Get data from Monday.com using API using c#

How to pull data from monday.com using API in c#. I have tried the following code and it doesn’t work.

            var httpWebRequest1 = (HttpWebRequest)WebRequest.Create("https://api.monday.com/v2/");
            httpWebRequest1.ContentType = "application/json; charset=UTF-8";
            httpWebRequest1.Method = "GET";
            httpWebRequest1.Headers.Add("Authorization", "API Key");
            httpWebRequest1.GetResponse();
            var datapull = @"{""query"":""query {boards (ids: 1234) {name state items{id name column_values{text} }}}""";

             using (var streamWriter = new StreamWriter(httpWebRequest1.GetRequestStream()))
            {
                streamWriter.Write(datapull);
                Console.WriteLine(datapull);
            }

            var httpResponse1 = (HttpWebResponse)httpWebRequest1.GetResponse();

            using (var streamReader = new StreamReader(httpResponse1.GetResponseStream()))
            {
                var result = streamReader.ReadToEnd();
            }

I am encountering the following error when I used the code above.