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Linq: Is there a way to search a list of objects for values ​​that match a condition?

I have 3 types of objects, TypeA, TypeB, TypeC. TypeA has a list of TypeB and TypeB has a list of TypeC and TypeC has some variables that I want to keep track of

Class TypeA
{
  List<TypeB> MyListOfTypeB;
  //...
}

Class TypeB
{
  List<TypeC> MyListOfTypeC;
  //...
}

Class TypeC
{
  int SomeInteger;
  //...
}

Given List<TypeA> MyListOfTypeA

, I want to search for all TypeC objects that satisfy a certain condition, like SomeInteger> 100. Besides embedding in / foreach loops, what is the Linq way of doing this?

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4 answers 


var MyListOfTypeA = new List<TypeA>();
// ...
var cItems = 
    from a in MyListOfTypeA
    from b in a.MyListOfTypeB
    from c in a.MyListOfTypeC
    where c.SomeInteger > 100
    select c;

The above is equivalent to a SelectMany

LINQ function call , but in my opinion it is significantly cleaner and easier to read.



Doing this with LINQ functions (as already suggested by Dmitry, albeit with some modifications):

var cItems = 
    MyListOfTypeA.SelectMany( a => a.MyListOfTypeB )
                 .SelectMany( b => b.MyListOfTypeC )
                 .Where( c => c.SomeValue > 200 );
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Something like this is what you are looking for, I think:



var result = MyListOfTypeA.SelectMany(b => b.MyListOfTypeB.SelectMany(c => c.MyListOfTypeC.Select(x => x.SomeInteger > 100))).ToList();
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You can do it like this using Linq:

    var myListOfTypeA = new List<TypeA>();

    // fill your list here

    var typeCs = from typeA in myListOfTypeA
                 from typeB in typeA.MyListOfTypeB
                 from typeC in typeB.MyListOfTypeC
                 where typeC.SomeInteger > 100
                 select typeC;
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You need to navigate through all sublists and what from

can do for you.

var ta = new TypeA();

var allTypeCsThatSatisfyMyCondition = 
    from tb in ta.MyListOfTypeB                     // This will iterate to each item in the list
    from tc in tb.MyListOfTypeC                     // This will iterate to each item in the *sublist*
    where tc.SomeInteger > 100          // Condition could be anything; filter the results
    select tc;                                      // When you select, you tell your iterator to yield return that value to the caller.

return allTypeCsThatSatisfyMyCondition.ToList();    // To list will force the LINQ to execute and iterate over all items in the lists, and add then to a list, effectively converting the returned items to a list.
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