Getting (400) Bad Request. when trying to send GCM Message
<p>I am trying to send message to GCM Server through C#.net</p>

<p>I found a good example that I am trying to use</p>

<p><a href="http://www.codewithasp.net/2015/11/send-message-gcm-c-sharp-single-multiple.html" rel="nofollow noreferrer">http://www.codewithasp.net/2015/11/send-message-gcm-c-sharp-single-multiple.html</a></p>

<p>The problem is that I get "The remote server returned an error: (400) Bad Request." error whenever I try to Get the response from this line </p>

<pre><code>            WebResponse wResponse = wRequest.GetResponse();
</code></pre>

<p>I tried to find what the prblem is, I changed the API code from Server to Android, to Browser, and the result is either (400) Bad request or (401) Unauthorized.</p>

<p>Not sure what I am doing wrong here, it looked very simple and straight forward in the example.</p>

<p>Help is much appreciated</p>

<p>Here is The code</p>

<pre><code>        NotificationManager nm = new NotificationManager();
        List&lt;string&gt; ls = new List&lt;string&gt;(new string[] { "ABCDEFGHIJKLMNOPQRSTUVWXYZ" });

        nm.SendNotification(ls, " Hi.. This is a test","Hi.. Title",1);
</code></pre>

<p>and here is the class</p>

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Script.Serialization;
using System.Net;
using System.Text;
using System.IO;

namespace WebApplication1
{

    public class NotificationManager
    {
        private class NotificationMessage
        {
            public string Title;
            public string Message;
            public long ItemId;
        }

        public NotificationManager()
        {
            //
            // TODO: Add constructor logic here
            //
        }

        public string SendNotification(List&lt;string&gt; deviceRegIds, string message, string title, long id)
        {
            try
            {
                string regIds = string.Join("\",\"", deviceRegIds);

                string AppId = "AIzaSyXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
                var SenderId = "1234567890";

                NotificationMessage nm = new NotificationMessage();
                nm.Title = title;
                nm.Message = message;
                nm.ItemId = id;

                var value = new JavaScriptSerializer().Serialize(nm);
                WebRequest wRequest;
                wRequest = WebRequest.Create("https://android.googleapis.com/gcm/send");
                wRequest.Method = "post";
                wRequest.ContentType = " application/json;charset=UTF-8";
                wRequest.Headers.Add(string.Format("Authorization: key={0}", AppId));

                wRequest.Headers.Add(string.Format("Sender: id={0}", SenderId));

                string postData = "{\"collapse_key\":\"score_update\",\"time_to_live\":108,\"delay_while_idle\":true,\"data\": { \"message\" : " + "\"" + value + "\",\"time\": " + "\"" + System.DateTime.Now.ToString() + "\"},\"registration_ids\":[\"" + regIds + "\"]}";

                Byte[] bytes = Encoding.UTF8.GetBytes(postData);
                wRequest.ContentLength = bytes.Length;

                Stream stream = wRequest.GetRequestStream();
                stream.Write(bytes, 0, bytes.Length);
                stream.Close();

                WebResponse wResponse = wRequest.GetResponse();

                stream = wResponse.GetResponseStream();

                StreamReader reader = new StreamReader(stream);

                String response = reader.ReadToEnd();

                HttpWebResponse httpResponse = (HttpWebResponse)wResponse;
                string status = httpResponse.StatusCode.ToString();

                reader.Close();
                stream.Close();
                wResponse.Close();

                if (status == "")
                {
                    return response;
                }
                else
                {
                    return "";
                }
            }
            catch( Exception ex)
            {
                return ex.ToString();
            }
        }
    }
}
</code></pre>

<p>Here is how I get the API ID and Sender ID</p>

<p><a href="https://i.stack.imgur.com/gzlet.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gzlet.png" alt="Sender ID"></a></p>

<p><a href="https://i.stack.imgur.com/ks7Bw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ks7Bw.png" alt="API ID"></a></p>