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The Browse For Folder Dialog Box

 

Introduction to the Browse For Folder Dialog Box

 

Description

The Save and Open dialog boxes allow a user to save or open files only. Microsoft Windows provides a dialog box specially made so that a user can select a folder if an application needs one for any reason a programmer judges necessary. This dialog box appears as follows:

The Browse For Folder Dialog Box

When this dialog box comes up, it displays the Desktop folder as the parent and all the other folders can be located from it. To use it, the user can click one of the folders or drives and click OK. If the desired folder is not seen but is available, the user can expand the existing folders and drives, click the desired folder, and click OK. If the necessary folder is not available at all, the user can first select an existing folder or drive, click the Make New Folder button, type a name for the new folder, and click OK.

Besides the folders, the Browse For Folder dialog box also allows the user to navigate to folders or directories of the network.

Creating a Browse For Folder Dialog Box

The Browse For Folder dialog box is made available through the FolderBrowserDialog class that is derived from the CommonDialog class:

type FolderBrowserDialog =  
    class 
        inherit CommonDialog 
    end

To initiate this dialog box, you can declare a variable of type FolderBrowserDialog, use the new operator to allocate memory for it by calling its default constructor. Here is an example:

let fbd = new FolderBrowserDialog()

Displaying a Browse For Folder Dialog Box

To display the Browse For Folder dialog box, call its ShowDialog() method. Here is an example:

open System
open System.Windows.Forms

let exercise : Form = new Form()

let fbd = new FolderBrowserDialog()

fbd.ShowDialog() |> ignore

[<STAThread>]
[<EntryPoint>]
let main argv = 
    Application.Run exercise
    0
 
   
 

Characteristics of the Browse For Folder Dialog Box

 

The Description

By default, and as seen on the above screenshot, the Browse For Folder dialog box doesn't indicate what it is used for. This is because it is left up to you to let the user know what you expect. To provide this information, the Browse For Folder dialog box is equipped with a label that can be made visible or not. It is available through the Description property:

member Description : string with get, set

If you provide a string for this property, it would display under the title bar but above the tree view of the dialog box. Here is an example of specifying a label for the dialog box:

open System
open System.Windows.Forms

let exercise : Form = new Form()

let fbd = new FolderBrowserDialog()
fbd.Description <- "Select the directory where your future configurations will be installed"

fbd.ShowDialog() |> ignore

[<STAThread>]
[<EntryPoint>]
let main argv = 
    Application.Run exercise
    0

This would produce:

The Browse For Folder dialog box with an indicative label

The Root Folder

As you can see from this screenshot, when the dialog box comes up, it selects the Desktop, by default, as the parent folder. If you want, you can specify a different default folder to be selected. This information is carried by the RootFolder property:

member RootFolder : Environment.SpecialFolder with get, set

The RootFolder value must be a member of the SpecialFolder enumeration of the Environment class. For example, to select My Documents, you would type the following:

open System
open System.Windows.Forms

let exercise : Form = new Form()

let fbd = new FolderBrowserDialog()
fbd.Description <- "Select the directory where your future configurations will be installed"

fbd.RootFolder <- Environment.SpecialFolder.Personal

fbd.ShowDialog() |> ignore

[<STAThread>]
[<EntryPoint>]
let main argv = 
    Application.Run exercise
    0

This would produce:

The Selected Path

Since there is only a limited number of folders of the SpecialFolder enumerator, you may want to specify a different folder. The advantage of the SpecialFolder option is that it is likely to be found on the user's computer. If you know for sure that a certain folder exists on the computer and you would rather select that folder, you can provide its complete path. To support this, he class is equipped with property named SelectedPath:

member SelectedPath : string with get, set

Here is an example:

open System
open System.Windows.Forms

let exercise : Form = new Form()

let fbd = new FolderBrowserDialog()
fbd.Description <- "Select the directory where your future configurations will be installed"

fbd.SelectedPath <- @"C:\Programs\Corporate"

fbd.ShowDialog() |> ignore

[<STAThread>]
[<EntryPoint>]
let main argv = 
    Application.Run exercise
    0

This would produce;

Browse For Folder

You should not specify both the RootFolder and the SelectedPath properties on the same FolderBrowserDialog control.

After the user has used the Browse For Folder dialog box, has selected a folder, and clicked OK, to find out what folder the user selected, get the value of the SelectedPath property.

The Make New Folder Button

After using the Browse For Folder dialog box, the user may select a folder and click OK. Imagine you are creating a commercial application, you can't possibly know the content of every customer's computer. This means that there is a possibility that the user would not find the desired folder. One solution you can use is to give users the ability to create a new folder. This option is available by default. If you want to prevent the user from creating a new folder, hide the Make New Folder button. To support this, the class is equipped with a Boolean property named ShowNewFolderButton:

member ShowNewFolderButton : bool with get, set

Here is an example:

open System
open System.Windows.Forms

let exercise : Form = new Form()

let fbd = new FolderBrowserDialog()
fbd.Description <- "Select the directory where your future configurations will be installed"

fbd.ShowNewFolderButton <- false

fbd.ShowDialog() |> ignore

[<STAThread>]
[<EntryPoint>]
let main argv = 
    Application.Run exercise
    0

This would produce:

The Browse For Folder dialog box without the Make New Folder button

You can also check the value of the ShowNewFolderButton property to find out whether the dialog box is equipped with a Make New Folder button.

 
 
   
 

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