title: Convert a 4 char string into int32
body: <p>Is there a fast way to convert 4 chars into a 32bit int?  I know i can loop through it like :</p>
  
  <pre><code>string key = "ABCD";
  int val = 0;
  for (int i = 0; i &lt; 4; i++)
  {
      int b = (int)key[i] * (int)Math.Pow(256, i);
      val += b;
  }
  // val = 1145258561
  </code></pre>
  
  <p>I would like something lower level, I know the chars are stored as bytes.  I don't mind if its unsafe code because I am basically trying to write a 4 char string to an integer pointer location.</p>