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I have the following code in C# which checks if items in a list are equal (a list of integers for all practical purposes):

intList.Distinct().Count() == 1

The above code works if all values in the list are equal.

However if I have a scenario where: 

intList = {1, 1, 0}

then the above code fails. Can someone please suggest how I can check similar values in a list when all values in the list many not be equal.

Mafii
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ekartik
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    Can you please clarify what you mean by similar values? Do you want more than a true/false output? Do you want all pairs of identical values? – Tudor Jul 06 '18 at 10:01
  • Do you want to check whether the list contains only unique values? Or what is your exact goal? Please try to be more specific and declare your expected inputs and outputs. – Mafii Jul 06 '18 at 10:50

3 Answers3

4

How about

bool isDup = intList.Count == intList.Distinct().Count();
Ray Krungkaew
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if (intList.Distinct().Count() != intList.Count)
{
   // the list contained at least two values that were the same
}
nvoigt
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Linq Group() and Count() the groups

bool allUnique = intList.GroupBy(x => x).All(x => x.Count() == 1);

by using HashSet()

bool allUnique = new HashSet<int>(intList).Count == intList.Count;
fubo
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  • creating a hashset is usually a good idea, but not for just using it's count property. That's unnecessary overhead. Distinct does exactly the same technically speaking, just without creating a new object. – Mafii Jul 06 '18 at 10:53
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    @Mafii `.Distinct()` doesn't but `.Distinct().Count()` materializes the IEnumberable and creates a new object - I had a simmilar [question](https://stackoverflow.com/q/30366669/1315444) about that where you can see that `Distinct()` uses `Set<>` or `HashSet<>` internally – fubo Jul 06 '18 at 11:04
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    Oh, TIL. I'll take everything back then. Thank you! – Mafii Jul 06 '18 at 11:22