F# and Excel integration for .NET 4.0 (Visual Studio 2010 Beta 1)

The Problem (Q-score 3, ranked #157th of 303 in the Excel VBA archive)

The scenario as originally posted in 2009

Can anyone give a web link to or demonstrate here how to do F# and Excel integration using .NET 4.0 (Visual Studio 2010 Beta 1)?

I know how to do this in the CTP release but as far as I know it should be simpler in .NET 4.0 (Visual Studio 2010 Beta 1).

Why this Range / Worksheet targeting trips people up

The question centers on reaching a specific cell, range, or workbook object. In Excel VBA, this is the #1 source of failures after activation events: every property (.Value, .Formula, .Address) behaves differently depending on whether the parent Workbook is explicit or implicit.

The Verified Solution — solid answer (above median) (+12)

48-line Excel VBA pattern (copy-ready)

There is no ‘secret sauce’ added to the latest F# CTP release (Visual Studio 2010 Beta1) to improve Office interop. Perhaps you have F# confused with C#’s new support for Dynamic.

However, Office interop in F# is the same as C# – you can use the native COM APIs or the newer, managed Visual Studio Tools for Office (VSTO) libraries. Unfortunately F# doesn’t have the UI-designers for creating VSTO add-ins like C#, so the simplest way to do Office interop is to use the COM APIs.

The following snippet creates an Excel worksheet with information about the pictures in your My Pictures folder:

#r "Microsoft.Office.Interop.Excel"

open System
open System.IO
open System.Reflection
open Microsoft.Office.Interop.Excel


let app = ApplicationClass(Visible = true)


let sheet = app.Workbooks
               .Add()
               .Worksheets.[1] :?> _Worksheet


let setCellText (x : int) (y : int) (text : string) = 
    let range = sprintf "%c%d" (char (x + int 'A')) (y+1)
    sheet.Range(range).Value(Missing.Value) <- text


let printCsvToExcel rowIdx (csvText : string) =
    csvText.Split([| ',' |])
    |> Array.iteri (fun partIdx partText -> setCellText partIdx rowIdx partText)


let rec filesUnderFolder basePath = 
    seq {
        yield! Directory.GetFiles(basePath)
        for subFolder in Directory.GetDirectories(basePath) do
            yield! filesUnderFolder subFolder 
    }


// Print header
printCsvToExcel 0 "Directory, Filename, Size, Creation Time"


// Print rows
filesUnderFolder (Environment.GetFolderPath(Environment.SpecialFolder.MyPictures))
|> Seq.map (fun filename -> new FileInfo(filename))
|> Seq.map (fun fileInfo -> sprintf "%s, %s, %d, %s" 
                                fileInfo.DirectoryName 
                                fileInfo.Name 
                                fileInfo.Length 
                                (fileInfo.CreationTime.ToShortDateString()))
|> Seq.iteri (fun idx str -> printCsvToExcel (idx + 1) str)

When to Use It — vintage (14+ years old, pre-2013)

Ranked #157th in its category — specialized fit

This pattern sits in the 96% tail relative to the top answer. Reach for it when your scenario closely matches the question title; otherwise browse the Excel VBA archive for a higher-consensus alternative.

What changed between 2009 and 2026

The answer is 17 years old. The Excel VBA object model has been stable across Office 2013, 2016, 2019, 2021, 365, and 2024/2026 LTSC, so the pattern still compiles. Changes that might affect you: 64-bit API declarations (use PtrSafe), blocked macros in downloaded files (Mark-of-the-Web), and the shift toward Office Scripts for web-first workflows.