I am writing an application in F#/WPF called Photograph. They are problem with Thread.Sleep(1000). When I called let goIt fileName, I get blank image and then full image. How do I get image with one second visible?

Here the case:

let mutable fileIt = false

let goIt fileName =

txtLog.AppendText(fileName + "\r")

let directory = fileName.Substring(0, fileName.LastIndexOf(@"\") + 1)

let dir = new DirectoryInfo(directory)

let picture = fileName.Substring(fileName.LastIndexOf(@"\") + 1)

let ext = fileName.Substring(fileName.LastIndexOf(@".jpg"))

fileIt <- false

for file in dir.GetFiles() do

if picture = (string) file then

txtLog.AppendText(

fileName.Substring(fileName.LastIndexOf(@"\") + 1) + "\r")

fileIt <- true

elif fileIt = true then

let s = (string) file

let s = s.ToLower()

if ext = s.Substring(s.Length - 4) then

txtLog.AppendText((string) file + "\r")

loadImages (directory + s)

stack.Children.Remove(image)

stack.Children.Add(image) |> ignore

Thread.Sleep(1000)

btnGo.Click.Add(fun _ -> goIt @"D:\Images\Orchids-000.jpg")