Sending a WFS-T request

I have a geoserver which I want to edit using c-sharp, I managed to retrieve information from it, but I haven’t found a way to make any changes – I know that there is WFS-T but I haven’t found a way to initialize it, I made the xml file (with my insert/delete/update), but I’m not sure how to send it to my geoserver, how can I send it using csharp?

URL = "http://localhost:8080/geoserver/topp"

XML file:

<?xml version="1.0" ?>
<wfs:Transaction
   version="2.0.0"
   service="WFS"
   xmlns:fes="http://www.opengis.net/fes/2.0"
   xmlns:wfs="http://www.opengis.net/wfs/2.0"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.opengis.net/wfs/2.0
                       http://schemas.opengis.net/wfs/2.0.0/wfs.xsd">
   <wfs:Update typeName="topp:states">
      <wfs:Property>
         <wfs:ValueReference>STATE_NAME</wfs:ValueReference>
         <wfs:Value>Caliwhilenia</wfs:Value>
      </wfs:Property>
      <ogc:Filter>
         <ogc:PropertyName>STATE_NAME</ogc:PropertyName>
         <ogc:Literal>California</ogc:Literal>
      </ogc:Filter>
   </wfs:Update>
</wfs:Transaction>

request code

 WebRequest request = WebRequest.Create(url); //the geoserver url

    request.ContentType = "text/xml";
    request.Method = "POST";
    request.Credentials = new NetworkCredential("admin", "geoserver");

    byte[] buffer = File.ReadAllBytes(xmlrequest); //Makes a change to the state's name
    Stream reqstr = request.GetRequestStream();
    reqstr.Write(buffer, 0, buffer.Length);
    reqstr.Close();

    WebResponse response = request.GetResponse();

The geoserver is not changing the state’s name

Update: now it connects to the server but I’m getting a “OperationParsingFailed” exception, altough I find that there is noting wrong with my xml file