Share post on linkdin , instagram , Facebook

Hi i want to post message on linkdin,Facebbok and Instagram using asp.net C# / MVC Application
 
I have tried many articles but didnot find any solution, please help me that how can i perform such task,
 
please share if anyone have used such implementation 

 private string linkedinSharesEndPoint = "https://api.linkedin.com/v1/people/~/shares?oauth2_access_token={0}";
        private const string defaultUrl = "https://www.linkedin.com/in/futuresoft-india-b9b1931bb/";
        private const string defaultImageUrl = "some-image-url";
        string accessToken = "";
        string title = "Post Test";
        protected void Page_Load(object sender, EventArgs e)
        {
            bool r= PostLinkedInNetworkUpdate( accessToken,  title,  defaultUrl, defaultImageUrl);
          if(r)
            {
                string s = "sucess";
            }
        }
       

        public bool PostLinkedInNetworkUpdate(string accessToken, string title, string submittedUrl = defaultUrl, string submittedImageUrl = defaultImageUrl)
        {
           

            var requestUrl = String.Format(linkedinSharesEndPoint, accessToken);
            var message = new
            {
                comment = "Testing out the LinkedIn Share API with JSON",
                content = new Dictionary<string, string>
        { { "title", title },
            { "submitted-url", submittedUrl },
            {"submitted-image-url" , submittedImageUrl}
        },
                visibility = new
                {
                    code = "anyone"
                }
            };

            var requestJson = new JavaScriptSerializer().Serialize(message);

            var client = new WebClient();
            var requestHeaders = new NameValueCollection
    {
        { "Content-Type", "application/json" },
        { "x-li-format", "json" }
    };
            client.Headers.Add(requestHeaders);
            var responseJson = client.UploadString(requestUrl, "POST", requestJson);
            var response = new JavaScriptSerializer().Deserialize<Dictionary<string, object>>(responseJson);
            return response.ContainsKey("updateKey");
        }
    }
I have use this but when i posting, i am getting 401 error(Authincation error)