On page 99 (I think) there is a discussion that the default for parameters is ByVal in VB.Net vs. ByRef in VB6. Then the text goes on to state that this is much better because ByRef is higher overhead because the data must be copied to the sub or function and then copied back once the sub or function completes.

I hope that this is an incorrect description of the way ByRef parameters are passed. I believe that the address of the ByRef variable(s) are copied at the call to the subprogram. Then the subprogram uses/modifies the variable that is in one, and only location, in memory. At the exit from the subprogram there is no copying back of the ByRef parameters.

If my understanding of subprogram calls is correct, then the book is wrong. ByVal parameters have higher overhead but are much safer because they remove the possibility of unintended consequences of data modification for the calling program.

Any feedback would be appreciated.

Greg
[email protected]

Greg,
The answer to your question is that it depends on which version of .NET you are using. The book was written to version 1.0 and in version 1.0 ByRef parameters were not handled as you expect which is why that specific item was called out, as it relates to the material that was available and which the book covered, the book is correct. (It is also why Microsoft changed the default for parameters which hopefully someday they will change back)

However, If like most developers you have migrated to version 1.1 of .NET then you will find that .NET has been updated and works much closer to what you expect. When/if an edition that reflects .NET version 1.1 is released this would be one of the items to be updated.
Bill

  Any updates / confirmation on this? 1.1 has been out awhile and I can't find any confirmation on google...

Thanks for posting the link BillS.

XUMUSKIEFAN
Wrox Moderator