Server-Sent Events (sse) sample as minimal API in ASP

server-sent-event-sample.cs

app.MapGet("/sse/connect", async (HttpContext context, CancellationToken ct) => {
    context.Response.Headers.Append("Content-Type", "text/event-stream");
    context.Response.Headers.Append("Cache-Control", "no-cache");
    context.Response.Headers.Append("Connection", "keep-alive");

    var result = new SSEResult();
    for (var i = 0; i < 10; i++) {
        if (ct.IsCancellationRequested) return;
        result.DateTime = DateTime.Now;

        await context.Response.WriteAsync("data:", cancellationToken: ct);
        await JsonSerializer.SerializeAsync(context.Response.Body, result, cancellationToken: ct);
        await context.Response.WriteAsync("\n\n", cancellationToken: ct);
        await context.Response.Body.FlushAsync(ct); //ensures that the data is sent immediately.

        await Task.Delay(1000, ct);
    }
});