If you want to get the count of users created each month of specified year, use:
var years = context.Profiles
.Select(u=>u.CreatedOn.Year)
.Distinct()
.ToList();
ComboBox1.DataSource = years;
int uyear = 2014;
var qry = context.Profiles
.Where(u=>u.CreatedOn.Year == uyear)
.GroupBy(u=> u.CreatedOn.Month)
.Select(grp=>new{month=grp.Key, count=grp.Count()})
.ToList();
Good luck!