Check box, Radio button, and Group box in Visual F#'s Windows Form Application

One of the most commonly used form controls in real-life application is the check box. A check box is a control that allows user to select various options from a group of options. To create a check box in Visual F#, use the following syntax:

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1. let checkboxobjvariable=new CheckBox()  

let checkboxobjvariable=new CheckBox()

For instance:

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1. let chk=new CheckBox()  

let chk=new CheckBox()

Some of the essential properties of check box are Text and Checked. The Text property enables user to add a text beside a check box while the Checked property checks or unchecks a check box and can handle the boolean value true or false. Visual F#’s check box shares the same properties with the check boxes in other visual programming languages such as Visual C++, Visual J# and Visual Basic, so if you want to learn its other properties, check the check box properties of other visual programming languages.

Radio button of the other hand, is the complete opposite of check box for the fact that it only allow a single selection among a list of options. To change the text beside the radio button, use the Text property. It also has a Checked property which enables user to tick or untick the radio button.

To create a radio button, use the following syntax:

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1. let radiobuttonobjvariable=new RadioButton()  

let radiobuttonobjvariable=new RadioButton()

For example:

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1. let rdo=new RadioButton()  

let rdo=new RadioButton()

To group check boxes and radio buttons, a control called group box is used. Though there are several properties of radio buttons, the most frequently used is the Text property and is used to change the group box header text. To create a group box, use the following syntax:

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1. Let groupboxobjvariable=new GroupBox()  

Let groupboxobjvariable=new GroupBox()

For instance:

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1. Let grp=new GroupBox()  

Let grp=new GroupBox()

Let’s now use the check box, radio button, and group box in a single application. Just follow these steps:

1. Click Start>All Programs>Microsoft Visual Studio 2008>Microsoft Visual Studio 2008.

2. Click File>New>Project>Select Visual F# in the project types>Select F# application in the Visual Studio installed templates category.

3. Click the Project menu>Add reference>Click the .Net tab>Locate then double-click System.Windows.Forms.
Do step 3 again and this time, select System.Drawing

4. Enter the following code after the line “// Learn more about F# at http://fsharp.net “:

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1. // Learn more about F# at http://fsharp.net  
2. //use the Visual F# library  
3. open System  
4. //use System.Drawing  
5. open System.Drawing  
6. //specifies the location of the Form classes  
7. open System.Windows.Forms  
8. //creates a form named cnbform and assign a “Use Radio Button” caption to it  
9. let cnbform=new Form(Text="Use Radio Button",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)  
10. //creates a group box and sets its header text to “RadioButtons”  
11. //Use the Top and Left properties to align it in the form  
12. let gbox1=new GroupBox(Text="RadioButtons", Location=new System.Drawing.Point(10,5),Height=80)  
13. //creates a radio button and change its text to “First radio button”  
14. //Use the top and left property to align it in the group box  
15. let radio1=new RadioButton(Text="First radio button", Location=new System.Drawing.Point(20,20),AutoSize=true)  
16. //creates radio button and set its text to “Second radio button”  
17. //Use the autosize property to automatically expand the width of text handler  
18. let radio2=new RadioButton(Text="Second radio button", Location=new System.Drawing.Point(20,40),AutoSize=true)  
19. //creates a group box and set its text to “CheckBoxes”  
20. //position the group box in the form by using the Top and Left properties  
21. let gbox2=new GroupBox(Text="CheckBoxes",Height=80, Location=new System.Drawing.Point(10,100))  
22. //creates a check box and change its text to “First checkbox”  
23. //Use the top and left property to align it in the group box  
24. let check1=new CheckBox(Text="First checkbox", Location=new System.Drawing.Point(20,20),AutoSize=true)  
25. //creates another check box and change its text to “Second checkbox”  
26. //Use the top and left property to align it in the group box  
27.   
28. let check2=new CheckBox(Text="Second checkbox", Location=new System.Drawing.Point(20,40),AutoSize=true)  
29. //creates a button and set its text to “Exit”  
30. let exitbutton=new Button(Location=new System.Drawing.Point(200,200),Text="Exit")  
31.   
32. //displays the first group box into the form  
33. cnbform.Controls.Add(gbox1)  
34. //adds the radio buttons into the groupbox  
35. gbox1.Controls.Add(radio1)  
36. gbox1.Controls.Add(radio2)  
37.   
38. //adds the second group box into the form  
39. cnbform.Controls.Add(gbox2)  
40. //displays the checkboxes into the second groupbox  
41. gbox2.Controls.Add(check1)  
42. gbox2.Controls.Add(check2)  
43.   
44. //inserts the exit button into the form  
45. cnbform.Controls.Add(exitbutton)  
46. //attach a click event to the first radio button then assign a function to it  
47. radio1.Click.Add(fun r1msg->  
48. //check the first checkbox  
49. check1.Checked<-true  
50.                //unchecks the first checkbox  
51.                 check2.Checked<-false)  
52.   
53. //attach a click event to the first radio button then assign a function to it  
54.   
55. radio2.Click.Add(fun r2msg->  
56. //check the second checkbox  
57. check2.Checked<-true  
58.               //unchecks the first checkbox  
59.               check1.Checked<-false)  
60. //quits the form when the exit button is clicked                   
61. exitbutton.Click.Add(fun bact->cnbform.Close())      
62. //shows the form         
63. cnbform.Show()  
64. //runs the application  
65. Application.Run(cnbform)  

