WebClient Not Handling KeepAlive - Adding unwanted text to JSON body

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.NET

JSON

WebClient

Hey All,

I have a really strange issue that I can't seem to track down. I am posting small JSON objects to a webservice and getting back large JSON objects represented as strings. The problem I'm having is that randomly in the JSON object that is returned I get the following text:

DNT: 1 Connection: close

This obviously throws up when I try to deserialize the JSON. At first it was the Expect100-Continue in the body of the message, then it was the KeepAlive stuff and now it's the Connection: Close stuff. I am just using standard WebClient however I created a new class that inherits from WebClient so I can set the headers properly, here it is:

public class CustomWebClient : WebClient
{
    protected override WebRequest GetWebRequest(Uri address)
    {
        var request = base.GetWebRequest(address);
        if (request is HttpWebRequest)
        {
            (request as HttpWebRequest).KeepAlive = false;
            (request as HttpWebRequest).ServicePoint.Expect100Continue = false;
        }
        return request;
    }
}

and here is my implementation for the call:

using (var webClient = new CustomWebClient())
{
    webClient.Proxy = null;
    webClient.Headers[HttpRequestHeader.ContentType] = Constants.HttpJSONencodedHeader;

    return webClient.UploadData(request.Url, Constants.HttpPostVerb, Encoding.ASCII.GetBytes(request.Params.GetFormattedJSon()));
}

What I am expecting back is a JSON object that looks like this:

(simplified)

"276425": {
   "min": 1.0,
   "max": 1.0,
   "count": 1,
   "missing": 0,
   "distinctValues": [1],
   "countDistinct": 1,
   "sum": 1.0,
   "sumOfSquares": 1.0,
   "mean": 1.0,
   "stddev": 0.0,
   "facets": {}
}

This is what randomly comes back every now and then:

"280950": {
   "min": 1.0,
   "max": 1.0,
   "count": 1,
   "missing": 0,
   "distinctValues": [1],
   "countDistinct": 1,
   "sum": 1.
   DNT: 1
   Connection: close "stddev": 0.0,
   "facets": {}
}

the part to highlight is i have this right in the middle of the json object:

.
       DNT: 1
       Connection: close

Any and all help/suggestions would be greatly appreciated.