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@vbfox
Last active April 21, 2022 02:58
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Minimal dapper in F#
module DapperFSharp =
open System.Data.SqlClient
open System.Dynamic
open System.Collections.Generic
open Dapper
let dapperQuery<'Result> (query:string) (connection:SqlConnection) =
connection.Query<'Result>(query)
let dapperParametrizedQuery<'Result> (query:string) (param:obj) (connection:SqlConnection) : 'Result seq =
connection.Query<'Result>(query, param)
let dapperMapParametrizedQuery<'Result> (query:string) (param : Map<string,_>) (connection:SqlConnection) : 'Result seq =
let expando = ExpandoObject()
let expandoDictionary = expando :> IDictionary<string,obj>
for paramValue in param do
expandoDictionary.Add(paramValue.Key, paramValue.Value :> obj)
connection |> dapperParametrizedQuery query expando
type User = { UserId:string }
let getUsers connection =
connection
|> dapperQuery<User> "SELECT UserID From tbUser"
let getUser userId connection =
connection
|> dapperMapParametrizedQuery<User> "SELECT UserID From tbUser WHERE UserId = @UserId" (Map ["UserId", userId])
|> Seq.head
type UserSelectArgs = { SelectedUserId:string}
let getUser' userId connection =
connection
|> dapperParametrizedQuery<User> "SELECT UserID From tbUser WHERE UserId = @SelectedUserId" {SelectedUserId=userId}
|> Seq.head
@matthewblott
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This looks useful. I'm trying to port a C# Dapper library using the Unit of Work pattern which is how I ended up here. What's missing (for me) is a way to wrap this up with transactions.

@nobleach
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nobleach commented Mar 18, 2018

Definitely would be a plus to add the "chrome" around these snippets. They're very helpful. New users can add

open System.Data.SqlClient
open Dapper
open Npgsql

let connString = "Host=localhost;Database=exampleDB;Username=postgres;Password=example"
let connection = new NpgsqlConnection(connString)
connection.Open()

Note: You'll also need to install Npgsql: dotnet add package Npgsql --version 3.2.7 if you're using Postgres, like I am.

@mtrsk
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mtrsk commented Jun 8, 2018

Many thanks @vbfox & @nobleach, the script works and saved me hours of frustration!

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