Can't Do StockQuanitity PATCH Using OData

I wrote a piece of code to GET the product ID by the SKU and then to update StockQuantity with using PATCH request.

 

The GET request is working as perfectly, but the PATCH request is returning an unauthorized error.

 

I've followed all instruction in the documentation but still, I'm not sure why I'm getting this error message.

 

 

public void UpdateQTY(string ProductId, int CurrentStock)
    {
        string publicKey = "xyz";
        string secretKey = "xyz";
        string method = "patch";
        string accept = "application/json, text/javascript, */*";
        string timestamp = DateTime.UtcNow.ToString("o");
        // FOR PATCH REQUEST
        string content = JsonConvert.SerializeObject(new { StockQuantity = 5 }); // assume stock is new stock is 5
        byte[] data = Encoding.UTF8.GetBytes(content);
        string contentMd5Hash = CreateContentMd5Hash(data);
        

        string url = "http://xyz:1260/odata/v1/Products("+ProductId+")";

        var uri = new Uri(url);
        if (uri.Query != null && uri.Query.Length > 0)
        {
            url = string.Concat(uri.GetLeftPart(UriPartial.Path), HttpUtility.UrlDecode(uri.Query));
        }

        var messageRepresentation = string.Join("\n",
                method.ToLower(),
                "",
                accept.ToLower(),
                url.ToLower(),
                timestamp,
                publicKey.ToLower()
                );

        string signature = CreateSignature(secretKey, messageRepresentation);

        var request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = method;
        request.Accept = accept;
        request.Headers.Add("Accept-Charset", "UTF-8");
        request.Headers.Add("SmartStore-Net-Api-PublicKey", publicKey);
        request.Headers.Add("SmartStore-Net-Api-Date", timestamp);
        request.Headers.Add("Authorization", "SmNetHmac1" + signature);
        request.ContentLength = data.Length;
        request.ContentType = "application/json; charset=utf-8";
        request.Headers.Add("Content-MD5", contentMd5Hash);

        var stream = request.GetRequestStream();
        
        stream.Write(data, 0, data.Length);
        stream.Close();

        WebResponse response = request.GetResponse();

        Console.WriteLine(((HttpWebResponse)response).StatusDescription);

        // Get the stream containing content returned by the server.  
        // The using block ensures the stream is automatically closed.
        using (stream = response.GetResponseStream())
        {
            // Open the stream using a StreamReader for easy access.  
            StreamReader reader = new StreamReader(stream);
            // Read the content.  
            string responseFromServer = reader.ReadToEnd();
            // Display the content.  
            Console.WriteLine(responseFromServer);
        }

        // Close the response.  
        response.Close();





    }

It would be helpful to provide the exact error message including the response header, especially HmacResultId and HmacResultDesc that gives a hint to details about the error. contentMd5Hash is missing in your message representation. And it looks like there's a missing space character in your authorization header code, example

Authorization: SmNetHmac1 8puWspyJ3j7mb3SLdsFRo7+5EOsEX783nBfBOyKuml4=