open System.Windows.Forms

Question

Why does

open System.Windows.Forms

work in the immediate F# window but gives an error in the edit window

Answer 1

Could you please clarify a litle bit more what error do you get? Does your project refer to System.Windows.Form.dll. Do you have #r "System.Windows.Forms.dll" directive in your immediate window?

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Petr

Answer 2

Type

open System.Windows.Forms

in the Edit window. The wavy red line appears under Windows.

Hover the mouse pointer over Windows.

The error message "The namespace 'Windows' is not defined" appears

Answer 3

You probably need to add reference to System.Windows.Forms to your project

---

Petr

Answer 4

Thank you, that has solved the problem.

THe book Programming F# by O'Reilly doesnt mention setting up references, so thank you very much

Henry

Answer 5

I don't have the book here right now but I think it was mentioned somewhere.

Anyhow: those books tend to be written for people already familiar with .NET and references, namespaces. etc. is the same in any core-language (C#/VB.net/F#) so it might be missing.

But if you read the online-documentation for open (Import Decleratiopns: The open Keyword) you will find all this wonderful explained - so the first thing you should look for is msdn or a simple google search ;)

Right from the MSDN:

"The module or namespace provided must be in the same project or in a referenced project or assembly. If it is not, you can add a reference to the project, or use the -reference command-line option (or its abbreviation, -r). For more information, see Compiler Options (F#)."