Silverlight ComboBox筛选器-全部显示

Question

在带有RIA Services的Silverlight5中，使用DomainDataSources。

我有一个绑定到DataGrid的过滤器ComboBox。

问题：如何在组合框顶部实现“全选”-当前已通过在数据库中放置ID = 0的行并在过滤器中使用IgnoredValue =“ 0”来实现

    <riaControls:DomainDataSource.FilterDescriptors>
        <riaControls:FilterDescriptor PropertyPath="AccountTypeID" Operator="IsEqualTo" IgnoredValue="0" Value="{Binding Path=SelectedItem.AccountTypeID,
            ElementName=AccountTypeComboBox, FallbackValue=0}"  />
    </riaControls:DomainDataSource.FilterDescriptors>         
</riaControls:DomainDataSource>

<riaControls:DomainDataSource x:Name="AccountTypeDataSource" AutoLoad="True" QueryName="GetAccountTypes" PageSize="15" LoadSize="30">
    <riaControls:DomainDataSource.DomainContext>
        <domain:xxxDomainContext />
    </riaControls:DomainDataSource.DomainContext>
</riaControls:DomainDataSource>

想要在将数据加载到ComboBox中之后手动添加“显示全部代码”

编辑感谢下面的马丁，我像这样工作：

private xxxDomainContext xxxDomainContext;

    public MainPage()
    {
        InitializeComponent();

        // Load up the AccountType ComboBox - instead of doing it in XAML
        // then add in the Select All via proxy class above
        xxxDomainContext = new xxxDomainContext();
        EntityQuery<AccountType> query = xxxDomainContext.GetAccountTypesQuery();
        LoadOperation loadOperation = xxxDomainContext.Load<AccountType>(query);

        // everything is async so need a callback, otherwise will get an empty collection when trying to iterate over it here
        loadOperation.Completed += AccountTypeLoadOperationCompleted;

和

 private void AccountTypeLoadOperationCompleted(object sender, System.EventArgs e)
        {
            // create new proxy class
            var listOfSelectableObjects = new List<SelectableObject<int>>();

            var selectAll = new SelectableObject<int> { Display = "Select All", KeyValue = 0};
            listOfSelectableObjects.Add(selectAll);

            // load values into new list
            foreach (var accountType in xxxDomainContext.AccountTypes)
            {
                var so = new SelectableObject<int>();
                so.Display = accountType.Description;
                so.KeyValue = accountType.AccountTypeID;
                listOfSelectableObjects.Add(so);
            }

            AccountTypeComboBox.ItemsSource = listOfSelectableObjects;
            // Set index to 0 otherwise a blank item will appear at the top and be selected
            AccountTypeComboBox.SelectedIndex = 0;
        }

Answer 1

过去，我是通过创建一个代理类来实现此目的的，例如带有显示，键和isDefault的SelectableValue，如下所示：

public class SelectableObject<K>
{
   public string Display { get; set; }
   public K KeyValue { get;set; }
   public bool IsDefaultSelection { get; set; }
}

这意味着我可以将例如要选择的项目列表转换为List<SelectableObject<int>> ，并可以选择向该列表添加一个额外的项目，即Display="Select All"和IsDefault=true而不是尝试直接绑定到列表。

希望能有所帮助。