WPF window will not open after adding namespace - wpf

Question

So I have simple F# WPF application. It was working just fine without declaring a namespace and using multiple modules.
Now, it still compiles, but simply does nothing. Nothing in debug to show either.
This is the current code that does not work.
namespace Flow
module MainApp =
open System
open System.Windows
let app1 = new Application()
[<STAThread>]
app1.Run(new Main.MainWindow()) |>ignore
before it worked when it was like this
module MainApp
open System
open System.Windows
let app1 = new Application()
[<STAThread>]
app1.Run(new Main.MainWindow()) |>ignore
I can show the definition of MainWindow, but its very long, its a class that inherits from Window.
Let me know if that would help. Or if there is anything other information that I could give that would help with this issue.

Answer 1

Your original code relies on an implicit entry point:
"When a program has no EntryPoint attribute that explicitly indicates the entry point, the top level bindings in the last file to be compiled are used as the entry point."
You can either define a function in your module and explicitly mark that as the entry point:
namespace Flow
module MainApp =
open System
open System.Windows
let app1 = new Application()
[<EntryPoint>]
[<STAThread>]
let main args =
app1.Run(new Window())
Or you can continue to use an implicit entry point by including the namespace in the module name:
module Flow.MainApp
open System
open System.Windows
let app1 = new Application()
[<STAThread>]
app1.Run(new Window()) |>ignore