Silverlight组合框-设置SelectedItem MVVM

我有一个ViewModel，它设置“UserStructure”属性的值。问题是组合框不会绑定到该值

public class OwnerOccupierAccountViewModel : ViewModelBase
{
    /// <summary>
    /// Load combobox structures
    /// </summary>
    private readonly LoadOperation<Structure> _loadStructures;

    private readonly LoadOperation<UnitOccupierDetail> _loadUnitOccupierDetails;

    //public ICommand SaveAccountSettingsCommand { get; set; }

    #region Properties

    private ObservableCollection<Structure> _structures;
    public ObservableCollection<Structure> Structures
    {
        get { return _structures; }

        set
        {
            _structures = value;
            RaisePropertyChanged("Structures");
        }
    }

    private Structure _userStructure;
    public Structure UserStructure
    {
        get { return _userStructure; }
        set
        {
            _userStructure = value;
            RaisePropertyChanged("SelectedStructure");
        }
    }

    private UnitOccupierDetail _unitOccupierDetail;
    public UnitOccupierDetail UnitOccupierDetail
    {
        get { return _unitOccupierDetail; }
        set
        {
            _unitOccupierDetail = value;
            RaisePropertyChanged("UnitOccupierDetail");
        }
    }


    #endregion

    public OwnerOccupierAccountViewModel()
    {
        // SaveAccountSettingsCommand = new DelegateCommand(SaveAccountSettings, CanSave);

        UserAccountContext _userAccountContext;

        if (!DesignerProperties.IsInDesignTool)
        {
            var loggedInUser = new Guid(WebContext.Current.User.UserID.ToString());

            _userAccountContext = new UserAccountContext();

            #region load structures
            _loadStructures = _userAccountContext.Load(_userAccountContext.GetStructuresQuery());
            _loadStructures.Completed += _loadStructuresCompleted;
            #endregion

            #region load user data 
            _loadUnitOccupierDetails =
                _userAccountContext.Load(
                    _userAccountContext.GetUnitOccupierDetailsQuery().Where(
                        u => u.UserIDFK == loggedInUser && u.StructureFK == 92));
            _loadUnitOccupierDetails.Completed += _loadUnitOccupierDetails_Completed;
            #endregion
        }
    }

    void _loadUnitOccupierDetails_Completed(object sender, EventArgs e)
    {
        _unitOccupierDetail= new UnitOccupierDetail();
        _unitOccupierDetail = _loadUnitOccupierDetails.Entities.First();

        _userStructure = _unitOccupierDetail.Structure;
    }

    void _loadStructuresCompleted(object sender, EventArgs e)
    {
        var theseStructures = new ObservableCollection<Structure>(_loadStructures.Entities);
        Structures = theseStructures;
    }

    //private void SaveAccountSettings(object param)
    //{

    //}

    //private static bool CanSave(object param)
    //{
    //    return true;
    //}
}

 <ComboBox x:Name="cboApartments" 
                          ItemsSource='{Binding Structures, Mode=TwoWay}'
                          DisplayMemberPath='StructureName'
                          SelectedValuePath='IDStructure'
                          SelectedItem='{Binding SelectedStructure,Mode=TwoWay}'
                          Width="200"
                          Height="25">

