How to force IIS to send response headers without sending response body and closing connection

I am trying to stream dynamically generated data to a client over HTTP using IIS, and the connection has to remain open for a long period of time, and the server will send periodic status updates to the client while it is performi开发者_如何学JAVAng a time-consuming operation.

This MUST all be handled within ONE request, but I am using a WebClient.OpenRead() stream, which cannot be opened until the headers are sent.

How can I force IIS to send headers to the client, and later send a response body?

This behaviour is normally achievable by setting KeepAlive to true and setting Expect header to "100 and continue". By doing this, server will send the headers with result code 100.

I am not sure if this is possible using WebClient.

Use HttpWebRequest instead to be able to set the values above. In fact WebClient does nothing magical but using GET to get the data. Here is the code for calling OpenRead in Reflector:

try
    {
        request = this.m_WebRequest = this.GetWebRequest(this.GetUri(address));
        Stream responseStream = (this.m_WebResponse = this.GetWebResponse(request)).GetResponseStream();
        if (Logging.On)
        {
            Logging.Exit(Logging.Web, this, "OpenRead", responseStream);
        }
        stream2 = responseStream;
    }
    catch (Exception exception)
    {
     //