How to find the difference between 2 IEnumerable objects

Question

I have 2 list of guids as:

IEnumerable<dynamic> userids = null;
IEnumerable<dynamic> lsCheckedUsers = null;

The userids and lsCheckedUsers list are populated from a SQL database using dapper.

I now wish to find all userids that are not in lsCheckedUsers.

I have tried the following

var userdifference = userids.Where(i => !lsCheckedUsers.Contains(lsCheckedUsers));
var userdifference = userids.Except(lsCheckedUsers);

None of the above actual returns the difference between the 2.

How do I get the difference of guids that do not exist in both.

I am certain that lsCheckedUsers has Guids that are in userids

Answer 1

This is correct:

var userdifference = userids.Except(lsCheckedUsers);

It will work if both of your IEnumerable<dynamic> actually contain Guids. Print out or inspect the items in each to make sure they are Guids.

You should really be using IEnumerable<Guid> and cast the incoming items to Guids if this is what you are expecting. It will hopefully prevent errors like the one you are potentially seeing.

Answer 2

Something along those lines..

var difference = list1.Where (e => !list2.Any(a => a == e))