Get value of optional types when retrieving value of record fields in F# - reflection

Question

I have a type defined as follows:
type Employee = {
Id: Guid
Name: string
Phone: string
Email: Option<string>
}
and an instance of this type:
let emp = {
Id = Guid "bc07e94c-b376-45a2-928b-508b888802c9"
Name = "A"
Phone = "B"
Email = Some "E"
}
I want to extract the field names and values from this record type using reflection like the following:
let getFieldValueMappingOfARecordType (data: 'T) : seq<string * obj> =
let fieldValueMapping =
data.GetType()
|> FSharpType.GetRecordFields
|> Seq.map (
fun propertyInfo ->
(propertyInfo.Name, data |> propertyInfo.GetValue)
)
fieldValueMapping
Then invoking the above function with the instance of employee type
let mapping = getFieldValueMappingOfARecordType emp
|> Seq.toList
gives us:
val mapping : (string * obj) list =
[("Id", bc07e94c-b376-45a2-928b-508b888802c9); ("Name", "A"); ("Phone", "B");
("Email", Some "E")]
So far it's working well with non-optional type. But in case of optional types, it's returning the value of the field as either Some value or None. What I would like to do is to get the value when the field has Some value or make it null when it's None.
Essentially like the follwing:
val mapping : (string * obj) list =
[("Id", bc07e94c-b376-45a2-928b-508b888802c9); ("Name", "A"); ("Phone", "B");
("Email", "E")]
Or if the employee instance is like the following:
let emp = {
Id = Guid "bc07e94c-b376-45a2-928b-508b888802c9"
Name = "A"
Phone = "B"
Email = None
}
Then,
val mapping : (string * obj) list =
[("Id", bc07e94c-b376-45a2-928b-508b888802c9); ("Name", "A"); ("Phone", "B");
("Email", null)]
This is what I have so far (non-working code):
open System
open Microsoft.FSharp.Reflection
open System.Reflection
type Employee = {
Id: Guid
Name: string
Phone: string
Email: Option<string>
}
let emp = {
Id = Guid "bc07e94c-b376-45a2-928b-508b888802c9"
Name = "A"
Phone = "B"
Email = Some "E"
}
let getSomeOrNull (t: Type) (o: obj) =
let opt = typedefof<option<_>>.MakeGenericType [| t |]
match (o :?> opt) with
| Some s ->
s
| None ->
null
let getValues (data: 'T) =
let values =
data.GetType()
|> FSharpType.GetRecordFields
|> Array.map (
fun propertyInfo ->
let value =
data |> propertyInfo.GetValue
let isOption =
propertyInfo.PropertyType.IsGenericType && propertyInfo.PropertyType.GetGenericTypeDefinition() = typedefof<Option<_>>
match isOption with
| true ->
(propertyInfo.Name, (getSomeOrNull propertyInfo.PropertyType value))
| false ->
(propertyInfo.Name, value)
)
values
getValues emp
|> printfn "%A"

Answer 1

I think the only way to do this is with reflection:
let getSomeOrNull (t: Type) (o: obj) =
if isNull o then null
else t.GetProperty("Value").GetValue(o)

Answer 2

I think this should do the trick:
let getSomeOrNull (o: obj) =
match o with
| :? Option<string> as o -> a |> Option.toObj > box
| _ -> null