What is a more efficient way to do a nested if statement in C#?

I have a code similar to the one shown below, and I am wondering if there is a more efficient way to code this method in mvc.

  public ActionResult LogViewerFiles([DataSourceRequest] DataSourceRequest request, string testValue, string testValue2)

    {
        if (string.IsNullOrWhiteSpace(testValue2) && string.IsNullOrWhiteSpace(testValue))
        {
            return View();
        }
        if (!string.IsNullOrWhiteSpace(testValue))
        {
           var fileName = testValue;
           var logEntries = LogEntry.ReadLogEntries(fileName);

            if (logEntries == null)
            {
                return JavaScript("Callback()");                  
            }
            return Json(logEntries.ToDataSourceResult(request), JsonRequestBehavior.AllowGet);
        }
        if (testValue2!= null)
        {
            var resultPath = testValue2;
            var logEntriesArch = LogEntry.ReadLogEntries(resultPath);
            return Json(logEntriesArch.ToDataSourceResult(request), JsonRequestBehavior.AllowGet);
        }
        return null;
    }

Basically what I am attempting to achieve is to execute different if statements, depending on the value of my arguments. In this case, only one argument will have the information I need to execute the code, and the other argument will always be null. This method is written so all the information gathered can be displayed in a kendo razor grid.