WebAPI OData预过滤扩展查询

我想知道是否有可能对扩展子句中的项在WebAPI中预过滤OData结果。我只希望它基于带有Deleted标志的预定义接口进行过滤。

public interface IDbDeletedDateTime
{
    DateTime? DeletedDateTime { get; set; }
}
public static class IDbDeletedDateTimeExtensions
{
    public static IQueryable<T> FilterDeleted<T>(this IQueryable<T> self) 
        where T : IDbDeletedDateTime
    {
        return self.Where(s => s.DeletedDateTime == null);
    }
}
public class Person : IDbDeletedDateTime
{
     [Key]
     public int PersonId { get; set }
     public DateTime? DeletedDateTime { get; set; }
     public virtual ICollection<Pet> Pets { get; set; }
}
public class Pet : IDbDeletedDateTime
{
     [Key]
     public int PetId { get; set }
     public int PersonId { get; set }
     public DateTime? DeletedDateTime { get; set; }
}

public class PersonController : ApiController
{
    private PersonEntities db = new PersonEntities();
    [EnableQuery]
    // GET: api/Persons
    public IQueryable<Person> GetPersons()
    {
        return db.Persons.FilterDeleted();
    }
}

你可以看到我很容易过滤已删除的人。问题来了，当有人从像/api/Persons的查询中删除宠物?扩大美元=宠物

是否有一种方法来检查"宠物"的扩展是否为IDbDeletedDateTime并相应地过滤它们?也许有更好的方法来解决这个问题?

我试着根据这个答案中的内容来解决这个问题。我不认为这是可以做到的，至少不是在所有情况下。ExpandedNavigationSelectItem中唯一看起来与滤波器有关的部分是FilterClause。当它没有过滤器并且它只是一个getter属性时，它可以为空，这意味着我们不能设置一个新的过滤器，如果我们想。是否有可能修改当前的过滤器只覆盖了一个小的用例，如果我不能添加一个新的过滤器，我不是特别感兴趣。

我有一个扩展方法，它将递归通过所有的展开子句，你至少可以看到每个展开的FilterOption是什么。如果有人能完全实现这90%的代码，那将是惊人的，但我并没有屏住呼吸。

public static void FilterDeletables(this ODataQueryOptions queryOptions)
{
    //Define a recursive function here.
    //I chose to do it this way as I didn't want a utility method for this functionality. Break it out at your discretion.
    Action<SelectExpandClause> filterDeletablesRecursive = null;
    filterDeletablesRecursive = (selectExpandClause) =>
    {
        //No clause? Skip.
        if (selectExpandClause == null)
        {
            return;
        }
        foreach (var selectedItem in selectExpandClause.SelectedItems)
        {
            //We're only looking for the expanded navigation items. 
            var expandItem = (selectedItem as ExpandedNavigationSelectItem);
            if (expandItem != null)
            {
                //https://msdn.microsoft.com/en-us/library/microsoft.data.odata.query.semanticast.expandednavigationselectitem.pathtonavigationproperty(v=vs.113).aspx
                //The documentation states: "Gets the Path for this expand level. This path includes zero or more type segments followed by exactly one Navigation Property."
                //Assuming the documentation is correct, we can assume there will always be one NavigationPropertySegment at the end that we can use. 
                var edmType = expandItem.PathToNavigationProperty.OfType<NavigationPropertySegment>().Last().EdmType;
                string stringType = null;
                IEdmCollectionType edmCollectionType = edmType as IEdmCollectionType;
                if (edmCollectionType != null)
                {
                    stringType = edmCollectionType.ElementType.Definition.FullTypeName();
                }
                else
                {
                    IEdmEntityType edmEntityType = edmType as IEdmEntityType;
                    if (edmEntityType != null)
                    {
                        stringType = edmEntityType.FullTypeName();
                    }
                }
                if (!String.IsNullOrEmpty(stringType))
                {
                    Type actualType = typeof(PetStoreEntities).Assembly.GetType(stringType);
                    if (actualType != null && typeof (IDbDeletable).IsAssignableFrom(actualType))
                    {
                        var filter = expandItem.FilterOption;
                        //expandItem.FilterOption = new FilterClause(new BinaryOperatorNode(BinaryOperatorKind.Equal, new , ));
                    }
                }
                filterDeletablesRecursive(expandItem.SelectAndExpand);
            }
        }
    };
    filterDeletablesRecursive(queryOptions.SelectExpand?.SelectExpandClause);
}