如何知道我的linq查询是否返回null [英] how to know if my linq query returns null

问题描述

我有这个linq查询:

I have this linq query :

var myQuery = from Q in myDataContext
          select Q.Name

，当我尝试这样做时: listView.ItemsSource = myQuery

and when I try to do this : listView.ItemsSource = myQuery

有时会抛出异常，因为myQuery

it sometimes throws an exception because there are no elements in myQuery

我尝试了很多方法，例如:if(myQuery.count!=0)或if(myQuery.Any()) 但没有任何效果，那么如何确定查询是否返回空值?

I tried many ways like : if(myQuery.count!=0) or if(myQuery.Any()) but nothing worked , so how can I determine if my Query return null ?

推荐答案

您可以将结果显示为列表:

You can realise the result as a list:

var myQuery = (from Q in myDataContext select Q.Name).ToList();

现在您可以检查项目数:

Now you can check the number of items:

if (myQuery.Count > 0) ...

您还可以在原始查询上使用Count()方法，但是随后您将运行两次查询，一次对项目进行计数，一次来使用它们.

You could also use the Count() method on the original query, but then you would be running the query twice, once to count the items, and once to use them.

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