DapperLib
TypeHandler Override -> SetValue not being called.
I have posted this on StackOverflow but I think it might be a bug, unless I'm missing something super simple.
Am trying to add a custom type handler for an F# Union Type. ParseValue works fine but SetValue does not seem to get called at all.
type PrimaryKey<'x> =
| Id of int
| EmptyPrimaryKey
..
type PrimaryKeyHandler<'X>() =
inherit SqlMapper.TypeHandler<PrimaryKey<'X>>()
override _.SetValue(param, value) =
let valueOrNull =
match value with
| Id x -> box x
| EmptyPrimaryKey -> null
param.DbType <- DbType.Int32 (* Put in as a test , doesn't seem to do anything*)
param.Value <- valueOrNull
override _.Parse value =
if isNull value || value = box DBNull.Value
then EmptyPrimaryKey
else Id (value :?> int)
Anything obvious jump out here?
Does it not get called when there is a value present or when it is null (ie the result in the answer from the db is null)? I have a solution open for a null handler (they are ignored totally at the moment).
Very likely the value was null. I can’t remember if I tested with a value or not, seems like something I’d do.
From what I recall, putting a breakpoint in the function indicated that it was simply not being called at all.
I will double check and get back to you
If you need the handler to be called on a null I have a pull request for a solution on the following issue which may be of use to you https://github.com/DapperLib/Dapper/issues/1754
Of course your problem maybe something else completely :D or you might not need the handler to react, you might just be looking for the reason why it wasn’t called.
Good luck - let us know how you get on.
When I did my initial development, I was using Dapper.Fsharp on top so it was a little hard to diagnose. I've done a few experiments this week using just plain dapper.
As far as I can tell, the SetValue override does not ever get called when using the PrimaryKey type as defined above - regardless of whether it is empty or has a value. The TypeHandler is properly registered, and the .Parse override does work. When trying to pass a PrimaryKey type to a query, it fails with:
The member param1 of type Project.Types+PrimaryKey`1 ... cannot be used as a parameter value