WPF組合框不會更新當前選定的項目

Question

我遇到了與我的組合框有關的問題。不知怎的，它可能會與自己不同步。例如，在我更換BlockSequenceFields後，只有下拉文本被修改。在下面，字段1已更新，但您可以看到它不反映在當前選定的項目中。

我IsSynchronizedWithCurrentItem =真應該讓當前選定的項目像預期的那樣，但它似乎並沒有工作。我讀過很多目前的項目不匹配的stackoverflow帖子，但他們只是將IsSynchronizedWithCurrentItem設置爲true，它修復了他們的問題。

任何人都可以解釋爲什麼這不適合我嗎？

<ComboBox x:Name="SequenceFieldComboBox" 
       SelectedItem="{Binding BlockSequenceFieldIndex, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
       ItemsSource="{Binding BlockSequenceFields, UpdateSourceTrigger=PropertyChanged}" 
       IsSynchronizedWithCurrentItem="True"> 

     <ComboBox.ItemTemplate> 
      <DataTemplate> 
       <StackPanel Orientation="Horizontal"> 
        <CheckBox 
         IsChecked="{Binding IsCalibrated, Mode=OneWay}" 
         IsEnabled="False"> 
        </CheckBox> 
        <TextBlock 
         Text="{Binding}"> 
        </TextBlock> 
       </StackPanel> 
      </DataTemplate> 
     </ComboBox.ItemTemplate> 
    </ComboBox> 

編輯：張伯倫先生

// ViewModelBase implements INotifyPropertyChanged 
public class BlockFieldViewModel : ViewModelBase 
{ 
    public BlockSequenceField SequenceField { get; set; } 

    public List<BlockSequenceCalibrationItemViewModel> Calibrations => this.SequenceField?.CalibrationList; 

    public bool IsCalibrated => this.Calibrations.TrueForAll(x => x.IsCalibrated == null || x.IsCalibrated == true); 

    public double AmplitudeThreshold => this.Calibrations.Max(x => x.Amplitude); 

    public int FieldNumber { get; set; } 

    public override string ToString() 
    { 
     string ret = string.Format(CultureInfo.CurrentCulture, "Field {0} ", this.FieldNumber); 

     if (Math.Abs(this.AmplitudeThreshold) > .00001) 
     { 
      ret = string.Concat(ret, string.Format(CultureInfo.CurrentCulture, "({0} mA)", this.AmplitudeThreshold)); 
     } 

     return ret; 
    } 
} 

這裏是更大的視圖模型的更多細節，把它MainViewModel.cs。下面是在類相關領域

private ObservableCollection<BlockFieldViewModel> blockSequenceFields; 

    public ObservableCollection<BlockFieldViewModel> BlockSequenceFields 
    { 
     get => this.blockSequenceFields; 
     set 
     { 
      this.blockSequenceFields = value; 
      this.OnPropertyChanged("BlockSequenceFields"); 
     } 
    } 

    private void RefreshFieldList() 
    { 
     // In order for the combo box text to update, we need to reload the items 
     var savedIndex = this.BlockSequenceFieldIndex; // to restore to current field. 
     var fieldList = this.CalibrationViewModel.FieldViewModels; 
     this.BlockSequenceFields = new ObservableCollection<BlockFieldViewModel>(fieldList); 
     this.BlockSequenceFieldIndex = savedIndex; 
    } 

Answer 1

您的問題是，因爲BlockFieldViewModel時引起FieldNumber更新不會引發INPC。您需要至少爲該財產籌集資金。

//Assuming the base class looks like 
public class ViewModelBase : INotifyPropertyChanged 
{ 
    public event PropertyChangedEventHandler PropertyChanged; 

    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) 
    { 
     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); 
    } 
} 


public class BlockFieldViewModel : ViewModelBase 
{ 
    //... 

    public int FieldNumber 
    { 
     get 
     { 
      return _fieldNumber; 
     } 
     set 
     { 
      if(_fieldNumber.Equals(value)) 
       return; 

      OnPropertyChanged(); 
     } 
    } 
    //... 
} 

我不知道是否這將解決您的問題或沒有，由於您使用的ToString（）顯示的名稱。如果你發現以上未在傳遞一個空字符串您OnPropertyChanged方法

public int FieldNumber 
{ 
    get 
    { 
     return _fieldNumber; 
    } 
    set 
    { 
     if(_fieldNumber.Equals(value)) 
      return; 

     //Refresh all properties due to the .ToString() not updating. 
     OnPropertyChanged(""); 
    } 
} 

而且修復它觸發改變整個對象的屬性，如果List<BlockSequenceCalibrationItemViewModel> Calibrations可以添加或刪除，或.Amplitude可能改變你也需要觸發一個名字的刷新。