title: Random String Generator Returning Same String
body: <p>I've developed a random string generator but it's not behaving quite as I'm hoping.  My goal is to be able to run this twice and generate two distinct four character random strings.  However, it just generates one four character random string twice.</p>
  
  <p>Here's the code and an example of its output:</p>
  
  <pre><code>private string RandomString(int size)
  {
      StringBuilder builder = new StringBuilder();
      Random random = new Random();
      char ch;
      for (int i = 0; i &lt; size; i++)
      {
          ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));                 
          builder.Append(ch);
      }
  
      return builder.ToString();
  }
  
  // get 1st random string 
  string Rand1 = RandomString(4);
  
  // get 2nd random string 
  string Rand2 = RandomString(4);
  
  // create full rand string
  string docNum = Rand1 + "-" + Rand2;
  </code></pre>
  
  <p>...and the output looks like this:  UNTE-UNTE
  ...but it should look something like this UNTE-FWNU</p>
  
  <p>How can I ensure two distinctly random strings?</p>