得到SelectedItem的ComboBox界多点列表

Question

我有一个多列List绑定到一个ComboBox。

它将列表列Name显示为ItemSource。

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问题

SelectedItem确实返回了Name。

使用MessageBox.Show(vm.cboVideoQuality_SelectedItem);，string显示为MyProgram.ViewModel+VideoQuality而不是High。

我尝试使用以下方法过滤Name：

vm.cboVideoQuality_SelectedItem.FirstOrDefault(s => s.Name);

但是它给出了错误的'char' does not contain definition for Name。

XAML

绑定Item Source和Selected Item。

<ComboBox x:Name="cboVideoQuality" 

          ItemsSource="{Binding cboVideoQuality_Items, Mode=TwoWay}"
          DisplayMemberPath="Name"

          SelectedItem="{Binding cboVideoQuality_SelectedItem, Mode=TwoWay}"
          SelectedValuePath="Name"

          HorizontalAlignment="Left" 
          VerticalAlignment="Top" 
          Margin="0,0,0,0" 
          Width="100" />

ViewModel

// Item Source
//
public class VideoQuality
{
    public string Name { get; set; }
    public string Bitrate { get; set; }
}

public List<VideoQuality> _cboVideoQuality_Items = new List<VideoQuality>()
{
     new ViewModel.VideoQuality() { Name = "High",   Bitrate = "5000K" },
     new ViewModel.VideoQuality() { Name = "Medium", Bitrate = "2500K" },
     new ViewModel.VideoQuality() { Name = "Low",    Bitrate = "500K" },
};

public List<VideoQuality> cboVideoQuality_Items
{
    get { return _cboVideoQuality_Items; }
    set
    {
        _cboVideoQuality_Items = value;
        OnPropertyChanged("cboVideoQuality_Items");
    }
}


// Selected Item
//
public string _cboVideoQuality_SelectedItem { get; set; }
public string cboVideoQuality_SelectedItem
{
    get { return _cboVideoQuality_SelectedItem; }
    set
    {
        if (_cboVideoQuality_SelectedItem == value)
        {
            return;
        }

        _cboVideoQuality_SelectedItem = value;
        OnPropertyChanged("cboVideoQuality_SelectedItem");
    }
}

C#

我不能检查selected = "High"是否是SelectedItem，因为SelectedItem不等于Name。

它等于MyProgram.ViewModel+VideoQuality。

ViewModel vm = mainwindow.DataContext as ViewModel;

string selected = vm.cboVideoQuality_SelectedItem;

if (selected == "High")
{
    // ...
}

Answer 1

您已经使用了SelectedValuePath，当然也应该使用SelectedValue而不是SelectedItem。

<ComboBox
      ItemsSource="{Binding cboVideoQuality_Items}"
      DisplayMemberPath="Name"
      SelectedValuePath="Name"
      SelectedValue="{Binding cboVideoQuality_SelectedItem}" .../>

请注意，在这两个绑定中，Mode=TwoWay都是多余的。默认情况下，ItemsSource绑定永远不是双向绑定，而SelectedValue绑定是双向绑定.

我还建议不要在视图模型属性名称中使用绑定目标属性详细信息。cboVideoQuality_SelectedItem应该是SelectedVideoQuality。因此，您也可以将其绑定到SelectedValue属性或ListBox的文本属性，甚至可以绑定到TextBlock的文本属性，而不会造成太多混乱。