I resolved the problem in this way
string tfsIntegration = string.Format(string.Concat("http://localhost:49175"));
System.Net.XmlHttpRequest getProjectRequest = new System.Net.XmlHttpRequest();
getProjectRequest.Open("GET", tfsIntegration + "/GetProjects", false);
getProjectRequest.SetRequestHeader("Accept", "application/json");
getProjectRequest.SetRequestHeader("Content-Type", "application/json; charset=utf-8");
getProjectRequest.SetRequestHeader("X-HTTP-Method", "MERGE");
getProjectRequest.Send(null);