title: Convert stringbuilder objects to double
body: <p>I'm trying to create a calculator, which is capable of doing line calculations like the windows calculator.</p>
  
  <p>To call my calculation function I try to use a stringbuilder. Everytime for instance 5 is pressed I use </p>
  
  <p>Class declarations:</p>
  
  <pre><code> StringBuilder ccSb = new StringBuilder();
   double ccSub = 0;
   String ccOutput = "";
  </code></pre>
  
  <hr>
  
  <pre><code>ccSb.Append("5");
  ccSub = Convert.ToDouble(ccSb);
  ccOutput = Rechner.rechnen(ccSub, ccCurrentOp, ccOperatorPressed);
  </code></pre>
  
  <p>However the Convert.ToDouble throws the exception that the</p>
  
  <blockquote>
    <p>Stringbuilder object is not convertable to System.IConvertible.</p>
  </blockquote>
  
  <p>Is there any workaround or any other way to get the pressed numbers and save them into a double?</p>