Silverob中的Combobox显示值

> Xaml

<my:MyComboBox Width="180" Itemssource="{Binding TestItems}" Text="{Binding SELEctedItemsText}">
    <my:MyComboBox.ItemTemplate>
        <DataTemplate>
            <Grid HorizontalAlignment="Left">
                <checkBox Ischecked="{Binding Ischecked,Mode=TwoWay}" Content="{Binding Text}"/>
            </Grid>
        </DataTemplate>
    </my:MyComboBox.ItemTemplate>
</my:MyComboBox>

>组合框的黑客：

public class MyComboBox : ComboBox
{
private ContentPresenter SELEctedContent;


public MyComboBox()
{
    this.DefaultStyleKey = typeof(ComboBox);
}


public override void OnApplyTemplate()
{
    this.SELEctedContent = this.GetTemplateChild("ContentPresenter") as ContentPresenter;
    this.refreshContent();
    base.onApplyTemplate();
    this.SELEctionChanged += (s,E) =>
        {
            //Cancel SELEction
            this.SELEctedItem = null;
            this.refreshContent();
        };
}


public String Text
{
    get { return (String)GetValue(TextProperty); }
    set { SETVALue(TextProperty,value); }
}


public static readonly DependencyProperty TextProperty =
    DependencyProperty.Register("Text",typeof(String),typeof(MyComboBox),new PropertyMetadata(null,new PropertyChangedCallBACk((s,E)=>((MyComboBox)s).refreshContent())));


private void refreshContent()
{
    if (this.SELEctedContent != null)
    {
        var tb = (TextBlock)this.SELEctedContent.Content;
        tb.Text = this.Text;
    }
}
}

> Mainviewmodel

public class Mainviewmodel : INotifyPropertyChanged
{
public Mainviewmodel()
{
    this.InitializeTestItems();
}


public void InitializeTestItems()
{
    this.TestItems = new List<TestItemModel>{
                new TestItemModel{Ischecked=true,Text="first"},new TestItemModel{Ischecked=false,Text="second"},Text="third"}};
    this.refreshSELEctedItemsText();
    foreach (var item in this.TestItems)
        item.checkChanged += (s,E) => this.refreshSELEctedItemsText();
}


private void refreshSELEctedItemsText()
{
    SELEctedItemsText = String.Join(",",this.TestItems.Where(ti => ti.Ischecked).SELEct(ti => ti.Text));
}


public List<TestItemModel> TestItems { get; set; }


private String SELEctedItemsText;


public String SELEctedItemsText
{
    get { return SELEctedItemsText; }
    set
    {
        SELEctedItemsText = value;
        OnPropertyChanged("SELEctedItemsText");
    }
}
}

4.Itemviewmodel

public class TestItemModel
{
    private bool ischecked;

    public bool Ischecked
    {
        get { return ischecked; }
        set 
        { 
            ischecked = value;
            if (checkChanged != null)
                checkChanged(this,null);
        }
    }

    public String Text { get; set; }

    public event EventHandler<EventArgs> checkChanged;
}