basic CRUD example in giraffe based on https://blogs.msdn.microsoft.com/dotnet/2017/09/26/build-a-web-service-with-f-and-net-core-2-0/

CRUD_example.fs

namespace CRUDSample

open System.IO
open NPoco
open Microsoft.Data.Sqlite

type LunchSpot() = 
    member val ID = 0 with get, set
    member val Name = "" with get, set
    member val Latitude = 0.0 with get, set
    member val Longitude = 0.0 with get, set
    member val Cuisine = "" with get, set
    member val VegetarianOptions = false with get, set
    member val VeganOptions = false with get, set


module LunchAccess =
    let private connString = "Filename=" + Path.Combine(Directory.GetCurrentDirectory(), "Sample.db")

    let private getLunchFetchingQuery filter =

        let cuisinePart, hasCuisine =
            match filter.Cuisine with
            | Some c -> (sprintf "Cuisine = \"%s\"" c, true)
            | None -> ("", false)

        let vegetarianPart, hasVegetarianPart =
            match filter.VegetarianOptions with
            | Some v -> (sprintf "VegetarianOptions = \"%d\"" (if v then 1 else 0), true) // Sqlite uses ints 0 and 1 for bools.
            | None -> ("", false)

        let veganPart, hasVeganPart =
            match filter.VeganOptions with
            | Some v -> (sprintf "VeganOptions = \"%d\"" (if v then 1 else 0), true) // Sqlite uses ints 0 and 1 for bools.
            | None -> ("", false)

        if hasCuisine || hasVegetarianPart || hasVeganPart then 
            "where " + cuisinePart +
            (if hasCuisine && hasVegetarianPart then " and " + vegetarianPart else vegetarianPart) +
            (if (hasCuisine || hasVegetarianPart) && hasVeganPart then " and " + veganPart else veganPart)
            |> Some
        else
            None
    let getLunches (filter: LunchFilter) =

        use db = new Database(connString)

        match getLunchFetchingQuery filter with
        | Some query -> db.Fetch<LunchSpot>(query)
        | None       -> db.Fetch<LunchSpot>()
    
    let createLunch (lunchSpot: LunchSpot) =
        let db = new Database(connString)
        db.Insert(lunchSpot)
    let updateLunch (lunchSpot: LunchSpot) =
        use db = new Database(connString)
        db.Update(lunchSpot)
    let deleteLunch (lunchSpot: LunchSpot) =
        use db = new Database(connString)
        db.Delete(lunchSpot)

let webApp = 
    choose [
        route "home" >=> text "You're Home!!"
        route "/lunchspot" >=> choose [
            GET >=> (fun next ctx -> 
                let filter = ctx.BindQueryString<LunchFilter>()
                let lunchSpots = LunchAccess.getLunches filter
                json lunchSpots next ctx
            )
            POST >=> (fun next ctx -> task {
                let! lunch = ctx.BindJson<LunchSpot>()
                LunchAccess.createLunch lunch
                return! text (sprintf "Added %s to the lunch spots." lunch.Name) next ctx
            })
            PUT >=> (fun next ctx -> task {
                let! lunch = ctx.BindJson<LunchSpot>()
                LunchAccess.updateLunch lunch
                return! text (sprintf "updated %s in lunch spots." lunch.Name) next ctx
            })
            DELETE >=> (fun next ctx -> task {
                let! lunch = ctx.BindJson<LunchSpot>()
                LunchAccess.deleteLunch lunch
                return! text (sprintf "dleted %s from lunch spots." lunch.Name) next ctx
            })
        ]
    ]