Questions to convert a code

Hi, I'm trying to convert a plugin and I don't know what is best way using MVC and Razor.
The code above uses Dataset.ReadXml to read a specified TexReader and XmlReadMode.

What is the best way to replace the use of DATASET in MVC?
      
      //Function that invoke method Enviar
            string msg = this.XMLHeader() + "\n" +
                   "<requisicao-transacao id=\"" + DateTime.Now.ToString("yyyyMMdd") + DateTime.Now.ToString("hhmmss") + "\" versao=\"" + VERSAO + "\">" + "\n   "
                        + this.XMLDadosEc() + "\n   ";
            if (incluirPortador == true)
            {
                msg += this.XMLDadosPortador() + "\n   ";
            }
            msg += this.XMLDadosPedido() + "\n   " //<-- each function returns string
                        + this.XMLFormaPagamento() + "\n   "
                        + this.XMLUrlRetorno() + "\n   "
                        + this.XMLAutorizar() + "\n   "
                        + this.XMLCapturar() + "\n";
            msg += "</requisicao-transacao>";
            System.Data.DataSet objResposta = this.Enviar(msg);
            return objResposta;

    public System.Data.DataSet Enviar(string vmPost)
        {
            byte[] byteBuffer = Encoding.UTF8.GetBytes("mensagem=" + vmPost);
            Stream requestStream = null;
            WebResponse response = null;
            StreamReader reader = null;
            
            WebRequest request;
            if (this._paymentCieloSettigns.usarUrlTeste) request = WebRequest.Create(this._paymentCieloSettigns.urlTeste);
            else request = WebRequest.Create(this._paymentCieloSettigns.urlProducao);

            request.Method = WebRequestMethods.Http.Post;
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = byteBuffer.Length;

            requestStream = request.GetRequestStream();
            requestStream.Write(byteBuffer, 0, byteBuffer.Length);
            requestStream.Close();

            response = request.GetResponse();
            Stream responseStream = response.GetResponseStream();
            System.Text.Encoding encoding = System.Text.Encoding.Default;
            reader = new StreamReader(responseStream, encoding);
            Char[] charBuffer = new Char[256];
            int count = reader.Read(charBuffer, 0, charBuffer.Length);

            StringBuilder Dados = new StringBuilder();
            while (count > 0)
            {
                Dados.Append(new String(charBuffer, 0, count));
                count = reader.Read(charBuffer, 0, charBuffer.Length);
            }

            System.Data.DataSet ds = new System.Data.DataSet();
            
            ds.ReadXml(new StringReader(Dados.ToString()), System.Data.XmlReadMode.Auto);
            return ds;
        }
  
Thanks