通过按钮命令填充数据网格

Question

上下文在资源部分引用我的ViewModel

<DataGrid DataContext="{StaticResource TheContext}"
          ItemsSource="{Binding Path=Cars}">

这是我的viewModel.cs

public CarsSearchResultsViewModel()
{
     ButtonCommand = new DelegateCommand(x => GetCars());
}
public void GetCars()
{
     List<Car> cars = new List<Car>();
     cars.Add(new Car() { Make = "Chevy", Model = "Silverado" });
     cars.Add(new Car() { Make = "Honda", Model = "Accord" });
     cars.Add(new Car() { Make = "Mitsubishi", Model = "Galant" });
     Cars = new ObservableCollection<Car>(cars);
}
private ObservableCollection<Car> _cars;
public ObservableCollection<Car> Cars
{
     get { return _cars; }
     private set
     {
         if (_cars == value) return;
         _cars = value;
     }
}

我试过添加OnPropertyChanged("Cars")，我试过在添加列表之前添加People = null，我试过将UpdateSourceTrigger=PropertyChanged添加到ItemsSource，在使用ObservableCollection之前我试过使用IViewCollection。

我不试图更新或删除从一个集合，只是填充一个按钮点击网格。如果我在没有命令的构造函数中运行GetCars()，它可以正常工作。

Answer 1

你的ViewModel需要实现INotifyPropertyChanges接口，并在ObservableCollection的setter中调用OnpropertyChanged，这样当你恢复UI时会得到通知，所以你的Cars属性应该看起来像这样:

private ObservableCollection<Car> _cars ;
    public ObservableCollection<Car> Cars
    {
        get
        {
            return _cars;
        }
        set
        {
            if (_cars == value)
            {
                return;
            }
            _cars = value;
            OnPropertyChanged();
        }
    }

Cars集合需要在 Context类中定义，因为它是您的Context，最后一个需要实现前面提到的接口:

public  class TheContext:INotifyPropertyChanged
{

    //Cars property and your code ..
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
}