The cast to value type Int32 failed because the materialized value is null

Question

I have the following code  I m getting error        The cast to value type  Int32  failed because the materialized value is null  Either the result type s generic parameter or the query must use a nullable type      when CreditHistory table has no records   var creditsSum    from u in context User                   join ch in context CreditHistory on u ID equals ch UserID                                                           where u ID    userID                   select ch Amount  Sum      How can I modify the query to accept null values

User · Answer

I see that this question is already answered  But if you want it to be split into two statements  following may be considered   var credits   from u in context User               join ch in context CreditHistory                    on u ID equals ch UserID                                                       where u ID    userID               select ch   var creditSum  credits Sum x   gt   int  x Amount     0

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You are using aggregate function which not getting the items to perform action   you must verify linq query is giving some result as below   var maxOrderLevel  sdv Any    sdv Max s   gt  s nOrderLevel  0

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A linq-to-sql query isn t executed as code  but rather translated into SQL  Sometimes this is a  leaky abstraction  that yields unexpected behaviour    One such case is null handling  where there can be unexpected nulls in different places     DefaultIfEmpty 0  Sum 0  can help in this  quite simple  case  where there might be no elements and sql s SUM returns null whereas c  expect 0   A more general approach is to use    which will be translated to COALESCE whenever there is a risk that the generated SQL returns an unexpected null   var creditsSum    from u in context User               join ch in context CreditHistory on u ID equals ch UserID                                                       where u ID    userID               select  int  ch Amount  Sum      0    This first casts to int  to tell the C  compiler that this expression can indeed return null  even though Sum   returns an int  Then we use the normal    operator to handle the null case   Based on this answer  I wrote a blog post with details for both LINQ to SQL and LINQ to Entities

User · Answer

Had this error message when I was trying to select from a view   The problem was the view recently had gained some new null rows  in SubscriberId column   and it had not been updated in EDMX  EF database first    The column had to be Nullable type for it to work   var dealer   Context Dealers Where x    x dealerCode    dealerCode  FirstOrDefault     Before view refresh   public int SubscriberId   get  set      After view refresh   public Nullable lt int gt  SubscriberId   get  set      Deleting and adding the view back in EDMX worked   Hope it helps someone

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I have used this code and it responds correctly  only the output value is nullable   var packesCount   await botContext Sales Where s   gt  s CustomerId    cust CustomerId  amp  amp  s Validated                                   SumAsync s   gt   int  s PackesCount                               if packesCount    null                                                                   your code                                                           else                                                                  your code

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Got this error in Entity Framework 6 with this code at runtime   var fileEventsSum   db ImportInformations Sum x   gt  x FileEvents    Update from LeandroSoares   Use this for single execution   var fileEventsSum   db ImportInformations Sum x   gt   int  x FileEvents     0   Original   Changed to this and then it worked   var fileEventsSum   db ImportInformations Any     db ImportInformations Sum x   gt  x FileEvents    0

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I was also facing the same problem and solved through making column as nullable using     operator   Sequnce   db mstquestionbanks Where x   gt  x IsDeleted    false  amp  amp  x OrignalFormID    OriginalFormIDint  Select x  gt  lt b gt  int  x Sequence lt  b gt   Max   ToString      Sometimes null is returned

User · Answer

To allow a nullable Amount field  just use the null coalescing operator to convert nulls to 0   var creditsSum    from u in context User               join ch in context CreditHistory on u ID equals ch UserID                                                       where u ID    userID               select ch Amount    0  Sum

[c#] The cast to value type 'Int32' failed because the materialized value is null

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