run-time connection string configuration for multiple data sources

[fsprojects]

run-time connection string configuration for multiple data sources

[vasily-kirichenko]

I used static method because I didn't know it's possible to constrain on arbitrary constructor, not only on unit -> ^a. So, your solution is obviously better.

What about your main question, I really have no good ideas :( The best I managed to make is following:

module Settings = 
    let DB1ConnectionString = ""
    let DB2ConnectionString = ""

let inline create connStr : ^a = (^a : (new : string -> ^a) connStr)  

module DB1 =
    type Command11 (connString: string) = class end
    type Command12 (connString: string) = class end
    let inline create() = create Settings.DB1ConnectionString

module DB2 =
    type Command21 (connString: string) = class end
    type Command22 (connString: string) = class end
    let inline create() = create Settings.DB2ConnectionString

let cmd11 : DB1.Command11 = DB1.create()
let cmd12 : DB1.Command12 = DB1.create()
let cmd21 : DB2.Command21 = DB2.create()
let cmd22 : DB2.Command22 = DB2.create()

However, it's convention only. Nothing stops us to use wrong runtime connection strings :(

We need parameterized modules :) Or nested types :)

[dmitry-a-morozov]

Fixed in release 1.1.27.
In latest release command type gets static property called "ConnectionStringOrName" with value same as passed down to the type provider at design time. So now example of factory above can be update to

module Settings = 
    [<Literal>]
    let DB1ConnectionString = ""
    [<Literal>]
    let DB2ConnectionString = ""

module SqlCommand = 
    type Command1  = SqlCommand<"SELECT * ...", DB1ConnectionString >
    type Command2  = SqlCommand<"SELECT * ...", DB2ConnectionString >

    let inline create() : 'a = 
        let designTimeConnectionString = (^a : (static member get_ConnectionStringOrName : unit -> string) ())

           // i'll skip dot (.) int "ConnectionStrings.["DB1"]" because github code in-lining freaks out
            let db1ConnStr = ConfigurationManager.ConnectionStrings["DB1"].ConnectionString
            let db2ConnStr = ConfigurationManager.ConnectionStrings["DB2"].ConnectionString

        match designTimeConnectionString  with
        | DB1ConnectionString  -> (^a : (new : string -> ^a) db1ConnStr )    
        | DB2ConnectionString  -> (^a : (new : string -> ^a) db2ConnStr )    
        | _ -> failwithf "Unrecognized command type %s" typeof<'a>.FullName

(*
       or even
        let database = SqlConnectionStringBuilder(designTimeConnectionString).InitialCatalog
        if database = "AdventureWorks2012"
        then 
            (^a : (new : string -> ^a) adventureWorks)    
        else failwithf "Unrecognized command type %s" typeof<'a>.FullName
*)

Feedback on this new feature is welcomed.

[dmitry-a-morozov]

@vasily-kirichenko How do you like this new design?