使用 Linq to Entities 绑定到 List<T> 时显示组合框的选定值的问题

Question

我有一个ComboBox，它上面应用了一个ItemTemplate，并使用linq 绑定到实体返回的List。我正在使用 mvvm。它已成功绑定到它，但是当我在运行时从代码中设置它的选定值以显示来自 db 的选定值时，它不会选择它。这里的参考是我的ComboBox xaml。

<DataTemplate x:Key="ManufacturerDataTemplate">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="50"/>     
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>    
        <Image x:Name="imgManufacturer" Width="25" Height="25"
               Source="{Binding Path=ManufacturerImage}" Grid.Column="0"/>
        <TextBlock x:Name="txtManufacturer" Grid.Column="1" HorizontalAlignment="Left"
                   VerticalAlignment="Center" Text="{Binding Path=ManufacturerName}"
                   Tag="{Binding Path=ManufacturerID}"/>
    </Grid>
</DataTemplate>


<ComboBox x:Name="cboManufacturer" 
          SelectionChanged="cboManufacturer_SelectionChanged"
          ItemsSource = "{Binding Path=CurrentManufacturers}"                        
          SelectedValue="{Binding Path=SelectedManufacturer}"                        
          Grid.Column="3" Grid.Row="2"  Margin="20,9.25,68,7.75"  
          ItemTemplate="{StaticResource ManufacturerDataTemplate}" TabIndex="6"/>

这是我在 viewModel 后面的代码部分。

List<tblManufacturer> currentManufacturers
        = new List<tblManufacturer>();

tblManufacturer selectedManufacturer = null;

public List<tblManufacturer> CurrentManufacturers
{
    get
    {
        return currentManufacturers;
    }
    set
    {
        currentManufacturers = value;
        NotifyPropertyChanged("CurrentManufacturers");
    }
}

public tblManufacturer SelectedManufacturer
{
    get
    {
        return selectedManufacturer;
    }
    set
    {
        selectedManufacturer = currentManufacturers.Where(mm => mm.ManufacturerID == Convert.ToInt32(selectedDevice.tblManufacturer.EntityKey.EntityKeyValues[0].Value)).First();
        NotifyPropertyChanged("SelectedManufacturer");
    }
}

Answer 1

这里是示例代码sn-p：

组合框的 Xaml：

 <ComboBox ItemsSource="{Binding ManufacturerList}" DisplayMemberPath="Name" SelectedValuePath="ID"
              SelectedItem="{Binding SelectedManufacturer}"/>

ViewModel 代码：

 public class Manufacturer
{
    public int ID { get; set; }

    public string Name { get; set; }
}





 private List<Manufacturer> _manufactuerlist;
   private Manufacturer _selectedManufacturer;

 private void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

#region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
    public Manufacturer  SelectedManufacturer
    {
        get
        {
          return _selectedManufacturer;
        }
        set
        {
            _selectedManufacturer = value;
            NotifyPropertyChanged("SelectedManufacturer");
        }
    }

    public List<Manufacturer> ManufacturerList
    {
        get
        {
            return _manufactuerlist;
        }
        set
        {
            _manufactuerlist = value;
            NotifyPropertyChanged("ManufacturerList");
        }
    }

最后在您的视图模型中设置选定的制造商，如下所示：

SelectedManufacturer = _manufactuerlist.Find(m => m.ID == 2);