The CancellationToken in a TaskCanceledException on ToListAsync does not match

[JakobFerdinand]

Why does the TaskCanceledException to be the given one but it isn´t

using (MyDbContext dbContext = new())
{
    CancellationTokenSource cts = new();
    cts.Cancel();

    try
    {
        await dbContext.People.ToListAsync(cts.Token);
    }
    catch (TaskCanceledException ex) when (ex.CancellationToken == cts.Token) // that is what I´m expecting
    {
        Console.WriteLine("No problem"); 
    }
    catch (TaskCanceledException ex) when (ex.CancellationToken == CancellationToken.None) // that is what is happening
    {
        Console.WriteLine("Why?");
    }
}

Can you explain the given cts.Token is not passed to the exception?

provider and version information

EF Core version: 7.0.5
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 7.0
Operating system: Windows 11
IDE: Visual Studio 2022 17.5

[roji]

This is a bug in the SqlClient low-level driver; the same code works when using PostgreSQL.

[JRahnama]

@JakobFerdinand Can you include a simple repro that does not use EFCore and reproduce the issue?

[roji]

@JRahnama here you go; the following code prints False with SqlClient, but True with e.g. Npgsql.

Note that this specifically tests for passing an already-cancelled token to a SqlClient call. There are other paths where the token is cancelled only after the operation already started - these also need to throw an exception containing the token. Basically wherever you're creating an OperationCanceledException/TaskCanceledException, the triggering token should be passed in.

await using var connection = new SqlConnection("Server=localhost;Database=test;User=SA;Password=Abcd5678;Connect Timeout=60;ConnectRetryCount=0;Encrypt=false");
await connection.OpenAsync();

var cancelledToken = new CancellationToken(canceled: true);
await using var command = new SqlCommand("SELECT 1", connection);

try
{
    await command.ExecuteReaderAsync(cancelledToken);
}
catch (OperationCanceledException e)
{
    Console.WriteLine($"Token on exception matches: {e.CancellationToken == cancelledToken}");
}

[samsharma2700]

This issue is on our radar and related to this #26 . We will evaluate internally and update.