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Using an array as an optional parameter

  Asked By: Rani    Date: Nov 27    Category: Asp.net    Views: 2105
  

I'm trying to use an optional array in a Sub but am having trouble
figuring out how to assign the default value.

For instance:
Sub MySub(Optional MyString as String() = ... )

I want to put an empty array in there but can't quite figure out how
that should work.

Can someone point me in the right direction?

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3 Answers Found

 
Answer #1    Answered By: Haboos Kauser     Answered On: Nov 27

Optional arguments are probably the wrong way and not CLS compliant.

Overloading is better.


Sub MySub( )
Dim strParm() As String = {"up", "down", "left", "right"}
Call MySub(strParm())
End Sub


Sub MySub(MyString as String() )
.....
End Sub

 
Answer #2    Answered By: Hadil Khan     Answered On: Nov 27

Are there any performance hits to using optional  params? What do you mean
by CLS compliant? I always kind of thought it all compiled down to the same
code when it was all said and done.

 
Answer #3    Answered By: Dale Jones     Answered On: Nov 27

Basically there are some things you can do in C# and VB.net that means
other languages may not be able to inherit the code and/or consume it properly.

For example C# supports unsigned INTs which are not a type that all .net
languages are guaranteed to support. If one used them as parameters to a
function a language like VB.net or Perl.net could not call that function.

If the unsigned INT happened inside the function any language could call
that function but if it appeared as parameter/signature a language that
could not construct an unsigned INT would have trouble calling it.

Same thing with Case Sensitive methods in C#

C# could call a DoTask() or doTask() method and would be calling 2 distinct
methods because their are 2 separate mothods case-sensitivity is what makes
them different.

If VB.net called the function Dotask or any of the capitalization variants
it would be ambigous which to call so we would call the C# class with case
sensitive methods "NOT CLS compliant".

C# and VB.net compilers have switches to check for CLS compliant and warn
if violated.


There are other good practices besides CLS compliance that FXCOP can catch.....
http://www.gotdotnet.com/team/libraries/
Just because code works and is fast enough does not ensure it is
written the best way.

 
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