EF other way to Sum() new Column - entity-framework

Question

i got stuck on this query that calculate the new column.
i cannot explain briefly just see the snippet code below.
from user in context.Table
select new
{
Total = user.Total,
Paid = user.Paid,
Balance = //should be Total - Paid to assign result
}
i have tried this query
var result = from a in context.EnrollmentRequests
where a.SchoolYear == SchoolYear
select new
{
a.StudentID,
Name = a.Student.FirstName + " " + a.Student.MiddleName + " " + a.Student.LastName,
Tuition = context.Miscs.Where(m => m.YearLevel == a.YearLevel && m.SchoolYear == SchoolYear && m.Term == a.Term && m.CourseID == a.CourseID)
.Select(ms => new { Amount = ms.Amount })
.Union(context.StudentCharges
.Where(s => s.YearLevel == a.YearLevel && s.SchoolYear == SchoolYear && s.Term == a.Term && s.CourseID == a.CourseID && s.StudentID == a.StudentID)
.Select(ss => new { Amount = ss.Amount }))
.Union(context.StudentSubjectTakes
.Where(st => st.StudentID == a.StudentID && st.SchoolYear == a.SchoolYear && st.Term == a.Term && st.YearLevel == a.YearLevel && st.EducationalLevel == a.Student.StudentAdvanceEducations.FirstOrDefault().EducationLevel)
.Select(st => new
{
Amount = context.SubjectOfferedFees
.Where(f => f.SubjectsOfferedID == st.SubjectsOfferedID).Sum(w => (decimal?)w.Cost ?? 0)
}))
.Select(f => f.Amount).Sum(),
PaymentMade = context.Payments.Where(p => p.SchoolYear == SchoolYear && p.Term == a.Term && p.StudentID == a.StudentID && p.PaymentDes == "Tuition Fee").Sum(sm => (decimal?)sm.Amount),
Balance = Tuition - PaymentMade //Does not exist on current context
};
but doesn't work it says that does not exist on current context.
how could this possible.
thanks. this will be helpful to anyone.

Answer 1

Balance = user.Total - user.Paid