It doesn't send it by just setting the property, it apparently only sends after calling Response.Close(). But then the stream stays closed and the client can't send the body anymore. How do I send a HttpStatusCode.Continue response while still being able to read the request body and write a new response?
context.Response.StatusCode = (int)HttpStatusCode.Continue;
context.Response.KeepAlive = true;
context.Response.Close();
// cannot access disposed object!!
using (var body = context.Request.InputStream) {}