How to Update Multiple Fields from an Object with FSharp.Data.SqlClient

Question

I've been looking into F# in relation to CRUD with data . and I have been using FSharp.Data.SqlClient

I can't see an easy way to update all fields from an object.

For example I want to execute the code below - and then I want to present that data to a web page. The web page will make some changes ( maybe ) - then I want to use the object to update the database.

I don't want to have to write code to map every single field. Additionally, I am still trying to get my head around how this is done in an immutable way.

let getOrders2() = 
 let cmd = new SqlCommandProvider<"
 SELECT top 10 * from orders
 " , connectionString>(connectionString)
 let orders = cmd.Execute()
 let o2 = orders |> Seq.toList

• Scott Hutchinson: Consider using Dapper: github.com/Dzoukr/Dapper.FSharp#update
• Martin Thompson: @ScottHutchinson Thanks - but I think you have to define all the F# objects in Dappa? that seems a bit cumbersome if you don't have to ..

Answer 1

Updating multiple fields at once from an object is straightforward:

let updateEmployee employee =
 use cmd =
 new SqlCommandProvider<
 "update Employees set \
 FirstName = @FirstName,
 LastName = @LastName
 where EmployeeID = @EmployeeID",
 connectionString>(connectionString)
 let nRows =
 cmd.Execute(
 employee.FirstName,
 employee.LastName,
 employee.EmployeeID)
 assert(nRows = 1)

Writing a web app with immutable objects is a big topic. Are you using F# just on the server, or also in the client?

• Martin Thompson: thank you . F# on the server - expose DAL through Rest API. Vuejs on the client ( Quasar to be specific ) I wanted to avoid having to set every single field - some of my tables have quite a few fields in them. Is there an easy way to do that in this framework?
• Brian Berns: You could have different update statements that set only the fields needed for each use case. Or you could write and call a general-purpose stored proc that consumes XML (or JSON) instead of executing a SQL update statement directly. It depends on how creative you want to get.
• Martin Thompson: thanks, I guess I want to only update the fields that have changed. So I would somehow need to iterate the object properties and compare them I guess..?
• Brian Berns: You can do that, but in my experience it's almost always more trouble than it's worth. In a typical "CRUD" app, it's better to have a single "dirty" flag at the object level, rather than tracking at the property level. You can optimize later if necessary. Just my opinion.