorModel x:Key="MyViewModel"/>
        </Window.Resources>
    <DataGrid DataContext="{StaticResource MyViewModel}" Name="gridStudents" ItemsSource="{Binding Source={StaticResource cvsStudentList}}"
              Margin="2"
              Height="250"
              AutoGenerateColumns="False" IsReadOnly="True">