WPF、MVVM、工作单元

Question

我正在使用 MVVM 构建 WPF 应用程序，但在开发过程中遇到了问题。如何使 ViewModel 类和 xaml 文件一起工作，即，如果 ViewModel 类采用 IUnitOfWork 参数，则将该类作为 DataContext 传递？

ViewModel 类

[INotifyPropertyChanged]
public partial class TeacherViewModel
{
    [ObservableProperty]
    private ObservableCollection<Teacher> _teachers;
    [ObservableProperty]
    private Teacher _selectedTeacher;
    [ObservableProperty]
    private string _firstName;
    [ObservableProperty]
    private string _lastName;
    private IUnitOfWork _unitOfWork;
    private ITeacherRepository _teacherRepository;

    public TeacherViewModel(IUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork ?? throw new ArgumentNullException(nameof(unitOfWork));
        _teacherRepository = _unitOfWork.TeacherRepository;
        _teachers = new ObservableCollection<Teacher>(_teacherRepository.GetAll());
    }
}

XAML 文件

<Page x:Class="ProgrammingCourses.Views.Pages.EditTeacher"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:vm="clr-namespace:ProgrammingCourses.ViewModels"
      mc:Ignorable="d" 
      d:DesignHeight="400" 
      d:DesignWidth="600"
      Title="EditTeacher">
    <Page.DataContext>
        <vm:TeacherViewModel/> <!-- the type "TeacherViewModel" does not include any accessible constructors -->
    </Page.DataContext>
...

Answer 1

您可以使用 C# 并从构造函数实例化数据上下文，或使用 XAML 并使用

ObjectDataProvider

:

创建数据上下文实例

C#

EditTeacher.xaml.cs

partial class EditTeacher : Page
{
  public EditTeacher()
  {
    IUnitOfWork unitOfWork = new UnitOfWorkImpl();
    var viewModel = new EditTeacherViewModel(unitOfWork);
    this.DataContext = viewModel;

    InitializeComponent();
  }
}

XAML

应用程序.xaml

<Application>
  <Application.Resources>
    <ObjectDataProvider x:Key="EditTeacherViewModelProvider"
                        ObjectType="{x:Type local:EditTeacherViewModel}">
      <ObjectDataProvider.ConstructorParameters>
        <local:UnitOfWorkImpl />
      </ObjectDataProvider.ConstructorParameters>
    </ObjectDataProvider>
  </Application.Resources>
</Application>

编辑教师.xaml

<Page DataContext="{Binding Source={StaticResource EditTeacherViewModelProvider}}">

</Page>

如果您使用依赖注入，则必须采取稍微不同的路线。您将使用组合来组合主视图模型类。然后让 IoC 容器导出这个主视图模型。然后视觉根的子元素（或这些元素的

DataContext

）可以引用所需的视图模型类vbia主视图模型。