I have retrieve a list of employees. my employee class columns(employeeId, lastname, genderid)

```
 List<m_employees> Items = new List<m_employees>
                    {
                        new m_employees{ employeeid = 1, lastname = "mike", genderid = 1 },
                        new m_employees{ employeeid = 2, lastname = "jeni", genderid = 2 }
                    };

```

then i have my gender class columns (id, title) 

```
    List<m_genders> genders = new List<m_genders>
                {
                    new m_genders{ id = 1, title = "Male" },
                    new m_genders{ id = 2, title = "Female" }
                };

//then i tried joining the retrieved list of employees to the genders

var x = from emp in Items
                    join sex in genders
                    on emp.genderid equals sex.id
                    into a from b in a.DefaultIfEmpty(new m_genders())
                    select new
                    {
                        emp.lastname,
                        emp.genderid,
                        sex = b.title
                    };

```

red error line is showing to the keyword join and says "the type of one of the expressions in the join clause is incorrect..."

how can i join them properly?