c# - OutOfMemoryException: using DbContext in Task -

this following setup i'm dealing with:

• i got sql-table ~1.000.000 entries need update
• the update takes place in seperate thread (started task)
• as memory limited in thread, process list in batches of 1000 entries per batch (when running in test-project in mainthread/without task, there no oom exception)
• the updatelist() function either updates fields of list or creates new record or other tables in dbcontext
• in process_failure() function, have single context instance entire list
• in process_success() function, moved while-loop outside of context

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private void process_success() {     var totalprocessedcounter = 0;      while( true )     {         using( var context = new mydbcontext() )         {             var list = context.myclass.orderby( x => x.id )                 .skip( totalprocessedcounter ).take( 1000 )                 .tolist();              if( !list.any() )                 break;              updatelist( list );              totalprocessedcounter += list.count;         }     } }  private void process_failure() {     var totalprocessedcounter = 0;      using( var context = new mydbcontext() )     {         while( true )         {             var list = context.myclass.orderby( x => x.id )                 .skip( totalprocessedcounter ).take( 1000 )                 .tolist(); // throws outofmemoryexception              if( !list.any() )                 break;              updatelist( list );              totalprocessedcounter += list.count;         }     } }  private void updatelist( list<myclass> list ) {     var dosavechanges = false;      list = list.where( x => somefilter( x ) ).tolist();      using( var context = new mydbcontext() )     {         foreach( var item in list )         {             changeitem( item );         }          if( dosavechanges )             context.savechanges();     } } 

gets context somehow polluted/filled when create instance in nested functioncall of updatelist()?

the reason why exception because dbcontext caches the data read db, therefore @ point blow memory if keep adding entities cache , outofmemoryexception. entities not cleared gc because being referenced dbcontext.

try using .asnotracking():

private void process_notracking() {     var totalprocessedcounter = 0;      using( var context = new mydbcontext() )     {         while( true )         {             var list = context                           .myclass                           .asnotracking()                           .orderby( x => x.id )                           .skip( totalprocessedcounter )                           .take( 1000 )                           .tolist();               if( !list.any() )                 break;              updatelist( list );              totalprocessedcounter += list.count;         }     } } 

but if not track entities, updating them is more difficult (read "attaching existing entity context"), because entities not belong context , not being tracked.

i not use ef somethng this, looks mission update/select sql statement.