public WorkflowCommandExtensionItem(IWorkflowCommandExtensionCallback callback)
 {
     if (null == callback)
     {
         throw FxTrace.Exception.AsError(new ArgumentNullException("callback"));
     }
     this.CommandExtensionCallback = callback;
 }
 public WorkflowCommandExtensionItem(IWorkflowCommandExtensionCallback callback)
 {
     if (null == callback)
     {
         throw FxTrace.Exception.AsError(new ArgumentNullException("callback"));
     }
     this.CommandExtensionCallback = callback;
 }