c# - How to validate if a collection contains all unique objects -

i have c# collection of objects not implement iequatable or icomparable. want check if collection contains duplicate objects. i.e. want know if object.referenceequals(x, y) false x , y in list.

how efficiently?

it nice both c# , linq method.

non-linq, when collection implements icollection<t> or icollection:

bool allitemsunique =     new hashset<yourtype>(yourcollection).count == yourcollection.count; 

non-linq, when collection doesn't implement icollection<t> or icollection. (this version has better theoretical performance first because break out duplicate found.)

bool allitemsunique = true;  var tempset = new hashset<yourtype>(); foreach (yourtype obj in yourcollection) {     if (!tempset.add(obj))     {         allitemsunique = false;         break;     } } 

linq. (this version's best case performance -- when collection implements icollection<t> or icollection -- same first non-linq solution. if collection doesn't implement icollection<t> or icollection linq version less efficient.)

bool allitemsunique =     yourcollection.distinct().count() == yourcollection.count();