// Learn more about F# at http://fsharp.net
//use the Visual F# library
open System
//use System.Drawing
open System.Drawing
//specifies the location of the Form classes
open System.Windows.Forms
//creates a form named cnbform and assign a “Use Radio Button” caption to it
let cnbform=new Form(Text="Use Radio Button",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)
//creates a group box and sets its header text to “RadioButtons”
//Use the Top and Left properties to align it in the form
let gbox1=new GroupBox(Text="RadioButtons", Location=new System.Drawing.Point(10,5),Height=80)
//creates a radio button and change its text to “First radio button”
//Use the top and left property to align it in the group box
let radio1=new RadioButton(Text="First radio button", Location=new System.Drawing.Point(20,20),AutoSize=true)
//creates radio button and set its text to “Second radio button”
//Use the autosize property to automatically expand the width of text handler
let radio2=new RadioButton(Text="Second radio button", Location=new System.Drawing.Point(20,40),AutoSize=true)
//creates a group box and set its text to “CheckBoxes”
//position the group box in the form by using the Top and Left properties
let gbox2=new GroupBox(Text="CheckBoxes",Height=80, Location=new System.Drawing.Point(10,100))
//creates a check box and change its text to “First checkbox”
//Use the top and left property to align it in the group box
let check1=new CheckBox(Text="First checkbox", Location=new System.Drawing.Point(20,20),AutoSize=true)
//creates another check box and change its text to “Second checkbox”
//Use the top and left property to align it in the group box

let check2=new CheckBox(Text="Second checkbox", Location=new System.Drawing.Point(20,40),AutoSize=true)
//creates a button and set its text to “Exit”
let exitbutton=new Button(Location=new System.Drawing.Point(200,200),Text="Exit")

//displays the first group box into the form
cnbform.Controls.Add(gbox1)
//adds the radio buttons into the groupbox
gbox1.Controls.Add(radio1)
gbox1.Controls.Add(radio2)

//adds the second group box into the form
cnbform.Controls.Add(gbox2)
//displays the checkboxes into the second groupbox
gbox2.Controls.Add(check1)
gbox2.Controls.Add(check2)

//inserts the exit button into the form
cnbform.Controls.Add(exitbutton)
//attach a click event to the first radio button then assign a function to it
radio1.Click.Add(fun r1msg->
//check the first checkbox
check1.Checked<-true
               //unchecks the first checkbox
                check2.Checked<-false)

