F# function parameters

From the google search, it is easy to find how to handle C#'s out/ref parameter in F#. This post tries to summarize the out/ref parameter between F# and C#. Both from C# to F# and F# to C#.

• F# invoke C#

the C# code defines the following method inside ConsoleApplication1.Program class.

        public void OutTo9(out int i)

        {

            i = 9;

        }

        public int OutTo8(out int i)

        {

            i = 8;

            return 1;

        }

        public void RefTo10(ref int i)

        {

            i = 10;

        }

the F# needs to invoke the above function like:

        let a = ConsoleApplication1.Program()

        let b = a.OutTo9()

        let (returnValue, outValue) = a.OutTo8()

        let c = ref 0;

        a.RefTo10(c)

• C# invoke F#

We define the F# code like:

//please remove extra space around < and > if the code does not compile. The blog does not support the character.

type MyClass() = class

    member public this.OutTo8([< System.Runtime.InteropServices.Out >]outValue:byref) = 

        outValue < - 8

    member public this.RefTo4(args:byref< int >) = 

        args < - 4

end

In the C# code, you can see:

            var a = new MyClass();

            int b = 0;

            a.OutTo8(out b);

            Console.WriteLine(b);

            a.RefTo4(ref b);

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