.NET, Microsoft, Visual Basic, C#, CLR, VB.Net, parameter arrays, parameters
While most modern programming languages provide some way of declaring optional function parameters, C# doesn't provide a way of directly doing so, despite the fact that VB.Net and .Net's attribute system both support this functionality. This is a subject of some debate currently in the C# community. The C# development team's position seems to boil down to the following: When provided, this feature is usually nothing more than dressing up method overloading with a little syntactic sugar.
When you get right down to it, their position makes some sense. A function with an optional parameter is in reality two different functions: one that assumes some default behavior if the optional parameter is omitted, and another that performs more specific behavior based on the value of the optional parameter if provided. But that doesn't change the fact that using overloaded methods to provide optional parameter support feels a little clunky. It works, but you always wind up writing more code, and you pollute your object interface with the extra method signatures required to support all of your optional parameters. Let's look at some alternatives.
Parameter arrays
If you take a look at the classes found in the common language runtime (CLR), you'll find more than a few with methods that can accept a variable-length list of parameters. One example would be the System.Console.WriteLine method, which has an overloaded declaration that works to support replaceable parameters in the string written to the console. For example, this code:
Console.WriteLine("{0} jumped over {1}.", "The cow", "the moon");In order to post a comment you need to be registered and logged in
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Talkback
This is a nice article. (one of very few articles available in the internet) on how to get around optional parameters in C#. Some of the hyperlinks like listingA and listingB don't work.
26 Aug 03 21:29 ReplyIt will be very helpful if we could see your code sample. Thanks.
Nice article.
24 Mar 06 00:20 ReplyI found this while searching for a solution/way using optional parameter at C#.
It is very bad that C# doesn't have optional parameters. No solution is good as natural support :(