公共类OwnerOccupierAccountViewModel:ViewModelBase
{
/// 
///加载组合框结构
/// 
私有只读LoadOperation\u loadStructures；
私有只读LoadOperation\u loadUnitOccupierDetails；
//公共ICommand SaveAccountSettingsCommand{get；set；}
#区域属性
私有可观测集合结构；
公共收集结构
{
获取{return\u structures；}
设置
{
_结构=价值；
RaiseProperty变更（“结构”）；
}
}
私有结构——用户结构；
公共结构用户结构
{
获取{return\u userStructure；}
设置
{
_用户结构=值；
RaisePropertyChanged（“SelectedStructure”）；
}
}
私人单位占用详细信息(单位占用详细信息);；
公共单位占用者详细信息单位占用者详细信息
{
获取{return\u unitOccupierDetail；}
设置
{
_unitOccupierDetail=值；
RaisePropertyChanged（“UnitOccupierDetail”）；
}
}
#端区
public OwnerOccupierAccountViewModel（）
{
//SaveAccountSettingsCommand=newdelegateCommand（SaveAccountSettings，CanSave）；
UserAccountContext\u UserAccountContext；
如果（！DesignerProperties.IsInDesignTool）
{
var loggedInUser=newGUID（WebContext.Current.User.UserID.ToString（））；
_userAccountContext=新的userAccountContext（）；
#区域荷载结构
_loadStructures=\u userAccountContext.Load（\u userAccountContext.GetStructuresQuery（））；
_loadStructures.Completed+=\u loadStructuresCompleted；
#端区
#区域加载用户数据
_loadUnitOccupierDetails=
_userAccountContext.Load(
_userAccountContext.GetUnitOccupierDetailsQuery（）。其中(
u=>u.UserIDFK==loggedInUser&&u.StructureFK==92））；
_loadUnitOccupierDetails.Completed+=\u loadUnitOccupierDetails\u Completed；
#端区
}
}
void\u loadUnitOccupierDetails\u已完成（对象发送方，事件参数e）
{
_unitOccupierDetail=新的unitOccupierDetail（）；
_unitOccupierDetail=\u loadUnitOccupierDetails.Entities.First（）；
_userStructure=\u unitOccupierDetail.Structure；
}
void\u loadStructuresCompleted（对象发送方，事件参数e）
{
var theseStructures=新的ObservableCollection（_loadStructures.Entities）；
结构=这些结构；
}
//私有void SaveAccountSettings（对象参数）
//{
//}
//私有静态bool CanSave（对象参数）
//{
//返回true；
//}
}

尝试这些更改

public class OwnerOccupierAccountViewModel : ViewModelBase
{
    /// <summary>
    /// Load combobox structures
    /// </summary>
    private readonly LoadOperation<Structure> _loadStructures;

    private readonly LoadOperation<UnitOccupierDetail> _loadUnitOccupierDetails;

    //public ICommand SaveAccountSettingsCommand { get; set; }

    #region Properties

    private ObservableCollection<Structure> _structures;
    public ObservableCollection<Structure> Structures
    {
        get { return _structures; }

        set
        {
            _structures = value;
            RaisePropertyChanged("Structures");
        }
    }

    private Structure _userStructure;
    public Structure UserStructure
    {
        get { return _userStructure; }
        set
        {
            _userStructure = value;
            RaisePropertyChanged("UserStructure");
        }
    }

    private UnitOccupierDetail _unitOccupierDetail;
    public UnitOccupierDetail UnitOccupierDetail
    {
        get { return _unitOccupierDetail; }
        set
        {
            _unitOccupierDetail = value;
            RaisePropertyChanged("UnitOccupierDetail");
        }
    }


    #endregion

    public OwnerOccupierAccountViewModel()
    {
        // SaveAccountSettingsCommand = new DelegateCommand(SaveAccountSettings, CanSave);

        UserAccountContext _userAccountContext;

        if (!DesignerProperties.IsInDesignTool)
        {
            var loggedInUser = new Guid(WebContext.Current.User.UserID.ToString());

            _userAccountContext = new UserAccountContext();

            #region load structures
            _loadStructures = _userAccountContext.Load(_userAccountContext.GetStructuresQuery());
            _loadStructures.Completed += _loadStructuresCompleted;
            #endregion

            #region load user data 
            _loadUnitOccupierDetails =
                _userAccountContext.Load(
                    _userAccountContext.GetUnitOccupierDetailsQuery().Where(
                        u => u.UserIDFK == loggedInUser && u.StructureFK == 92));
            _loadUnitOccupierDetails.Completed += _loadUnitOccupierDetails_Completed;
            #endregion
        }
    }

    void _loadUnitOccupierDetails_Completed(object sender, EventArgs e)
    {
        _unitOccupierDetail= new UnitOccupierDetail();
        _unitOccupierDetail = _loadUnitOccupierDetails.Entities.First();

