Use Linq to get Items in List that do not have a match in another list

Question

I have a list of employees, and a list of employeeGroups. I am trying get a list of employees that do not have a matching record in the employeeGroups list. I tried using the example found HERE but it is not working for my needs and I can't figure out how to change it to get the desired list. The result is always NULL.

Here is my code:

        List<ModuleView.EmployeeBO> employees = EmployeeBA.Employee_GetList_All(DB_Context, IsActiveChoice.Active, IsEnabledChoice.Enabled);
        List<PortalView.EmployeeGroupBO> groups = SecurityDA.EmployeeGroup_GetList_All(DB_Context);
        List<ModuleView.EmployeeBO> result = employees.Where(p2=> !groups.Any( p=>p.EmployeeId == p2.EmployeeId))  as List<ModuleView.EmployeeBO>;
        return result;

Any assistance is greatly appreciated!

score 2 · Accepted Answer · answered Nov 27 '17 at 16:45

2

The problem here is the as List<ModuleView.EmployeeBO>. The .Where() method always returns an IEnumerable<> that's lazily evaluated, not a List<>. To get this to work, simply change that to .ToList().

answered Nov 27 '17 at 16:45

Kyle Sletten

5,365
2
26
39

That was EXACTLY the problem. Thank you! – Rani Radcliff Nov 27 '17 at 16:49

score 0 · Answer 2 · answered Nov 27 '17 at 16:47

You might try this. I did not get a chance to test the code.

List<ModuleView.EmployeeBO> employees = EmployeeBA.Employee_GetList_All(DB_Context, IsActiveChoice.Active, IsEnabledChoice.Enabled);
List<PortalView.EmployeeGroupBO> groups = SecurityDA.EmployeeGroup_GetList_All(DB_Context);
List<ModuleView.EmployeeBO> result = employees.Where(p2=> !groups.Any( p=>p.EmployeeId == p2.EmployeeId)).ToList();
return result;

Use Linq to get Items in List that do not have a match in another list

2 Answers2