F# version of https://stackoverflow.com/a/19538654/68086

Log4netSetup.fs

open log4net.Appender
open log4net.Core
open log4net.Layout
open log4net.Repository.Hierarchy

let setup () : unit =
    let hierarchy     = LogManager.GetRepository() :?> Hierarchy
    let patternLayout = PatternLayout()
    patternLayout.ConversionPattern <- "%date [%thread] %-5level %logger - %message%newline"
    patternLayout.ActivateOptions()

    let roller = RollingFileAppender()
    roller.AppendToFile       <- false
    roller.File               <- @"Logs\EventLog.txt"
    roller.Layout             <- patternLayout
    roller.MaxSizeRollBackups <- 5
    roller.MaximumFileSize    <- "1GB"
    roller.RollingStyle       <- RollingFileAppender.RollingMode.Size
    roller.StaticLogFileName  <- true
    roller.ActivateOptions()
    hierarchy.Root.AddAppender(roller)

    let memory = MemoryAppender()
    memory.ActivateOptions()
    hierarchy.Root.AddAppender(memory)

    hierarchy.Root.Level <- Level.Info
    hierarchy.Configured <- true