//attach a click event to the first radio button then assign a function to it

radio2.Click.Add(fun r2msg->
//check the second checkbox
check2.Checked<-true
              //unchecks the first checkbox
              check1.Checked<-false)
//quits the form when the exit button is clicked                 
exitbutton.Click.Add(fun bact->cnbform.Close())    
//shows the form       
cnbform.Show()
//runs the application
Application.Run(cnbform)

5. Lets view of our again once again and this time, comments omitted:

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1. // Learn more about F# at http://fsharp.net  
2. open System  
3. open System.Drawing  
4. open System.Windows.Forms  
5. let cnbform=new Form(Text="Use Radio Button",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)  
6.   
7. let gbox1=new GroupBox(Text="RadioButtons", Location=new System.Drawing.Point(10,5),Height=80)  
8. let radio1=new RadioButton(Text="First radio button", Location=new System.Drawing.Point(20,20),AutoSize=true)  
9. let radio2=new RadioButton(Text="Second radio button", Location=new System.Drawing.Point(20,40),AutoSize=true)  
10.   
11. let gbox2=new GroupBox(Text="CheckBoxes",Height=80, Location=new System.Drawing.Point(10,100))  
12. let check1=new CheckBox(Text="First checkbox", Location=new System.Drawing.Point(20,20),AutoSize=true)  
13. let check2=new CheckBox(Text="Second checkbox", Location=new System.Drawing.Point(20,40),AutoSize=true)  
14.   
15. let exitbutton=new Button(Location=new System.Drawing.Point(200,200),Text="Exit")  
16.   
17.   
18. cnbform.Controls.Add(gbox1)  
19. gbox1.Controls.Add(radio1)  
20. gbox1.Controls.Add(radio2)  
21.   
22. cnbform.Controls.Add(gbox2)  
23. gbox2.Controls.Add(check1)  
24. gbox2.Controls.Add(check2)  
25.   
26. cnbform.Controls.Add(exitbutton)  
27.   
28. radio1.Click.Add(fun r1msg->  
29. check1.Checked<-true  
30.                     check2.Checked<-false)  
31. radio2.Click.Add(fun r2msg->  
32. check2.Checked<-true  
33.                     check1.Checked<-false)  
34.                       
35. exitbutton.Click.Add(fun bact->cnbform.Close())             
36. cnbform.Show()  
37. Application.Run(cnbform)  

// Learn more about F# at http://fsharp.net
open System
open System.Drawing
open System.Windows.Forms
let cnbform=new Form(Text="Use Radio Button",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)

let gbox1=new GroupBox(Text="RadioButtons", Location=new System.Drawing.Point(10,5),Height=80)
let radio1=new RadioButton(Text="First radio button", Location=new System.Drawing.Point(20,20),AutoSize=true)
let radio2=new RadioButton(Text="Second radio button", Location=new System.Drawing.Point(20,40),AutoSize=true)

let gbox2=new GroupBox(Text="CheckBoxes",Height=80, Location=new System.Drawing.Point(10,100))
let check1=new CheckBox(Text="First checkbox", Location=new System.Drawing.Point(20,20),AutoSize=true)
let check2=new CheckBox(Text="Second checkbox", Location=new System.Drawing.Point(20,40),AutoSize=true)

let exitbutton=new Button(Location=new System.Drawing.Point(200,200),Text="Exit")


cnbform.Controls.Add(gbox1)
gbox1.Controls.Add(radio1)
gbox1.Controls.Add(radio2)

cnbform.Controls.Add(gbox2)
gbox2.Controls.Add(check1)
gbox2.Controls.Add(check2)

cnbform.Controls.Add(exitbutton)

radio1.Click.Add(fun r1msg->
check1.Checked<-true
                    check2.Checked<-false)
radio2.Click.Add(fun r2msg->
check2.Checked<-true
                    check1.Checked<-false)
                    
exitbutton.Click.Add(fun bact->cnbform.Close())           
cnbform.Show()
Application.Run(cnbform)

6. Click the run icon to execute your application. You should now see an output similar to the following screen shot: