I was working on the integration between Dataverse and external Rest API. The scenario is simple as – “Send the JSON object to the API when the record is created”. In order to implement this, I decided to develop the plugin that will get the data from the context, transform it to the proper JSON object, and using HttpWebRequest/HttpWebResponse – perform the communication with the external API.

I built the console app in order to test that code works fine before moving the code to the plugin and it looked like the following:

var request = HttpWebRequest.Create("https://supersecret.api/api");
request.Method = "POST";
request.ContentType = "application/json";
request.Headers["Accept"] = "application/json";

var payloadObject = new PayloadObject();
//Setting properties of Payload Object here

var payloadObjectData = Serialize<PayloadObject>(payloadObject);

using (var sw = request.GetRequestStream())
{
    sw.Write(payloadObjectData, 0, payloadObjectData.Length);
    sw.Close();
}

string responseContent;

try
{
    using (var sr = new StreamReader(request.GetResponse().GetResponseStream()))
    {
        responseContent = sr.ReadToEnd();
    }

    var response = Deserialize<Response>(responseContent);
    //Handling of the response here
}
catch (WebException e)
{
    string errorMessage;

    using (var sr = new StreamReader(e.Response.GetResponseStream()))
    {
        errorMessage = sr.ReadToEnd();
    }

    //Handling of an error here
}

Code worked fine and did what it should with no issues. But when I moved this code to the plugin I immediately got “The ‘Accept’ header must be modified using the appropriate property or method. Parameter name: name” error during the first run. After a few experiments and variations of the code following change fixed the issue:

var request = (HttpWebRequest)HttpWebRequest.Create("https://supersecret.api/api");
request.Method = "POST";
request.ContentType = "application/json";
request.Accept = "application/json";