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Editorial Team
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Asked: 2026-05-21T17:58:58+00:00

I’m getting a report of errors from a production system. I don’t have easy

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I’m getting a report of errors from a production system. I don’t have easy access to the production system. I will get all the data that I need for it in due course, but what I’m trying to do is expedite the process of resolution of this issue. I’m trying to eliminate as much guesswork as possible.

The error I’m getting this this:

Extended Properties: Exception – System.InvalidOperationException: The
cast to value type ‘Decimal’ failed
because the materialized value is
null. Either the result type’s generic
parameter or the query must use a
nullable type.

The code where the error is happening is this:

IQueryable<AccountStatusModel> result = from d in Context.Debtors
    where // Condition here
    select new AccountStatusModel
    {
         // All of the below are decimal in the AccountStatusModel
         // and all of them are decimal NOT NULL in the database
         NotYetDue = d.sometable.dbcurrent,
         DueThisMonth = d.sometable.dbprd1bal,
         Overdue = d.sometable.dbprd2bal
                + d.sometable.dbprd3bal
                + d.sometable.dbprd4bal
                + d.sometable.dbprd5bal
                + d.sometable.dbprd6bal,
         PaymentRecievedNotAllocated = d.sometable.dbunalloc,
         OutstandingOrders = d.dmoutordval ?? 0,
         TotalBalance = d.sometable.dbcurrent
                + d.sometable.dbprd1bal
                + d.sometable.dbprd2bal
                + d.sometable.dbprd3bal
                + d.sometable.dbprd4bal
                + d.sometable.dbprd5bal
                + d.sometable.dbprd6bal
                + d.sometable.dbunalloc
                + (d.dmoutordval ?? 0),
         CreditLimit = d.dmcredlim,
         LastPayment = d.dmvallastpaid,

         // Some other properties here
         // ....
    };

Before someone comments on the field names, assume that these are fake names. =)
Note, that all the database fields being queried are NOT NULL.

I cannot reproduce this error in dev environment.

I think, that the reason this error happening in PROD, is because somehow, among the fields that are being queried, one is marked as NULL. I have no quick way of checking this, but I eventually will.

My question for now is this: Could there be any other reason for this error? Is it possible to get this error if the query is as above, and the fields are indeed NOT NULLs. (And why?) If it is possible could you please provide an example how.

Please only answer if you are positive that you are right, i.e. I need something stronger, than “I think this is so”.

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1 Answer

  1. Editorial Team

    So as I suspected in my comment to GregC answer, the problem was with a join. The schema turned out to be correct. However ever the query that I cited, can return nulls if “sometable” does not have a record for related “Debtors” record. I this case d.sometable.Anything will be null. Because L2E coalesces NULLS it does not complain that d.sometable is null simply returning null for d.sometable.Anything instead.

    So this how and why.

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