Question

找不到我的项目ViewModel元素。我正在尝试在WPF Usercontrol中实现ViewModel。但是，绑定工作不正常，似乎没有数据。我正在尝试创建一个ViewModel进行交互，将通用字符串数组放入其中，以及各种其他数据位。

MainWindow.xaml - （用户控制声明）

<panels:FilterLister Grid.Column="0" x:Name="filter1FilterLister" />

MainWindows.cs - （在构造函数中，调用usercontrol

filter1FilterLister.Initialise(typeof(Genre));

FilterListViewModel.cs

public class FilterListViewModel
{
    MyEntities context = new MyEntities();
    ObservableCollection<string> entries = new ObservableCollection<string>();

    public Type SelectedType;
    private string p_TypeName;
    public string TypeName
    {
        get { return p_TypeName; }
        set { 
            //p_TypeName = value; 
            p_TypeName = SelectedType.Name.ToString();
        }
    }

    public FilterListViewModel() { }

    public FilterListViewModel(Type selectedType)
    {
        if (selectedType == typeof(Artist))
        {
            returnedArray = Artist.ReturnArtistNames(context);
        }

        // put together ObservableCollection
        foreach (var str in returnedArray)
        {
            entries.Add(str);
        }

        SelectedType = selectedType;
    }
}

FilterLister.xaml

<Label Name="labelToBind" Content="{Binding TypeName}" Grid.Row="0" />

FilterLister.cs

public partial class FilterLister : UserControl
{
    FilterListViewModel filterListViewModel;
    private MyEntities context;

    public FilterLister()
    {
        InitializeComponent();
        context = new MyEntities();
    }

    public void Initialise(Type objectType)
    {
        filterListViewModel = new FilterListViewModel(objectType);
        this.DataContext = filterListViewModel;
    }
}

Answer 1

您错过了在ViewModel中实现INotifyPropertyChanged接口，binded属性需要将“刷新消息”发送到UI。

这是界面，以及如何实现这个： http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx

    public class FilterListViewModel : INotifyPropertyChanged
{
MyEntities context = new MyEntities();
ObservableCollection<string> entries = new ObservableCollection<string>();

public Type SelectedType;
private string p_TypeName;
public string TypeName
{
    get { return p_TypeName; }
    set { 
        //p_TypeName = value; 
        p_TypeName = SelectedType.Name.ToString();
  NotifyPropertyChanged();

    }
}

public FilterListViewModel() { }

public FilterListViewModel(Type selectedType)
{
    if (selectedType == typeof(Artist))
    {
        returnedArray = Artist.ReturnArtistNames(context);
    }

    // put together ObservableCollection
    foreach (var str in returnedArray)
    {
        entries.Add(str);
    }

    SelectedType = selectedType;
}

private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
 }

Answer 2

根据您的代码，TypeName为null，因此您在Label上看不到任何内容。从您的代码中，我认为您想描述如下：

public string TypeName
{
   get{ return SelectedType.Name.ToString();}
}

正如deryck建议的那样，您应该添加INotifyPropertyChanged接口以进行通知，但它不应该首次影响绑定。如果您认为ViewModel的数据正确但未在UI上填充，则应检查DataContext和Binding。

未找到ViewModel数据

2 个答案: