C# – How to use C# object from F#

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I have the following C# code.

namespace MyMath {
    public class Arith {
        public Arith() {}
        public int Add(int x, int y) {
            return x + y;
        }
    }
}

And I came up with the F# code named testcs.fs to use this object.

open MyMath.Arith
let x = Add(10,20)

When I run the following command

fsc -r:MyMath.dll testcs.fs

I got this error message.

/Users/smcho/Desktop/cs/namespace/testcs.fs(1,13): error FS0039: The namespace 'Arith' is 
not defined

/Users/smcho/Desktop/cs/namespace/testcs.fs(3,9): error FS0039: The value or constructor 
'Add' is not defined

What might be wrong? I used mono for .NET environment.

Best Answer

try

open MyMath
let arith = Arith() // create instance of Arith
let x = arith.Add(10, 20) // call method Add

Arith in your code is class name, you cannot open it like namespace. Possibly you are confused with ability to open F# modules so its functions can be used without qualification

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C# – How to cast int to enum

From an int:

YourEnum foo = (YourEnum)yourInt;

From a string:

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

// The foo.ToString().Contains(",") check is necessary for enumerations marked with an [Flags] attribute
if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(","))
{
    throw new InvalidOperationException($"{yourString} is not an underlying value of the YourEnum enumeration.")
}

Update:

From number you can also

YourEnum foo = (YourEnum)Enum.ToObject(typeof(YourEnum) , yourInt);

C# – How to enumerate an enum

foreach (Suit suit in (Suit[]) Enum.GetValues(typeof(Suit)))
{
}

Note: The cast to (Suit[]) is not strictly necessary, but it does make the code 0.5 ns faster.

Best Answer

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C# – How to cast int to enum

C# – How to enumerate an enum

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