如何计算包含特定元素的特定元素？

Question

Considering xml like:

<Main>
   <ActivityOne>
       <!-- this should be counted -->
       <TaskA>yes</TaskA>
       <TaskB>do do do</TaskB>
   </ActivityOne>
   <ActivityTwo>
       <ActivityFive>
           <TaskA>da da da</TaskA>
       </ActivityFive>
   </ActivityTwo>
       <ActivityOne>
           <!-- this should not be counted -->
           <TaskC>yadda yadda</TaskC>
       </ActivityOne>
   <ActivityThree>
       <ActivityOne>
           <!-- this should be counted -->
           <ActivityFour>
               <TaskA>yes</TaskA>
           </ActivityFour>
           <TaskC>nope</TaskC>
       </ActivityOne>
       <ActivityTwo>
           <TaskF>no</TaskF>
       </ActivityTwo>
   </ActivityThree>
   <ActivityFour>
       <TaskA>nope</TaskA>
   </ActivityFour>
</Main>

I am trying to count the number of "ActivityOne" elements that contain one or more "TaskA" elements anywhere within.

I tried this:

int count = xDoc.Descendants("ActivityOne").Where(x => x.Descendants("TaskA").Count() > 0).Count();

But it only seems to count the ActivityOne elements that have a TaskA deeper than a direct child.

Answer 1

The solution you have provided is totally fine:

int count = xDoc.Descendants("ActivityOne")
                .Where(x => x.Descendants("TaskA").Count() > 0)
                .Count();

I would like to add one more solution which can help you to solve this problem using XPath:

int count = xDoc.XPathSelectElements("//ActivityOne[descendant::TaskA]").Count();

It's a little bit shorter expression and, in my opinion, it's a better approach if you need to select some elements from XML using special conditions.