F# and ADO.NET - idiomatic F#

I'm just starting to learn F#. I wrote this F#/ADO.NET code last night. In what ways would you improve the syntax - make it feel like idiomatic F#?

    let cn = new OleDbConnection(cnstr)
    let sql = "SELECT * FROM People"
    let da = new OleDbDataAdapter(new OleDbCommand(sql, cn))
    let ds = new DataSet()
    cn.Open()
    let i = da.Fill(ds)
    let rowCol = ds.Tables.[0].Rows
    let rowCount = rowCol.Count
    printfn "%A" rowCount

    for i in 0 .. (rowCount - 1) do
        let row:DataRow = rowCol.[i]
        printfn "%A" row.["LastName"]

Note: I did find the syntax checker did not like rowCol.[i].["LastName"] What is the proper way to handle dual-indexers? I had to break up the code over two lines.

Also If I hadn't gone down the DataSet route and used a SqlDataReader that loaded its data into F# records. What collection structure should I use for containing the records? The standard .NET List<>?