        _userStructure = _unitOccupierDetail.Structure;
    }

    void _loadStructuresCompleted(object sender, EventArgs e)
    {
        var theseStructures = new ObservableCollection<Structure>(_loadStructures.Entities);
        Structures = theseStructures;
    }

    //private void SaveAccountSettings(object param)
    //{

    //}

    //private static bool CanSave(object param)
    //{
    //    return true;
    //}
}

 <ComboBox x:Name="cboApartments" 
                          ItemsSource='{Binding Structures, Mode=TwoWay}'
                          DisplayMemberPath='StructureName'
                          SelectedValuePath='IDStructure'
                          SelectedItem='{Binding UserStructure,Mode=TwoWay}'
                          Width="200"
                          Height="25">

公共类OwnerOccupierAccountViewModel:ViewModelBase
{
/// 
///加载组合框结构
/// 
私有只读LoadOperation\u loadStructures；
私有只读LoadOperation\u loadUnitOccupierDetails；
//公共ICommand SaveAccountSettingsCommand{get；set；}
#区域属性
私有可观测集合结构；
公共收集结构
{
获取{return\u structures；}
设置
{
_结构=价值；
RaiseProperty变更（“结构”）；
}
}
私有结构——用户结构；
公共结构用户结构
{
获取{return\u userStructure；}
设置
{
_用户结构=值；
RaisePropertyChanged（“用户结构”）；
}
}
私人单位占用详细信息(单位占用详细信息);；
公共单位占用者详细信息单位占用者详细信息
{
获取{return\u unitOccupierDetail；}
设置
{
_unitOccupierDetail=值；
RaisePropertyChanged（“UnitOccupierDetail”）；
}
}
#端区
public OwnerOccupierAccountViewModel（）
{
//SaveAccountSettingsCommand=newdelegateCommand（SaveAccountSettings，CanSave）；
UserAccountContext\u UserAccountContext；
如果（！DesignerProperties.IsInDesignTool）
{
var loggedInUser=newGUID（WebContext.Current.User.UserID.ToString（））；
_userAccountContext=新的userAccountContext（）；
#区域荷载结构
_loadStructures=\u userAccountContext.Load（\u userAccountContext.GetStructuresQuery（））；
_loadStructures.Completed+=\u loadStructuresCompleted；
#端区
#区域加载用户数据
_loadUnitOccupierDetails=
_userAccountContext.Load(
_userAccountContext.GetUnitOccupierDetailsQuery（）。其中(
u=>u.UserIDFK==loggedInUser&&u.StructureFK==92））；
_loadUnitOccupierDetails.Completed+=\u loadUnitOccupierDetails\u Completed；
#端区
}
}
void\u loadUnitOccupierDetails\u已完成（对象发送方，事件参数e）
{
_unitOccupierDetail=新的unitOccupierDetail（）；
_unitOccupierDetail=\u loadUnitOccupierDetails.Entities.First（）；
_userStructure=\u unitOccupierDetail.Structure；
}
void\u loadStructuresCompleted（对象发送方，事件参数e）
{
var theseStructures=新的ObservableCollection（_loadStructures.Entities）；
结构=这些结构；
}
//私有void SaveAccountSettings（对象参数）
//{
//}
//私有静态bool CanSave（对象参数）
//{
//返回true；
//}
}

更新：

嗯，也许可以在这里尝试更改：

     <ComboBox x:Name="cboApartments" 
                              ItemsSource='{Binding Structures, Mode=TwoWay}'
                              SelectedItem='{Binding UserStructure, Mode=TwoWay}'
                              Width="200"
                              Height="25">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Path=StructureName}"/>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>

---

在您的XAML SelectedItem中，它绑定到SelectedStructure，而不是您需要的UserStructure

   void _loadUnitOccupierDetails_Completed(object sender, EventArgs e)
   {
        ...

        Structure userStructure = Structures.FirstOrDefault(s=>s.Equals(_unitOccupierDetail.Structure));
        UserStructure = userStructure;
   }