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Program.fs

open System
open Microsoft.FSharp.Quotations
open FSharp.Quotations.Evaluator

type A (str: string) =
    member val Prop: string = str with get, set

let inline safeGet (f: Expr<'T>): 'T option =
    try Some(f.Evaluate())
    with :? NullReferenceException -> None

[<EntryPoint>]
let main argv =
    let a = A(null)
    printfn "%A" (safeGet <@ a.Prop.Length @>)

    let b = A("123")
    printfn "%A" (safeGet <@ b.Prop.Length @>)

    0