Intermittent error with EF Core: The connection does not support MultipleActiveResultSets

Question

I have an ASP.Net Core application that uses EF Core.

I use ASP.Net Identity and share the same DBContext for my app's entities.

I have set my connection string to an Azure SQL database to have MultipleActiveResultSet=True.

It works for a day or two, but eventually it fails with the error:

The connection does not support MultipleActiveResultSets.

I don't think MARS is the real issue since it worked for the first two days it was up.

I am using ASP.Net Core's built-in DI to set my DbContext.

services.AddDbContext<AppDbContext>(options =>
  options.UseSqlServer(appDbContextConnectionString));

My understanding is that the default lifetime for the DbContext above is Transient (per web request).

Is it alright to share the same DBContext with ASP.Net Identity or should I have a separate one for my app's entities, pointed to the same DB?

I don't know if this is an issue with EF Core, ASP.Net Core or with SQL Azure configuration.

Solution 1

I had a similar issue and I found that the problem was that I missed an await statement in front of my method.

FetchStuffFromDBAsync();

Became:

await FetchStuffFromDBAsync();

And the problem was gone.

Solution 2

MultipleActiveResultSets=True need to add in connection string.

string connectionString = "Data Source=MSSQL1;Initial Catalog=AdventureWorks;Integrated Security=SSPI;MultipleActiveResultSets=True"; 

Solution 3

Multiple Active Result Sets (MARS) is a feature that works with SQL Server to allow the execution of multiple batches on a single connection. When MARS is enabled for use with SQL Server, each command object used adds a session to the connection.

The MARS feature is disabled by default.

You can enable it like below.

string connectionString = "Data Source=MSSQL1;" +   
    "Initial Catalog=AdventureWorks;Integrated Security=SSPI;" +  
    "MultipleActiveResultSets=True";  

Special Considerations When Using MARS

Comments

[A.J.Bauer]

You might want to check if your connection string with "MultipleActiveResultSet=True" is actually used at runtime. Just a guess. stackoverflow.com/questions/12690453/…

[slasky]

Can you please explain why?

[JvR]

Can you give more info on why it needs to be added though? Especially if it's intermittent and a new transient connection is created per request anyway