Interacting with MySQL using PHP and C#

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C#

PHP

MySQL

I want to insert, update and read data using PHP and C#, is there a library to do this, if not does anyone have any information to help me along, with some experimenting I got this to work:

Example 1: I managed to get a sum working using PHP and C#

PHP Code:

<?php echo (int)$_GET["a"] + (int)$_GET["b"]; ?>

C# Code:

using (var client = new WebClient())
          {
              var a = 50;
              var b = 100;
              var result = client.DownloadString(string.Format("http://antivurusdownload.co.uk/test/csharptest.php?a={0}&b={1}", a, b));
              Console.WriteLine(result);
              Console.ReadKey();
          }

Now I tried to apply this to MySQL using this code to no success

PHP Code:

<?php

$username="testing123";
$password="helloworld";
$joindate="21/10/2013 - 21:00";
$active=1;

$con=mysqli_connect("localhost","root","password","database");
// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }

mysqli_query($con,"INSERT INTO user (username, password, joindate, active) VALUES ($username, $password, $joindate, $active)");

mysqli_close($con);
?>

Can anyone help!? Thanks!