How to cancel Net Core 6.0 web API request when Client aborted?

Question

I am trying to cancel a long-running action on the server side when the client cancels or aborts the request. I am using ASP.Net Core 6.0 and the fetch API with Signal. HttpContext.RequestAborted.IsCancellationRequested is always false.

while (true)
{
   CancellationToken cancellationToken = HttpContext.RequestAborted;

   if (cancellationToken.IsCancellationRequested)
   {
      tokenSource2.Cancel();
   }
}

Answer 1

You can add a CancellationToken to your action and pass it down to your long-running task:

[HttpGet("slow")]
public async Task<string> Get(CancellationToken cancellationToken)
{
    // Your slow action
    var result = await CalculateResultAsync(10000, cancellationToken);

    return result;
}

And in your long-running task:

public async Task<string> CalculateResultAsync(int input, CancellationToken cancellationToken)
{
    for(var i = 0; i < input; i++)
    {
        cancellationToken.ThrowIfCancellationRequested();

        await Task.Delay(1000);
    }

    return "Finished!";
}