F # Assigning a function return value to an object using microsoft odbc

Question

in VB I have this code,

Dim dataset As System.Data.Odbc.OdbcDataReader = cmd.ExecuteReader()

which creates an object with the results of cmd.Execute Reader of type OdbcDataReader and assigns it to a dataset. cmd is a System.Data.Odbc.OdbcCommand object.

In f # I tried

let  dataset = new System.Data.Odbc.OdbcDataReader
    dataset <- cmd.ExecuteReader

as well as a mutable version of the dataset, I also tried

let dataset = cmd.ExecuteReader

The first errors in the second instance of the dataset, saying: "Incomplete structured construction at or to this point in the expression," adding a semicolon does not help.

Second error on let; saying that the expression is not complete. How to create an object with the result of System.Data.Odbc.OdbcCommand.ExecuteReader?

edit:

More code

let dataConnection = new System.Data.Odbc.OdbcConnection()
dataConnection.ConnectionString <- "*******"
let mystring = "SQL query"

let cmd = new System.Data.Odbc.OdbcCommand(mystring, dataConnection)
let odbcConnectFunction = 

    try
        dataConnection.Open()
        System.Console.WriteLine "connected"
        //let  dataset = new System.Data.Odbc.OdbcDataReader
        let dataset = cmd.ExecuteReader()
    finally
    dataConnection.Close()

Answer 1

cmd OdbcCommand , , OdbcCommand.ExecuteReader , " ":

let dataset = cmd.ExecuteReader()

cmd DbCommand, .

VB , (OdbcDataReader), DbDataReader OdbcDataReader. F # .

F #:

let dataset = cmd.ExecuteReader() :?> System.Data.Odbc.OdbcDataReader