C# Optional Parameters?

[Covean]

If the fourth parameter has this relevance why do you set some default value? Wouldn't it be better to set it as 3rd parameter with no default value and let to compiler spit out like hell? By the way you would run in the same problem if there where no default value: Your example above without default values:

void func(string szParam1, string szParam2) { ... }
void func(string szParam1, string szParam2, string szParam3) { ... }

Now if you add some parameter with a default value it should look like this:

void func(string szParam1, string szParam2) { ... }
void func(string szParam1, string szParam2, string szParam3) { ... }
void func(string szParam1, string szParam2, string szParam3, string szParam4) { ... }

This is exactly the same problem. If you solve your problem by adding an important parameter with default value and asking yourself if you got all places where you need this parameter, then you have no problem with your source code. The problem lies in your application design. I really like it to get default values back. :-D And I never ran in the evil-default-value-problem in my whole lifetime!

Greetings Covean

[peterchen]

That's a point, but still... You can force the compiler find the location by just making them non-default. (Yo do have a batch build over all projects involved, don't you?)

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[RCoate]

Electron Shepherd wrote:

The function may be used by others, in ways that you don't know (and therefore won't test).

That argument doesn't make any sense to me. I don't see much difference between adding an optional parameter and providing a new overloaded method. The information that the new functionality is available still needs to be shared and then used appropriately. It seems to be mostly a matter of style and preference. Still, my main point in brining this topic up was that I was surprised that optional and named parameters were introduced in C# 4.0. It is something I did not expect to see.

[rastaVnuce]

That's really not the point. If the parameter is critical you don't set a default value. If it's not, it means that it makes difference for a finite number of cases which you're aware about. So, you set a default value which would be properly handled for the rest of the cases. I really don't see a place for confusion. Over a decade of experience in working with a ton of different languages and technologies, I've never had a single issue with the default parameter. On the contrary, I've missed it a lot where not available.

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[realJSOP]

Two words - side effects... What I've noticed is that only ex-VB programmers seem to be excited about optional and named parameters.

.45 ACP - because shooting twice is just silly
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[RCoate]

John Simmons / outlaw programmer wrote:

only ex-VB programmers seem to be excited about optional and named parameters

Not really excited, more surprised. But, yes guilty as charged. ;)

[WiGgLr]

I'm not convinced about optional parameters, but I can see a potential use for named parameters. That said, it's just more code to write, so I doubt I'd use them :)

[megaadam]

peterchen wrote:

public static void DisplayName (string firstName, string lastName = null) ==> public static void DisplayName (string firstName, string middleName = null, string lastName = null)

That does not compile, due to ambiguity: DisplayName( "Peter", "Not Chen" ); // Cannot be resolved to one of the two overloads

..................... Life is too shor

[peterchen]

I meant changing the prototype from one to another, the second argument suddenly becoming the middle name

megaadam wrote:

DisplayName( "Peter", "Not Chen" );

Who's that?

Agh! Reality! My Archnemesis![^]
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[Stuart Dootson]

RCoate wrote:

I do like the named parameters though. I have been wanting those ever since I did some Office Automation stuff.

I've loved named parameters since I first did some Ada programming in the mid 1990s...thy'r the one thing that makes optional parameters non-evil, IMO...

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[Dan Neely]

Electron Shepherd wrote:

How do you guarantee that you have passed in the fourth parameter everywhere you should have?

How do you know you called the 4 parameter overload everywhere you should have instead of the three parameter overload?

3x12=36 2x12=24 1x12=12 0x12=18

[Electron Shepherd]

Becuase my point was to make the parameters non-optional. Then the compiler spots all those cases for you.

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[PIEBALDconsult]

Electron Shepherd wrote:

I must need it in at least one place

Not if it's framework code that you may not be using at all. I write a lot of methods I never use.

[S Senthil Kumar]

You would have run into the same problem if you'd used method overloading instead of optional parameters; you'd still have to manually identify the places where the extra parameter should be used. Anyway, you could just comment out the = null and recompile again :)

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[PIEBALDconsult]

I finally tried one the other day, then refactored the need away. It's a good tool to have in the toolbox, but I don't expect to use it all that much.

[S Senthil Kumar]

John Simmons / outlaw programmer wrote:

side effects

Did you mean dependencies between parameters?

void Method(int x, int y) {}

int z = 2;
Method(y : z, x : ++z)

Regards Senthil _____________________________ My Home Page |My Blog | My Articles | My Flickr | WinMacro