CODEWITHSUNDEEP
reflectionf#
Robur_131
Robur_131

Reputation: 694

System.InvalidCastException: Specified cast is not valid when trying to use Reflection in F#

I am trying to construct a record type in F#. But the following code is giving System.InvalidCastException. I am new to F# and having a difficult time understanding as to why this isn't working. A detailed explanation would be much appreciated.

open System
open Microsoft.FSharp.Reflection

type Employee = {
    Id:          Guid
    Name:        string
    Phone:       string
    BadgeId:     string
    Designation: string
}

let values =
    [
        "bc07e94c-b376-45a2-928b-508b888802c9"
        "A"
        "B"
        "C"
        "D"
    ]
    |> Seq.ofList

let creator = FSharpValue.PreComputeRecordConstructor(typeof<Employee>, System.Reflection.BindingFlags.Public)

let x =
    (
        creator [|
            values
            |> Seq.map (fun y -> y)
        |]

    ) :?> Employee

printfn "%A" x

Upvotes: 1

Views: 204

Answers (1)

Tomas Petricek
Tomas Petricek

Reputation: 243041

There are two issues with your code. First, your record expects a value of type Guid, but you are giving it a guid as a string. You can fix this by boxing everyting in your values list:

let values =
    [
        box (Guid("bc07e94c-b376-45a2-928b-508b888802c9"))
        box "A"
        box "B"
        box "C"
        box "D"
    ]

The second issue is that you call creator with an array containing a sequence as an argument (there is an extra wrapping). You need to give it array containing the values:

let emp = creator (Array.ofSeq values) :?> Employee

Upvotes: 3

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