The code below works unless p.School.SchoolName turns out to be null, in which case it results in a NullReferenceException.

if (ExistingUsers.Where(p => p.StudentID == item.StaffID &&
                        p.School.SchoolName == item.SchoolID).Count() > 0)
{
    // Do stuff.
}

ExistingUsers is a list of users:

public List<User> ExistingUsers;

Here is the relevant portion of the stacktrace:

System.NullReferenceException: Object reference not set to an instance of an object.

at System.Linq.Enumerable.WhereListIterator1.MoveNext()
at System.Linq.Enumerable.Count[TSource](IEnumerable1 source)

How should I handle this where clause?

Thanks very much in advance.