使用Linq从2个不同的对象中进行选择

Question

i want to select from 2 different objects in Linq in order to compare them. This is what i tried,

var myItem = (from abc in firstList.Value
              from cds in secondList
              where (abc.Key.theKey == cds.secondList.theSecondKey
              select cds).SingleOrDefault();

although i get an error:

Type inference failed in the call to 'SelectMany'

Answer 1

If that's your exact query, it may just be because you've got unmatched brackets. Try this:

var myItem = (from abc in firstList.Value
              from cds in secondList
              where abc.Key.theKey == cds.secondList.theSecondKey
              select cds).SingleOrDefault();

Admittedly I would probably rewrite that using a join - in most cases the join will be more efficient.

However, if that's not your exact query, please post a short but complete program which demonstrates the problem. It's not clear why cds would have a secondList property for example. A complete example demonstrating the problem would make this a lot simpler.

Answer 2

You have an opening paranthesis in more:

var myItem = (from abc in firstList.Value
              from cds in secondList
              where abc.Key.theKey == cds.secondList.theSecondKey
              select cds
             ).SingleOrDefault();