Silverlight中的组合框显示值 [英] Combobox display value in Silverlight

问题描述

我有ComboBox与复选框的项目。
当用户选中或取消选中复选框时，我想要将选定的值显示在ContentPresenter中，并以逗号分隔。
目前我已覆盖ContentPresenter：

I have ComboBox with CheckBoxes for items. When user checks or uncheckes boxes I want the selected values to be displayed in the ContentPresenter separated by comma. At the the moment I have overridden ContentPresenter:

<ContentPresenter x:Name="ContentPresenter"
    HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
    Margin="{TemplateBinding Padding}"
    VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
    ContentTemplate="{StaticResource SelectedOperationsText}"/>

ContentPresenter默认为ComboBox样式的一部分。
如何实现此功能的任何提示？

ContentPresenter is a part of ComboBox style by default. Any hints on how to implement this feature?

ComboBox ItemTemplate实现如下：

ComboBox ItemTemplate is implemented like this:

<DataTemplate x:Key="ComboItemTemplate">
     <Grid HorizontalAlignment="Left">
         <CheckBox IsChecked="{Binding IsChecked}" Content="{Binding Text}"/>
     </Grid>
</DataTemplate>

推荐答案

这个解决方案并不理想可以为继承自combobox的控件创建自定义控件模板）。

This solution isn't ideal (for example, you can create custom control template for control inherited from combobox), but it works.

1. Xaml

1. 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>

攻击组合框：

Hack of the combobox:

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

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"},
                new TestItemModel{IsChecked=false, 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");
    }
}
}

b $ b

4.ItemViewModel

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;
}

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