A simple MSBuild task in F# to calculate the MD5 hash of a file

namespace MSBuild.Tasks

open System
open System.IO
open System.Security.Cryptography
open Microsoft.Build.Utilities
open Microsoft.Build.Framework

type Md5Sum() =
    inherit Task()

    let mutable inputFile = ""

    let mutable md5Value = ""

    [<Required>]
    member this.InputFile
        with get() = inputFile
        and set(v) = inputFile <- v

    [<Output>]
    member this.Md5Value
        with get() = md5Value
        and set(v) = md5Value <- v

    override this.Execute() = 
        let resultCode =
            try
                base.Log.LogMessage(MessageImportance.Normal, "Computing MD5 hash for {0}", inputFile)
                let md5csp = MD5CryptoServiceProvider.Create()
                let md5Value = inputFile |> File.ReadAllBytes |> md5csp.ComputeHash |> Convert.ToBase64String
                base.Log.LogMessage(MessageImportance.Normal, "Computed MD5 hash is {0}", md5Value.ToString())
                true
            with
                | _ as ex -> base.Log.LogErrorFromException(ex, false); false
        resultCode