我如何判断一个IQueryable是IOrderedQueryable？ [英] How can I tell if an IQueryable is an IOrderedQueryable?

问题描述

我有一个IQueryable。我没有它被称为排序依据，或以其他方式做任何事的。

如果我做的：

  //由于某种原因，isItOrdered始终是真实的
 VAR isItOrdered = myQueryable是IOrderedQueryable< T> 
  

这是为什么总是如此？ （现在看来似乎不应该。），更重要的是，我怎么能告诉我们，如果一个IQueryable已经已经下令？ （即是真正的IOrderedQueryable）

我希望能够做一些事情，如：

 如果（myQueryable是IOrderedQueryable< T>）
 myQueryable = myQueryable.ThenBy（...）; 
，否则
 myQueryable = myQueryable.OrderBy（...）; 
  

解决方案

您还没有表现出什么创建可查询开始有，但也许它是自然以某种方式订购？

你有什么的确实的检查它是否是一个真正的 IOrderedQueryable< T> - 我怀疑这只是你的查询提供的总是的提供了一个有序的可查询，即使订单不明显

$ b $。 b

编辑：好的，别的东西，你可以尝试：

 如果（typeof运算（IOrderedQueryable< T> ）.IsAssignableFrom（myQueryable.Expression.Type））
  

...或一般，打印出 myQueryable.Expression.Type ，看看它是什么样子。

I have an IQueryable. I have not called OrderBy on it or otherwise done anything with it.

If I do:

// for some reason, isItOrdered is always true
var isItOrdered = myQueryable is IOrderedQueryable<T>

Why is this always true? (It seems like it shouldn't be.) And, more importantly, how can I tell if an IQueryable already has been ordered? (i.e. is truly an IOrderedQueryable)

I would like to be able to do something like:

if (myQueryable is IOrderedQueryable<T>)
  myQueryable = myQueryable.ThenBy(...);
else
  myQueryable = myQueryable.OrderBy(...);

解决方案

You haven't shown what's creating your queryable to start with, but perhaps it's naturally ordered in some way?

What you've got does check whether it's really an IOrderedQueryable<T> - I suspect that it's just that your query provider always provides an ordered queryable, even if the order isn't obvious.

EDIT: Okay, something else you might try:

if (typeof(IOrderedQueryable<T>).IsAssignableFrom(myQueryable.Expression.Type))

... or in general, print out myQueryable.Expression.Type and see what it looks like.

这篇关于我如何判断一个IQueryable是IOrderedQueryable？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！