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SQL Server Compact Edition 4 - AccessViolationException

I am building a .NET 4 WPF application using Entity Framework code and SQL Server Compact 4.0. I try to call DbContext.SaveChanges()in the background thread to avoid blocking the user interface, but sometimes I get the following exception:

System.AccessViolationException occurred
  Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
  Source=System.Data.SqlServerCe
  StackTrace:
       at System.Data.SqlServerCe.NativeMethodsHelper.OpenStore(IntPtr pOpenInfo, IntPtr pfnOnFlushFailure, IntPtr& pStoreService, IntPtr& pStoreServer, IntPtr& pQpServices, IntPtr& pSeStore, IntPtr& pTx, IntPtr& pQpDatabase, IntPtr& pQpSession, IntPtr& pStoreEvents, IntPtr& pError)
       at System.Data.SqlServerCe.NativeMethods.OpenStore(IntPtr pOpenInfo, IntPtr pfnOnFlushFailure, IntPtr& pStoreService, IntPtr& pStoreServer, IntPtr& pQpServices, IntPtr& pSeStore, IntPtr& pTx, IntPtr& pQpDatabase, IntPtr& pQpSession, IntPtr& pStoreEvents, IntPtr& pError)
       at System.Data.SqlServerCe.SqlCeConnection.Open(Boolean silent)
       at System.Data.SqlServerCe.SqlCeConnection.Open()
       at System.Data.EntityClient.EntityConnection.OpenStoreConnectionIf(Boolean openCondition, DbConnection storeConnectionToOpen, DbConnection originalConnection, String exceptionCode, String attemptedOperation, Boolean& closeStoreConnectionOnFailure)
       at System.Data.EntityClient.EntityConnection.Open()
       at System.Data.Objects.ObjectContext.EnsureConnection()
       at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
       at System.Data.Entity.Internal.InternalContext.SaveChanges()
       at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
       at System.Data.Entity.DbContext.SaveChanges()
       at SourceLog.Model.LogSubscriptionManager.<SaveChanges>b__2() in C:\github.com\tomhunter-gh\SourceLog\SourceLog.Model\LogSubscriptionManager.cs:line 51
  InnerException: (null)

Here is the code that calls SaveChanges():

internal static readonly object DbSaveLockObject = new object();
public static void SaveChanges()
{
    Task.Factory.StartNew(() =>
    {
        lock (DbSaveLockObject)
        {
            Debug.WriteLine(DateTime.Now + ": SaveChanges in lock");
            Db.SaveChanges();
        }
    });
}
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2 answers

The problem here is not in serializing access to the DbContext object, which avoids access to the same object from different threads. So the solution is to ensure that a new DbContext is created every time you need to interact with the database.

using (var db = new SourceLogContext())
{
    db.LogSubscriptions.First(s => s.LogSubscriptionId == LogSubscriptionId)
        .Log.Add((LogEntry)e.LogEntry);
    db.SaveChanges();
}

, . , LogSubscription.Log, , .

_uiThread.Post(entry => Log.Add((LogEntry)entry), e.LogEntry);

- , , . , , DbContext .

private static readonly SourceLogContext DbUILazyLoadContext = new SourceLogContext();

.

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