Linq generic parameter error

Question

I know why this is happening but can somebody help me in the right direction of syntax? Currently I have three tables joined by one to one optional relationship. And I joined them as left outer join. My query is....

var model = from t1 in db.Doctors
            join d in db.DoctorAddress on t1.DoctorId equals  d.DoctorId into listi
            join dc in db.DoctorCharges on t1.DoctorId equals dc.DoctorId into listj
            join da in db.DoctorAvailablities on t1.DoctorId equals da.DoctorId into listk
            from d in listi.DefaultIfEmpty()
            from dc in listj.DefaultIfEmpty()
            from da in listk.DefaultIfEmpty()
            select new
            {
                Name = t1.Name,
                RoomNo = da.RoomNo,
                IPDCharge = dc.OPDCharge,
                Address = d.Address,
            };

My problem is that OPDCharge is of type Decimal(not null)

The error I get is:

Exception Details: System.InvalidOperationException: The cast to value type 'Double' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.

What would be the correct syntax?

What datatypes are dc.OPDCharge and IPDCharge? Also what is the datatype of the column in the database? — gunr2171
– gunr2171, Commented Aug 14, 2013 at 15:48

Magnus · Accepted Answer · 2013-08-14 15:50:30Z

1

I think an explicit cast to a nullable should do it:

IPDCharge = (decimal?)dc.OPDCharge

But the error message suggest that the type of OPDCharge is actually double, so maybe cast to double? instead?

answered Aug 14, 2013 at 15:50

Magnus

47.5k8 gold badges88 silver badges129 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Magnus Over a year ago

@gunr2171 but IPDCharge is in an anonymous type an has the same type as the target.

stevepkr84 · Accepted Answer · 2013-08-14 15:51:44Z

1

If you want to accept null as being 0 then try:

IPDCharge = dc.OPDCharge ?? 0;

More info: http://msdn.microsoft.com/en-us/library/ms173224.aspx

answered Aug 14, 2013 at 15:51

stevepkr84

1,6672 gold badges13 silver badges23 bronze badges

Comments

Alessandro D'Andria · Accepted Answer · 2013-08-14 15:50:33Z

0

Try with

IPDCharge = dc.OPDCharge.GetValueOrDefault(0)

answered Aug 14, 2013 at 15:50

Alessandro D'Andria

8,8882 gold badges39 silver badges33 bronze badges

Collectives™ on Stack Overflow

Linq generic parameter error

3 Answers 3

1 Comment

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Related