我对Kiran Challa的答案有些问题,这是我的修改。
问题出在方法中。
private IEnumerable<FilterInfo> OrderFilters(IEnumerable<IFilter> filters, FilterScope scope)
{
return filters.OfType<IOrderedFilter>()
.OrderBy(filter => filter.Order)
.Select(instance => new FilterInfo(instance, scope));
}
你可以看到,只有实现了IOrderedFilter
接口的筛选器才会被返回。我有一个第三方属性被删掉了,因此没有被执行。
所以我有两个可能的解决方案:
- 使用继承创建第三方属性的扩展版本,使它也实现
IOrderFilter
接口。
- 更改方法,将每个未实现
IOrderFilter
接口的属性视为具有排序号为0的IOrderFilter
属性,并将其与IOrderFilter
属性组合排序并返回。
第二种解决方案更好,因为它允许我将我的IOrderFilter
属性放在不实现IOrderFilter
接口的第三方属性之前。
示例
[NonOrderableThirdPartyAttribute]
[OrderableAttributeA(Order = -1)]
[OrderableAttributeB(Order = 1)]
[OrderableAttributeC(Order = 2)]
public async Task<IHttpActionResult> Post(... request)
{
// do something
}
因此执行顺序将会是
- OrderableAttributeA
- NonOrderableThirdPartyAttribute
- OrderableAttributeB
- OrderableAttributeC
这里是修改后的代码
public class OrderedFilterProvider : IFilterProvider
{
public IEnumerable<FilterInfo> GetFilters(HttpConfiguration configuration, HttpActionDescriptor actionDescriptor)
{
// controller-specific
var controllerSpecificFilters = OrderFilters(actionDescriptor.ControllerDescriptor.GetFilters(), FilterScope.Controller);
// action-specific
var actionSpecificFilters = OrderFilters(actionDescriptor.GetFilters(), FilterScope.Action);
return controllerSpecificFilters.Concat(actionSpecificFilters);
}
private IEnumerable<FilterInfo> OrderFilters(IEnumerable<IFilter> filters, FilterScope scope)
{
// get all filter that dont implement IOrderedFilter and give them order number of 0
var notOrderableFilter = filters.Where(f => !(f is IOrderedFilter))
.Select(instance => new KeyValuePair<int, FilterInfo>(0, new FilterInfo(instance, scope)));
// get all filter that implement IOrderFilter and give them order number from the instance
var orderableFilter = filters.OfType<IOrderedFilter>().OrderBy(filter => filter.Order)
.Select(instance => new KeyValuePair<int, FilterInfo>(instance.Order, new FilterInfo(instance, scope)));
// concat lists => order => return
return notOrderableFilter.Concat(orderableFilter).OrderBy(x => x.Key).Select(y => y.Value);
}
}