Is there an expression to downcast and simultaneously access a property in F#?

Question

In C#, in order to access a property/method I might downcast to a type and then access the property:

Fruit f = new Banana();
((Banana)f).Peel();

What is the equivalent in F#? I tried the following but the intellisense after typing the period does not give any members of the Banana type so I'm guessing this isn't valid.

let f = new Banana()
(f :?> Banana).Peel() 

I know I can do it by introducing an intermediate let statement but was wondering if there was a one liner.

UPDATE

Ok I was trying to give a general example but I guess something got lost in my translation. I'm working with Excel interop. In any case here is the more specific code.

(worksheet.Cells.[rowNumber, dateColumn] :?> Excel.Range).<member here>

But it looks like it was just a temporary glitch in intellisense because today (after rebooting my computer) it seems to work fine. Yesterday it was just showing me basic object members of Equals, GetHashCode, GetType, and ToString. Now today this same expression is giving me all the members of the Excel.Range class. So I it looks like everything works as expected.

Answer 1

Your initial guess is correct, this code works:

type Fruit() =
    member me.Test() = printfn "Test"

type Banana() =
    inherit Fruit()
    member me.Peel() = printfn "Peeling !"

let f = new Banana() :> Fruit
(f :?> Banana).Peel()

You are not showing how did you define those types, probably you have something wrong there.

Also keep in mind that in F# you have to be explicit to upcast. In your example your f object is already a Banana, nothing in your code upcast it to a Fruit.