【发布时间】：2015-10-14 13:10:07
【问题描述】：
我想知道是否可以在扩展子句中的项目的 WebAPI 中预过滤 OData 结果。我只希望它根据带有已删除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被删除的人。当有人从 /api/Persons?$expand=Pets
之类的查询中删除 Pets 时，就会出现问题有没有办法检查“宠物”的这种扩展是否是 IDbDeletedDateTime 并相应地过滤它们？也许有更好的方法来解决这个问题？
编辑：
我试图根据this answer 中的内容来解决这个问题。我不认为它可以做到，至少不是在所有情况下都可以。 ExpandedNavigationSelectItem 中唯一看起来与过滤器相关的部分是FilterClause。当它没有过滤器时，它可以为 null，它只是一个 getter 属性，这意味着如果我们愿意，我们不能用新的过滤器设置它。天气与否是否可以修改当前过滤器仅涵盖一个小用例，如果我不能重新添加过滤器，我并不特别感兴趣。
我有一个扩展方法，它将递归遍历所有扩展子句，您至少可以看到每个扩展的 FilterOption 是什么。如果有人能完全实现这 90% 的代码，那就太棒了，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);
}
【问题讨论】：
标签： c# asp.net-web-api odata