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I am stucked in a situation where I am having two lists. What will be the correct way to compare the two and get the result in third list. But here is a small catch. See example below:

ListOld = { [Name=Amit, Class=V, Roll=3], [Name=Naveen, Class=V, Roll=3], [Name=Sammy, Class=V, Roll=3], [Name=Neil, Class=X, Roll=21], [Name=John, Class=VI, Roll=63]}; ListNew = { [Name=Amit, Class=VI, Roll=13], [Name=Naveen, Class=VII, Roll=3], [Name=Sammy, Class=V, Roll=3], [Name=Sanjay, Class=VIII, Roll=2]}; ResultantList = { [Name=Amit, Class=VI, Roll=13], [Name=Naveen, Class=VII, Roll=3], [Name=Sanjay, Class=VIII, Roll=2]};

In above example, ListNew has got 3 changes, that are updates in Amit and Naveen , and Sanjay as a new member.

So In my query I need to compare both the list and want to pick either updated or added item in first list.

I tried, Except(), Intersect(), union(), with Equality Interfaces but no success. Kindly help.

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You can do it by writing an IEqualityComparer

public class SomeClassComparer : IEqualityComparer<SomeClass> { public bool Equals(SomeClass x, SomeClass y) { return x.Name == y.Name && x.Class == y.Class && x.Roll == y.Roll; } public int GetHashCode(SomeClass obj) { return (obj.Name + obj.Class).GetHashCode(); } }

Now, the linq is simple

var result = ListNew.Except(ListOld , new SomeClassComparer()).ToList();

You can also do the same thing by overiding ToString and GetHashcode methods, but IEqualityComparer is good especially when you have no control over the class you use.

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2 Comments

Thanks but the same I tried and it didn't worked. AFAIK Equality Comparing interfaces work only when we have similaritirs. But here inmy case. I need to figure out the diference and pick those one
@AmitRanjan I also tested it and it works. How about posting a small, compilable test case showing what you have tried So that we can talk about the same code..