Question

I have some code that looks like this:

public Tuple<bool, SomeObjectModel> CheckIfJsonIsValid(string IncomingJson)
{
   SomeObjectModel TheObjectModel = new SomeObjectModel();
   JavascriptSerializer TheSerializer = new JavascriptSerializer();
   .....

   try
   {
       TheObjectModel = TheSerializer.Deserialize<SomeObjectModel>(IncomingJson);
   }
   catch
   {
       return new Tuple<bool, SomeObjectModel>(false, null); //question here
   }

   .....
   return new Tuple<bool, SomeObjectModel>(true, TheObjectModel);
}

The calling method first check the returning tuple’s Item1, and if it’s false, ends its process.

Is it better practice a) to return a null value in the Tuple or b) to return a new and fresh instance of SomeObjectModel? Are there any performance implications?

Thanks for your suggestions.

Answer 1

Let me suggest three alternative solutions:

---

ParseJsonIfValid: If deserializing works, TheObjectModel is always non-null. Thus, there is no need for the boolean:

public SomeObjectModel ParseJsonIfValid(string IncomingJson)
{
   JavascriptSerializer TheSerializer = new JavascriptSerializer();
   .....

   try
   {
       return TheSerializer.Deserialize<SomeObjectModel>(IncomingJson);
   }
   catch
   {
       return null;
   }
}

In the calling function simply check whether the return value is null or not.

---

ParseJson: If the JSON is usually valid, and invalid JSON is a sign of something gone terribly wrong, just throw an exception:

public SomeObjectModel ParseJson(string IncomingJson)
{
   JavascriptSerializer TheSerializer = new JavascriptSerializer();
   .....

   try
   {
       return TheSerializer.Deserialize<SomeObjectModel>(IncomingJson);
   }
   catch (Exception e)
   {
       throw new TheServerSentRubbishException(e);
   }
}

Be sure to include the inner (“real”) exception, so that the calling function can log the real cause of the error for debugging purposes.

---

TryParseJson: If null can be a valid deserialization, you can use the following pattern, which has the advantage of being consistent with the TryParse methods of the .NET framework:

public bool TryParseJson(string IncomingJson, out SomeObjectModel theObjectModel)
{
   JavascriptSerializer TheSerializer = new JavascriptSerializer();
   .....

   try
   {
       theObjectModel = TheSerializer.Deserialize<SomeObjectModel>(IncomingJson);
       return true;
   }
   catch (Exception e)
   {
       return false;
   }
}