linq - Implementing IEqualityComparer<T> on an object with two properties in C# -

i have case need grab bunch of items on distinct, source collection of objects 2 properties, this:

public class skillrequirement {     public string skill { get; set; }     public string requirement { get; set; } } 

i try collection follows:

skillrequirementcomparer scom = new skillrequirementcomparer();  var distinct_list = source.distinct(scom); 

i tried implement iequalitycomparer<t> this, fell stumped @ gethashcode() method.

the class comparer:

public class skillrequirementcomparer : iequalitycomparer<skillrequirement> {     public bool equals(skillrequirement x, skillrequirement y)     {         if (x.skill.equals(y.skill) && x.requirement.equals(y.requirement))         {             return true;         }         else         {             return false;         }     }      public int gethashcode(skillrequirement obj)     {         //?????     } } 

normally use gethashcode() on property, because comparing on 2 properties, i'm bit @ loss of do. doing wrong, or missing obvious?

you can implement gethashcode in following way:

public int gethashcode(skillrequirement obj) {     unchecked     {         int hash = 17;         hash = hash * 23 + obj.skill.gethashcode();         hash = hash * 23 + obj.requirement.gethashcode();         return hash;     } } 

_{originally j.skeet}

if properties can null should avoid nullreferenceexception, e.g.:

int hash = 17; hash = hash * 23 + (obj.skill ?? "").gethashcode(); hash = hash * 23 + (obj.requirement ?? "").gethashcode(); return hash;