support added for restsharp#781: ability to set HttpHeader 'Connectio…

…n' to 'keep-alive' or 'close' using the existing header dictionary

RestSharp/Http.Sync.cs

@@ -139,7 +139,13 @@ private HttpResponse PostPutInternal(string method)
 
         partial void AddSyncHeaderActions()
         {
-            this.restrictedHeaderActions.Add("Connection", (r, v) => r.Connection = v);
+            //this.restrictedHeaderActions.Add("Connection", (r, v) => r.Connection = v);
+            this.restrictedHeaderActions.Add("Connection", (r, v) => {
+                if (v.ToLower().Contains("keep-alive"))
+                    r.KeepAlive = true; //if a user sets the connection header explicitly to "keep-alive" then we set the field on HttpWebRequest
+                else
+                    r.KeepAlive = false; //if "Connection" is specified as anything else, we turn off keep alive functions
+            });
             this.restrictedHeaderActions.Add("Content-Length", (r, v) => r.ContentLength = Convert.ToInt64(v));
             this.restrictedHeaderActions.Add("Expect", (r, v) => r.Expect = v);
             this.restrictedHeaderActions.Add("If-Modified-Since", (r, v) => r.IfModifiedSince = Convert.ToDateTime(v));