ComboBox所选项目未更新

Question

Problem

I am trying to bind a ComboBox's SelectedItem to a custom class but this does not update when the property is changed. INotifyPropertyChanged is implemented.

The DataContext

The DataContext is a custom class which contains many properties, but an extract of this is below. You can see it implements INotifyPropertyChanged and this called when the two properties are changed.

public class BctsChange : INotifyPropertyChanged
{
    #region declarations
    private byContact _Engineer;

    public byContact Engineer
    {
        get { return _Engineer; }
        set
        {
            _Engineer = value;
            NotifyPropertyChanged("Engineer");
            OnEngineerChanged();
        }
    }

    private BctsSvc.DOSets _LeadingSet;

    public BctsSvc.DOSets LeadingSet
    {
        get { return _LeadingSet; }
        set { _LeadingSet = value; NotifyPropertyChanged("LeadingSet"); }
    }
    #endregion

    #region INotify
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    #endregion

    public BctsChange()
    {
        Engineer = new byContact(Environment.UserName);
    }

    private void OnEngineerChanged()
    {
        if (Engineer != null)
        {
            BctsSvc.DOSets leadSet = GetLeadingSetFromDeptCode(Engineer.DeptCode);

            if (leadSet == null) return;
            LeadingSet = leadSet;
        }
    }


    private static BctsSvc.DOSets GetLeadingSetFromDeptCode(string DeptCode)
    {
        BctsSvc.BctsServiceSoapClient svc = new BctsSvc.BctsServiceSoapClient();
        BctsSvc.DOSets setX = svc.GetSetFromDeptCode(DeptCode);
        return setX;
    }
}

The Window XAML

I have several controls on the window, but to keep the code simple I believe the following extract will suffice.

<Window x:Class="MyNamespace.wdSubmit"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:my="clr-namespace:MyNamespace"
            xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
            x:Name="ucReqForm"
        Title="wdSubmit" >
    <StackPanel Orientation="Vertical" HorizontalAlignment="Stretch">        
        <GroupBox Header="Engineer Details" Name="grpOwnerDetails" >
            <StackPanel Orientation="Vertical">
                <Grid VerticalAlignment="Top">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="35"/>
                    </Grid.ColumnDefinitions>
                    <Label Content="{Binding Engineer.FullName,  FallbackValue='Please select an engineer by clicking →', Mode=OneWay}" Margin="5,0" IsEnabled="True" FontStyle="Italic" />
                    <Button Content="{StaticResource icoSearch}" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" Grid.Column="1" Height="23" Name="btnSelectEngineer" Margin="0,0,5,0" HorizontalAlignment="Stretch" ToolTip="Search for an engineer responsible" Click="btnSelectEngineer_Click" />
                </Grid>

                <ComboBox Height="23" x:Name="ddSet2" Margin="5,0" ItemsSource="{Binding LeadingSets, Mode=OneWay, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" SelectedItem="{Binding LeadingSet, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged,NotifyOnTargetUpdated=True}" >
                    <ComboBox.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding SetName}" ToolTip="{Binding HelpInfo}"/>
                        </DataTemplate>
                    </ComboBox.ItemTemplate>
                </ComboBox>
                <my:LabelledDropdown Height="23" x:Name="ddSet" Margin="5,0" ItemsSource="{Binding LeadingSets, Mode=OneWay, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Window}}" SelectedItem="{Binding LeadingSet, Mode=TwoWay,NotifyOnTargetUpdated=True,NotifyOnSourceUpdated=True}" Label="e.g. BodyHardware">
                    <my:LabelledDropdown.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding SetName}" ToolTip="{Binding HelpInfo}"/>
                        </DataTemplate>
                    </my:LabelledDropdown.ItemTemplate>
                </my:LabelledDropdown>
            </StackPanel>
        </GroupBox>
    </StackPanel>
</Window>

The above extract contains:

• A Label that contains a contact's name, and a button to search for a contact, bound to the FullName of the Engineer
• A ComboBox that contains departments within the company, bound to an ObservableCollection<DOSets> , which contains a list of departments
• Two ComboBox es, one which is a custom one and the other which is temporary to ensure the bug is not within the control. These are Databound to LeadingSet

Window Code Behind

In the code behind I set the DataContext to CurrentChange . When the user wants to select a different Engineer then this will update the selected department for the engineer in CurrentChange .

When the user changes the engineer, the data binding for the engineer is updated, but the selected department (Leading Set) isn't.

//Usings here

namespace MyNamespace
{
    public partial class wdSubmit : Window, INotifyPropertyChanged
    {
        private BctsSvc.BctsServiceSoapClient svc;

        private BctsChange _CurrentChange;

        public BctsChange CurrentChange
        {
            get { return _CurrentChange; }
            set { _CurrentChange = value; OnPropertyChanged("CurrentChange"); }
        }


        private List<BctsSvc.DOSets> _LeadingSets;
        public List<BctsSvc.DOSets> LeadingSets
        {
            get
            {
                return _LeadingSets;
            }
        }


        public wdSubmit()
        {
            InitializeComponent();
            svc = new BctsSvc.BctsServiceSoapClient();
            _LeadingSets = svc.GetLeadSets().ToList();
            OnPropertyChanged("LeadingSets");

            this._CurrentChange = new BctsChange();

            this.DataContext = CurrentChange;

            CurrentChange.PropertyChanged += new PropertyChangedEventHandler(CurrentChange_PropertyChanged);
        }

        void CurrentChange_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            OnPropertyChanged("CurrentChange");
            OnPropertyChanged(e.PropertyName);
        }

        private void btnSelectEngineer_Click(object sender, RoutedEventArgs e)
        {
            byContact newContact = new frmSearchEngineer().ShowSearch();

            if (newContact != null)
            {
                CurrentChange.Engineer = newContact;
                PropertyChanged(CurrentChange, new PropertyChangedEventArgs("LeadingSet"));
                PropertyChanged(CurrentChange.LeadingSet, new PropertyChangedEventArgs("LeadingSet"));

            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(CurrentChange, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Answer 1

我已经意识到问题可能是由于LeadingSet所致，该LeadingSet是在更换工程师时返回的，与ObservableCollection中的实例不同。