Sunday, May 1, 2011

Using extension methods defined in C# from F# code

I have a series of extension methods defined for various classes in a C# library. I'm currently writing some F# code and instead of rewriting that code I would simply like to use my existing extension methods in my F# code.

I have added a reference to the library and used the open statement to import the namespace, but the extension methods to not appear in F#

From stackoverflow
  • Update:

    In the current version of F#, you can simply consume extension methods by adding

    open TheNamespaceOfExtensionMethod
    

    to your source file (just like you do in C# with a using directive) and simply call the extension method as if it was a normal instance method.

    By the way, you can always call them directly just like a normal static method and pass the object reference as the first parameter without any directives if you want. An extension method is simply a static method decorated with ExtensionAttribute under the hood.

    Original answer (before F# 2010 beta; not true anymore, as Dykam points out):

    I don't think extension methods are supported by F#. You can always call them directly just like a normal static method and pass the object reference as the first parameter.

    TimothyP : Thnx for the info... lol and why didn't I think of that :p
    Steve Haigh : +1. Exactly, extension methods are a language feature, not a CLR feature. They are really syntactic sugar to make certain kinds of static method look like instance methods.
    Dykam : Not true anymore.
  • Being able to 'import' C#/VB extension methods will be supported in the next release of F#.

    See also

    http://stackoverflow.com/questions/702256/f-extensions-in-c

    for more detail on the topic.

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