Re: [Saxdotnet-devel] String.Empty vs. null

[Karl W. <ka...@wa...>]

Jeff Rafter wrote:
>> One could think of this as a guideline:
>>
>> - If we would say: this string parameter/argument/value
>>   can be absent, then let's use null to indicate it.
>> - If we would rather say: this string parameter/argument/value
>>   can be empty, then let's use "" to indicate it.
>>
>> Coming back to the SAX API:
>> How would the above guideline be resolved for namespace URIs
>> and prefixes when an XML name is not in any namespace?
> 
> 
> I think that these are good guidelines-- and tough to argue with... but 
> for namespace URIs I think there is some ambiguity still...
> 
> a) <foo/>
> b) <foo xmlns="http://foo"/>
> c) <foo xmlns=""/>
> 
> Most naturally I would see this as
> 
> a) null
> b) "http://foo"
> c) string.empty

Are you asking what to pass for the namespace uri of foo
in the StartElementHandler()?

a) don't know, depends if there is a default namespace
b) "http://foo"
c) null (there is no namespace for foo)

We really only have two cases: foo has a namespace, or it doesn't.

Or did you mean something else?

> But I could see this making for needlessly complex handler code. Which 
> is why we want to land on either null or string.empty. string.empty 
> gives you less chance of a runtime exception but does not represent case 
> (a) very well. Using null does not represent (c) very well. I think that 
> in the XML Corpus this is one of the few areas where "" has a specific 
> meaning. You brought up arguments about API consistency and should we 
> use string.empty if no Public ID is provided (for instance)... but what 
> about the case where you have:
> 
> <foo bar="">
> 
> Would the bar attribute's value be null or string.empty?

String.Empty. null would mean: no value.

Karl