Add an HTTP header more than once and send it separately using HttpWebRequest

Question

I need to send more than a Set-Cookie HTTP header using HttpWebRequest class.

Problem is first request.Headers.Add("Set-Cookie", "[cookie string]") adds the header as expected, but subsequent ones are concatenated in the first added header.

Default behavior complicates obtaning a set of cookies by the receiver of a given request, because isn't that easy split the header again in separate cookies' strings.

Is there any way of adding n times some header?

Perhaps some headers mustn't be repeated, but Set-Cookie is a valid use case, because receiver should read more than a cookie.

Thank you.

Matías Fidemraizer · Accepted Answer · 2011-12-13 13:38:54Z

After spending some time looking for an out-of-the-box solution, I ended implementing an extension method to System.Net.WebHeaderCollection:

public static class WebHeaderCollectionExtensions
{
    public static ILookup<string, string> ToLookup(this WebHeaderCollection some)
    {
        List<KeyValuePair<string, string>> headers = new List<KeyValuePair<string, string>>();

        if (some.Count > 0)
        {
            string[] tempSplittedHeaders = null;

            foreach (string headerName in some)
            {
                if (some[headerName].Contains(";,"))
                {
                    tempSplittedHeaders = Regex.Split(some[headerName], ";,");

                    foreach (string splittedHeader in tempSplittedHeaders)
                    {
                        headers.Add(new KeyValuePair<string, string>(headerName, splittedHeader));
                    }
                }
                else
                {
                    headers.Add(new KeyValuePair<string, string>(headerName, some[headerName]));
                }
            }
        }

        return headers.ToLookup(keySelector => keySelector.Key, elementSelector => elementSelector.Value);
    }
}

Thanks to this wonderful extension method, I'm able to convert headers' collection to a lookup, which allows duplicate keys, and at the end of the day, doing some processing, I get a list of all HTTP headers in separately:

string wholeCookie = WebOperationContext.Current.IncomingRequest.Headers.ToLookup()["Set-Cookie"].Single(cookie => cookie.Contains("[Cookie name]"));

I hope sharing my solution will be a good contribution, as I guess others had or are having a similar case use!

If it comes to cookies, I believe that HttpWebRequest.CookieContainer property is what you were looking for, some more reading here: msdn.microsoft.com/en-us/library/dd920298(v=vs.95).aspx

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