Stateモナドでコネクション管理

これは結構使える！かも。

open System

open System.Transactions

open FSharp.Monad.State

open Soma.Core
let config = 

  { new MsSqlConfig() with

    member this.ConnectionString = "Data Source=.;Initial Catalog=Soma.Tutorial;Integrated Security=True" }
let getConnection() = state {

  let! conOption = getState

  let con =

    match conOption with

    | Some con -> con

    | _ -> LocalDb.createConnection config

  do! putState (Some con)

  return con }
let find<'T when 'T : not struct> id = state { 

  let! con = getConnection()

  return LocalDb.find<'T> config con id }
let insert<'T when 'T : not struct> entity = state { 

  let! con = getConnection()

  return LocalDb.insert<'T> config con entity }
let update<'T when 'T : not struct> entity = state { 

  let! con = getConnection()

  return LocalDb.update<'T> config con entity }
let delete<'T when 'T : not struct> entity = state { 

  let! con = getConnection()

  LocalDb.delete<'T> config con entity }
let requiredTx m = 

  use tx = new TransactionScope(TransactionScopeOption.Required)

  let result = eval m None

  tx.Complete()

  result
type Employee = 

  { [<Id(IdKind.Identity)>]

    EmployeeId : int 

    EmployeeName : string

    DepartmentId : int

    [<Version>]

    VersionNo : int }
let exec2 emp = state {

  do! delete emp }
let exec() = state {

  let! emp = insert { EmployeeId = 0; EmployeeName = "Allen"; DepartmentId = 2; VersionNo = 0}

  let! emp = find<Employee> [emp.EmployeeId]

  let! emp = update { emp with EmployeeName = "Hoge" }

  do! exec2 emp

  return emp }
exec() 


    

    
> requiredTx
    
    

    
> printfn "%A"
    
Console.ReadKey() |> ignore