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Should I return null or throw an exception?

Asked 2010-10-19T15:29:28.013
9

I found questions here Should a retrieval method return 'null' or throw an exception when it can't produce the return value? and Should functions return null or an empty object?, but I think my case is quite different.

I'm writing an application that consists of a webservice and a client. The webservice is responsible to access data, and return data to the client. I design my app like this:

//webservice

try
{
   DataTable data = GetSomeData(parameter);
   return data
}
catch (OopsException ex)
{
   //write some log here
   return null; 
}

//client:

   DataTable data = CallGetSomeData(parameter);
   if(data == null) 
   {
      MessageBox.Show("Oops Exception!");
      return;
   }

Well, there is a rule of not returning null. I don't think that I should just rethrow an exception and let the client catch SoapException. What's your comment? Is there better approach to solve this problem?

Thank you.

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2 Answers

0

The general practice in handling exception is, when the sequence of flow is expected in the normal circumstance where as the sequence could not be completed due to non-availability of resources or expected input.

In your case, you still need to decide how do you want your client side code to react for null or exception.

answered 2010-10-19T15:40:17.050
0
  • Since you are the client to your webservice, you can log the exception at the service layer and return null to the client, yet the client should still know if the CallGetSomeData returned null because a) data is not available, or b) there is a database exception as the table is locked. Hence its always good to know what has caused the error for easier reporting at client side. You should have a error code and description as part of your message.
  • If you are not consuming your webservice then you should definetly throw exception for the same reasons mentioned above, client should know what has happened and its upto them to decide to what to do with that.
answered 2010-10-29T20:37:13.773

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