NpgsqlTransaction.CheckDisposed throwing exception

Steps to reproduce

-> Initialize DbContext without using explicit transaction -> Calling SaveChanges will throw a ObjectDisposedException by name NpgsqlTransaction

The issue

Hello.

I’m trying to run the SaveChanges method with Entity Framework 6 but after updating Npgsql to version 5 an exception is thrown.

The curious thing is that when using transaction control manually, the exception is not thrown by Npgsql.

Could you please check.

Thanks

---

this code does not work

public async Task ActivateUser(int idUser, CancellationToken token = default) {
    using var ctx = new PContexto();
    try {
        var usr = await ctx.Users.FindAsync(token, idUser);

        if (usr == null) {
            throw new Exception("User not found.");
        }

        usr.Active = true;

       //exception is thrown here, but only after the commit is complete
        await ctx.SaveChangesAsync(token);
    }
    catch {
        throw;
    }
}

this code works

public async Task ActivateUser(int idUser, CancellationToken token = default) {
    using var ctx = new PContexto();
    using var t = ctx.Database.BeginTransaction();
    try {
        var usr = await ctx.User.FindAsync(token, idUser);

        if (usr == null) {
            throw new Exception("User not found");
        }

        usr.Active = true;

        await ctx.SaveChangesAsync(token);

        t.Commit();
    }
    catch {
        t.Rollback();
        throw;
    }
}

---

Entity Log:

Opened connection asynchronously at 27/04/2021 18:12:33 -03:00

Started transaction at 27/04/2021 18:12:33 -03:00

UPDATE “sis”.“table_name” SET “field”=@p_0 WHERE “id” = @p_1

– p_0: ‘False’ (Type = Boolean, IsNullable = false)

– p_1: ‘999’ (Type = Int32, IsNullable = false)

– Executing asynchronously at 27/04/2021 18:12:33 -03:00

– Completed in 5 ms with result: 1

Committed transaction at 27/04/2021 18:12:33 -03:00

Closed connection at 27/04/2021 18:12:33 -03:00

Exception thrown: ‘System.ObjectDisposedException’ in mscorlib.dll

---

Exception message:

It is not possible to access a discarded object. Object name: ‘NpgsqlTransaction’.

Stack trace:

   at Npgsql.NpgsqlTransaction.CheckDisposed()
   at Npgsql.NpgsqlTransaction.get_Connection()
   at Npgsql.NpgsqlTransaction.get_DbConnection()
   at System.Data.Common.DbTransaction.get_Connection()
   at System.Data.Entity.Infrastructure.Interception.DbTransactionDispatcher.Dispose(DbTransaction transaction, DbInterceptionContext interceptionContext)
   at System.Data.Entity.Core.EntityClient.EntityTransaction.Dispose(Boolean disposing)
   at System.Data.Common.DbTransaction.Dispose()
   at System.Data.Entity.Core.Objects.ObjectContext.<ExecuteInTransactionAsync>d__156`1.MoveNext()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.Core.Objects.ObjectContext.<SaveChangesToStoreAsync>d__154.MoveNext()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.Core.Objects.ObjectContext.<SaveChangesInternalAsync>d__151.MoveNext()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Opm.Data.Utils.Repositorio.RepositorioBase`2.<UpdateAsync>d__32.MoveNext() in D:\Sources\Extensions\OP.Data.Utils\Repositorio\RepositorioBase.cs:line 650

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Further technical details

Npgsql version: 5.0.4.0 PostgreSQL version: 13.0 Operating system: CentOS 8

[vonzshik]

The problem is with unbinding of the transaction - with the pooled connection we unbind it every time a connection is returned to the pool, but we do not do the same for the unpooled ones.

[roji]

Thanks @tnering. In general, the EF6 provider is pretty much “archived” and we don’t test it with newer versions of Npgsql; so my recommendation would be to not necessarily upgrade that, unless you have a very specific problem you’re looking to solve. I’m mainly interested in case it exposes a bug in Npgsql itself.