MultiExec is not supported by ExecuteReader

Question

I have the following code:

let getByIdAsync (connectionString : string) (id : int) = 
        let sql = @"SELECT * FROM [User] WHERE [Id] = @id"
        let args = [ "id" => id ]

        async {
            use connection = new SqlConnection(connectionString)
            do! connection.OpenAsync() |> Async.AwaitTask

            try
                use! reader = connection.ExecuteReaderAsync(sql, args) |> Async.AwaitTask
                return reader |> mapRowsToRecords |> Seq.head
            with
            | e -> return Error e.Message
        }

This code throws MultiExec is not supported by ExecuteReader and I have no idea why. Other queries (like my insert for example) work just fine. What am I doing wrong?

Possible [dup](https://stackoverflow.com/questions/52410794/getting-multiexec-is-not-supported-by-executereader-when-running-an-spr). — Dan Guzman, Jun 19 '21 at 22:19
Nope, I already looked at that one, don't get it, I don't see how I got multiple exec in my case. I only have one query. — vladek, Jun 19 '21 at 22:22
I'm not sure this is the issue, but you invoke `OpenAsync` and then ignore the result, meaning that `ExecuteReaderAsync` could, in principle, be started before the connection is (fully) open. You should use `do!` with `OpenAsync`. — Tomas Petricek, Jun 19 '21 at 23:26
@TomasPetricek Thank you, nice catch! I'm learning F# and was looking for a way to do `await OpenAsync()` so I was trying all sorts of hacks. Unfortunately, this does not solve the issue, but will update the code in the question. — vladek, Jun 19 '21 at 23:36

vladek · Accepted Answer · 2021-06-20T00:07:32.443

I know what's wrong, missing dict before the dictionary:

let getByIdAsync (connectionString : string) (id : int) = 
        let sql = @"SELECT * FROM [User] WHERE [Id] = @id"
        let args = dict [ "id" => id ] // added dict

        async {
            use connection = new SqlConnection(connectionString)
            do! connection.OpenAsync() |> Async.AwaitTask

            try
                use! reader = connection.ExecuteReaderAsync(sql, args) |> Async.AwaitTask
                return reader |> mapRowsToRecords |> Seq.head
            with
            | e -> return Error e.Message
        }

Check this article for more info.

MultiExec is not supported by ExecuteReader

1 Answers1