title: StackExchange.Redis string value is converted to set
body: <p>I use StackExchange.Redis to work with cache.
  I have action which returns values from cache (if value exists)</p>
  
  <pre><code>public ActionResult GetCalculatorSalaries()
      {
          var s = (string) _cache.StringGet("CalculatorSalaries");
          if (String.IsNullOrEmpty(s))
          {
              var salaries = _service.LoadCalculatorSalaries();
              _cache.SetAdd("CalculatorSalaries", (string)salaries);
              return Json(salaries, JsonRequestBehavior.AllowGet);
          }
          return Json(s, JsonRequestBehavior.AllowGet);
      }
  </code></pre>
  
  <p><code>_service.LoadCalculatorSalaries();</code> - this is service which returns data from Azure Blob and here returns data as <code>string</code>.</p>
  
  <p>Problem: I set value for key "CalculatorSalaries" as <code>string</code> but when i try to get it, i get an <code>error</code>, as value by that key is of type <code>set</code>. </p>
  
  <p>Where i am wrong?</p>
  
  <hr>
  
  <p>P.S. When i debug code at step </p>
  
  <p><code>var s = (string) _cache.StringGet("CalculatorSalaries");</code> </p>
  
  <p>debuging skiping when value exists for key "CalculatorSalaries" and error get only in browser console</p>