linq - How to find Difference in two Collections<T> in C# -

i have 2 collections of following class

public class abc {    public int studentid {get;set;}    public int schoolid {get;set;}    // class has other properties both above 2 keys  } 

now have 2 collections of abc

  icollection<abc> c1 = {some data}   icollection<abc> c2 = {some data} 

i want find objects of abc in c1 not in c2 based on keys i-e studentid , schoolid

use except

var diff = c1.except(c2) 

please note, in order track equality can override equals method, or implement , pass iequalitycomparer except method

class abcequalitycomparer : iequalitycomparer<abc> {     public bool equals(abc b1, abc b2)     {          return (b1.studentid == b2.studentid) && (b1.schoolid == b2.schoolid)     }      public int gethashcode(abc b)     {         return 7*b.studentid.gethashcode() + b.schoolid.gethashcode();     } } 

than can use

var diff = c1.except(c2, new abcequalitycomparer())