[HttpPost]
    public string ValidateAccount(string user, string password)
    {
        UserAccount account = new UserAccount();
        return account.Login(user, password);
    }

public class SendPostRequest extends AsyncTask<String, Void, String>
   {
    String username = edt_user.getText().toString();
    String password = edt_pass.getText().toString();

    @Override
    protected void onPreExecute() {
        pb_bar.setVisibility(View.VISIBLE);
    }

    @Override
    protected String doInBackground(String... params) {
        HttpURLConnection conn = null;
        try
        {
            java.net.URL url = new URL("http://192.190.191.97:65/api/AuthenticateUser/ValidateAccount");
            JSONObject postDataParams = new JSONObject();
            postDataParams.put("user", username);
            postDataParams.put("password", password);

            Log.e("params", postDataParams.toString());

            conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(15000); /* milliseconds */
            conn.setConnectTimeout(15000); /* milliseconds */
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);

            OutputStream os = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));
            writer.write(getPostDataString(postDataParams));

            writer.flush();
            writer.close();
            os.close();

            int responseCode = conn.getResponseCode();

            if (responseCode == HttpsURLConnection.HTTP_OK)
            {
                BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                StringBuffer sb = new StringBuffer("");

                String line = "";
                while ((line = in.readLine()) != null)
                {
                    sb.append(line);
                    break;
                }
                in.close();
                return sb.toString();
            }
            else
            {
                return new String("false : " + responseCode);
            }
        }
        catch (Exception e) {
            return new String("Exception: " + e.getMessage());
        }
        finally
        {
            conn.disconnect();
        }

    }

    @Override
    protected void onPostExecute(String r) {
        pb_bar.setVisibility(View.GONE);
        Toast.makeText(getApplicationContext(), r, Toast.LENGTH_LONG).show();

    }

    public String getPostDataString(JSONObject params) throws Exception
    {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        Iterator<String> itr = params.keys();
        while (itr.hasNext())
        {
            String key = itr.next();
            Object value = params.get(key);

            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(key, "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(value.toString(), "UTF-8"));

        }
        return result.toString();
    }
}