The operation cannot be completed because the DbContext has been disposed error

Question

I m new to EF and I m trying to use an extension method which converts from my Database type User to my info class UserInfo  I m using database first if that makes a difference   My code below gives the error      The operation cannot be completed because the DbContext has been disposed    try       IQueryable lt User gt  users      using  var dataContext   new dataContext                  users   dataContext Users                    Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false           if users Any      false                        return null                      return users Select x   gt  x ToInfo    ToList       this line is the problem   catch  Exception ex                  I can see why it would do it  but I also don t understand why the result of the where statement isn t being saved into the users object   So I guess my main question is why doesn t it work and secondly what s the right way of using extension methods and EF

User · Answer

using var database new DatabaseEntities        Don t use using statement  Just write like that  DatabaseEntities database new DatabaseEntities         It will work     For documentation on the using statement see here

User · Answer

This can be as simple as adding ToList   in your repository  For example   public IEnumerable lt MyObject gt  GetMyObjectsForId string id        using  var ctxt   new RcContext                     causes an error         return ctxt MyObjects Where x   gt  x MyObjects Id    id             Will yield the Db Context disposed error in the calling class but this can be resolved by explicitly exercising the enumeration by adding ToList   on the LINQ operation   public IEnumerable lt MyObject gt  GetMyObjectsForId string id        using  var ctxt   new RcContext                  return ctxt MyObjects Where x   gt  x MyObjects Id    id  ToList

User · Answer

You need to remember that IQueryable queries are not actually executed against the data store until you enumerate them     using  var dataContext   new dataContext        This line of code doesn t actually do anything other than build the SQL statement      users   dataContext Users Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false      Any   is an operation that enumerates the IQueryable  so the SQL is sent to the data source  through dataContext   and then the  Any   operations is executed against it      if users Any      false                return null            Your  problem  line is reusing the sql built above  and then doing an additional operation   Select     which just adds to the query   If you left it here  no exception  except your problem line  return users Select x   gt  x ToInfo    ToList       this line is the problem   calls  ToList    which enumerates the IQueryable  which causes the SQL to be sent to the datasource through the dataContext that was used in the original LINQ query   Since this dataContext has been disposed  it is no longer valid  and  ToList   throws an exception   That is the  why it doesn t work    The fix is to move this line of code inside the scope of your dataContext   How to use it properly is another question with a few arguably correct answers that depend on your application  Forms vs  ASP net vs  MVC  etc     The pattern that this implements is the Unit of Work pattern   There is almost no cost to creating a new context object  so the general rule is to create one  do your work  and then dispose of it   In web apps  some people will create a Context per request

User · Answer

The reason why it is throwing the error is the object is disposed and after that we are trying to access the table values through the object  but object is disposed Better to convert that into ToList   so that we can have values  Maybe it isn t actually getting the data until you use it  it is lazy loading   so dataContext doesn t exist when you are trying to do the work  I bet if you did the ToList   in scope it would be ok   try       IQueryable lt User gt  users      var ret   null       using  var dataContext   new dataContext                  users   dataContext Users Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false            if users Any                          ret   users Select x   gt  x ToInfo    ToList                           Return ret    catch  Exception ex

User · Answer

Objects exposed as IQueryable lt T gt  and IEnumerable lt T gt  don t actually  execute  until they are iterated over or otherwise accessed  such as being composed into a List lt T gt   When EF returns an IQueryable lt T gt  it is essentially just composing something capable of retrieving data  it isn t actually performing the retrieve until you consume it   You can get a feel for this by putting a breakpoint where the IQueryable is defined  vs  when the  ToList   is called   From inside the scope of the data context as Jofry has correctly pointed out   The work to pull the data is done during the ToList   call   Because of that  you need to keep the IQueryable lt T gt  within the scope of the data context

User · Answer

Change this   using  var dataContext   new dataContext          users   dataContext Users Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false        if users Any                  ret   users Select x   gt  x ToInfo    ToList                 to this   using  var dataContext   new dataContext          return   dataContext Users Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false  Select x   gt  x ToInfo    ToList         The gist is that you only want to force the enumeration of the context dataset once  Let the caller deal with empty set scenario  as they should

User · Answer

Here you are trying to execute IQueryable object on inactive DBContext  your DBcontext is already disposed of  you can only execute IQueryable object before DBContext is disposed of  Means you need to write users Select x   gt  x ToInfo    ToList   statement inside using scope

User · Answer

This question  amp  answer lead me to believe that IQueryable require an active context for its operation  That means you should try this instead   try       IQueryable lt User gt  users       using  var dataContext   new dataContext                  users   dataContext Users Where x   gt  x AccountID    accountId  amp  amp  x IsAdmin    false            if users Any      false                        return null                    else                       return users Select x   gt  x ToInfo    ToList       this line is the problem                     catch  Exception ex

[c#] The operation cannot be completed because the DbContext has been disposed error

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