How to pass a byref value to Delegate.DynamicInvoke?

Question

I'm trying the following code:

let orig = ref <| Vector(X = 1, Y = 1)
native.DynamicInvoke[| box orig |] |> ignore

But it results in ArgumentException (FSharpRef[Vector] cannot be converted to Vector&)

Answer 1

You should have a look this: Parameters and Arguments

TL;TR: you can use the "&" Operator (similar to C++) to pass something as a byref

Just make sure it's mutable - so this should work:

let mutable orig = Vector(X = 1, Y = 1)
native.DynamicInvoke[| &(box orig) |] |> ignore

What I don't get is why you need a byref at all - AFAIK the DynamicInvoke needs just a param-array - can you give a working snippet so I can try?

Answer 2

I don't think your code works.

Also, nevermind, I found solution.

let args = [| box valueTypeValue |]
native.DynamicInvoke args |> ignore
assert(not <| valueTypeValue.Equals(args.[0]))

So if native is of C# type

delegate void NativeDelegate(ref SomeValueType v)

and is changing v, then after calling DynamicInvoke corresponding arg in arguments array (this time - args) will be overwritten.