Extension method: Difference between revisions

Revision as of 23:11, 2 January 2008

Revision as of 05:01, 3 January 2008

Line 43:

With extension methods: "x.Operation1(arg1).Operation2(arg2)"

==The versioning problem==

Instance methods are always preferred over extension methods, even when new instance methods replace previously-existing extension methods. However, Visual Studio gives no warning about naming conflicts. Consider this C# code:

<source lang="csharp">

class AlphabetMaker { }

static class ExtensionMethods

{

static public string GetAlphabet(this AlphabetMaker am)

{

return "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

}

}

</source>

The GetAlphabet extension method can be called in this way:

<source lang="csharp">

AlphabetMaker am = new AlphabetMaker();

Console.WriteLine(am.GetAlphabet()); // output: ABCDEFGHIJKLMNOPQRSTUVWXYZ

</source>

An instance method is then added to the AlphabetMaker class:

<source lang="csharp">

class AlphabetMaker

{

public string GetAlphabet()

{

return "abc";

}

}

</source>

The same code using AlphabetMaker now returns a different result:

<source lang="csharp">

AlphabetMaker am = new AlphabetMaker();

Console.WriteLine(am.GetAlphabet()); // output: abc

</source>

The new instance method has replaced the extension method, but the Visual Studio compiler gives no indication that a naming conflict exists.

==See also==