使用 IEnumerable 集合在 Item 模板内绑定 ComboBox

Question

我有一个类MovieSystem，它继承自AvailableMovies集合。

public class MovieSystem  : IEnumerable<AvailableMovies >, IEnumerable
{
    public AvailableMovies this[int i] { get; }
    public AvailableMovies this[TheatreLocation location] { get; }
    public AvailableMovies [] ReleasedMovies { get; }
 }

TheatreLocation 是一个枚举，其值类似于

public enum TheatreLocation 
{
        Citycentre = 0,
        CityNorth = 1,
        CitySouth = 2,
        CityEast = 3,
        CityWest = 4,
}

可用电影集合，具有以下属性

public class AvailableMovies 
{
        public AvailableMovies ();
        public int Index { get; }
        public TheatreLocation Location { get; set; }
        public string TheatreID { get; set; }
        public double Ticketprice{ get; }
}

我的 Xaml 代码如下所示

<ItemsControl ItemsSource="{Binding MovieSystem  }">            
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                            <ComboBox 
                                      ItemsSource="{Binding Path= ""What should I bind here? ""}"
                                      DisplayMemberPath="{Binding Path = ???}"
                                      SelectedIndex="{Binding Path =Location , Mode=TwoWay, Converter={StaticResource MovieSystemLocationConverter}}">
                            </ComboBox>
                            <ComboBox
                                      ItemsSource="{Binding Path = ???}"
                                      SelectedIndex="{Binding Path=TheatreID , Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                                      DisplayMemberPath="{Binding Path= ??}">
                            </ComboBox>
                            <TextBox Grid.Column="3"
                                     Text="{Binding Path= Ticketprice, Mode =TwoWay,StringFormat=F3, NotifyOnValidationError=True}"/>
                                    
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
</ItemsControl>

我有一个视图模型，xaml 数据上下文设置为此视图模型。

internal class MovieSystemPanelViewModel
{
        ///tried this collection but not worked.
        public ObservableCollection<LocationViewModel> Locations { get; } = new ObservableCollection<LocationViewModel>();
   
        public MovieSystem MovieSystem { get; }
              
        public MovieSystemPanelViewModel() {}
}

现在我的问题是 ComboBox 应该显示剧院 ID，而位置由于绑定问题而未显示。如果尝试在 ComboBox itemsource 内绑定 Locations 可观察集合，则不允许，在 items 模板内，只有 AvailableMovies 属性处于可绑定状态。 Ticketprice 已正确绑定并显示。

Answer 1

这里的问题是，由于您将 Items.Control 与集合绑定，因此该 Items.Control 的子元素将只能访问该集合的属性。因此，如果您想使用另一个集合，则需要使用相对源来获取datacontext级别的访问权限。由于它是一个要正确显示的 enum ，因此您需要使用扩展方法显示字典值，并在 ComboBox 内使用另一个 Itemtemplate 来获取正确的显示。

internal class MovieSystemPanelViewModel
{
        ///Use  dictionary instead of observable collection
        public Dictionary<TheatreLocation , string> Locations { get; } = new Dictionary<TheatreLocation , string>();
   
        public MovieSystem MovieSystem { get; };
              
        public MovieSystemPanelViewModel() 
        {
            // Fill up data in dictionary
            foreach (Enum item in Enum.GetValues(typeof(TheatreLocation)))
            {
                Locations.Add((TheatreLocation)item, ((TheatreLocation)item).GetDisplayName());
            }
        }
}

在项目某处写一个Extension方法，用于根据需求显示成员。

public static string GetDisplayName(this TheatreLocation location)
{
            switch (location)
            {
                case TheatreLocation.CityCentre:
                    return "Center city location";

                case TheatreLocation.CityNorth :
                    return "Northern city location";

                case TheatreLocation.CitySouth :
                    return "Southern city location";

                case TheatreLocation.CityEast :
                    return "Eastern city location";

                case CameraLocation.CityWest :
                    return "Western city location";

                 default:
                    return "Unknown";
            }
}

现在将 xaml 与这些属性和方法绑定。

<ComboBox 
         ItemsSource="{Binding Path= DataContext.Locations, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}"
          SelectedIndex="{Binding Path =Location , Mode=TwoWay, Converter={StaticResource MovieSystemLocationConverter}}">
            <ComboBox.ItemTemplate>
                  <DataTemplate>
                             <TextBlock Text="{Binding Path=Value}" />
                   </DataTemplate>
              </ComboBox.ItemTemplate>
</ComboBox>