Using a timer control in Visual F#

Timer controls are used to automatically execute an action after a specified time has elapsed. To create a timer control in F#, use the following syntax:

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1. let timerobjvariable=new Timer()  

let timerobjvariable=new Timer()

For instance:

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1. let timer=new Timer()  

let timer=new Timer()

For a simple example on using a timer control, 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 from the .Net tab.

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 F# library  
3. open System  
4. //use this to enable the intellisense. Very helpful in coding your application  
5. open System.Drawing   
6. //specify the location of the Form classes  
7. open System.Windows.Forms  
8. //creates a form  
9. let timerform=new Form(Text="Use Timer",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)  
10. //use the random function to generate random numbers  
11. let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 220))  
12. let random=new Random()  
13. //create a timer object and set its interval to 1 second  
14. //by default timer are disabled so you'll need to enable it  
15. let timer1=new Timer(Interval=1000,Enabled=true)  
16. //assigns a random backcolor to our form   
17. //change it every 1 second  
18. timer1.Tick.Add(fun time->timerform.BackColor<-Color.FromArgb(random.Next(0,255),random.Next(0,255),random.Next(0,255)))  
19. //adds the exit button to our form  
20. timerform.Controls.Add(exitbutton)  
21. //when the exit button is clicked  
22. exitbutton.Click.Add(fun quit->  
23. //stops the time  
24. timer1.Stop()  
25. //close the form  
26. timerform.Close())                     
27. //show our form  
28. timerform.Show()  
29. //execute our application  
30. Application.Run(timerform)  

// Learn more about F# at http://fsharp.net
//use the F# library
open System
//use this to enable the intellisense. Very helpful in coding your application
open System.Drawing 
//specify the location of the Form classes
open System.Windows.Forms
//creates a form
let timerform=new Form(Text="Use Timer",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font)
//use the random function to generate random numbers
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 220))
let random=new Random()
//create a timer object and set its interval to 1 second
//by default timer are disabled so you'll need to enable it
let timer1=new Timer(Interval=1000,Enabled=true)
//assigns a random backcolor to our form 
//change it every 1 second
timer1.Tick.Add(fun time->timerform.BackColor<-Color.FromArgb(random.Next(0,255),random.Next(0,255),random.Next(0,255)))
//adds the exit button to our form
timerform.Controls.Add(exitbutton)
//when the exit button is clicked
exitbutton.Click.Add(fun quit->
//stops the time
timer1.Stop()
//close the form
timerform.Close())                   
//show our form
timerform.Show()
//execute our application
Application.Run(timerform)

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



If you want a more in depth explanation on this controls, visit the MSDN website at msdn.microsoft.com or the Microsoft F# Development Center at http://msdn.microsoft.com/en-us/fsharp/default.aspx

Activating a new Form at run-time (Visual F#)

To activate a new form at run-time, simply use the Show and Hide methods of the form. The following steps demonstrate a simple example:

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 from the .Net tab.

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

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1. //use the F# standard library  
2. open System  
3. //use the drawing class  
4. open System.Drawing   
5. //Specifies the memory location of the form class  
6. open System.Windows.Forms   
7. //create a font object  
8. let ffont=new Font("Arial",12.0f,FontStyle.Bold, GraphicsUnit.Point)  
9. //creates a form named “firstform”  
10. let firstform=new Form(Text="Display First Form",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)  
11. //creates a label,sets its caption to “This is the first form”  
12. let fformlabel=new Label(Text="This is the first form",AutoSize=true)  
13. //make a button,sets its caption to Second Form  
14. let nxtbutton=new Button(Text="Second Form", Location=new System.Drawing.Point(100, 200),AutoSize=true)  
15. //creates another button, set its text to exit  
16. let fexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200),AutoSize=true)  
17. //adds the controls we made to the first form  
18. firstform.Controls.Add(fformlabel)  
19. //applies font format to our label  
20. fformlabel.Font<-ffont  
21. firstform.Controls.Add(nxtbutton)  
22. firstform.Controls.Add(fexitbutton)  
23. //when the “Second Form” button of the first form is clicked  
24. nxtbutton.Click.Add(fun nxtform->  
25. //hides the first form  
26. firstform.Hide()  
27. //create a new form named secondform  
28. let secondform=new Form(Text="Second Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)  
29. //create a label and sets its caption to “This is the second form”  
30. let sformlabel=new Label(Text="This is the second form",AutoSize=true)  
31. //creates a button and sets its text to “First Form”  
32. let prevbutton=new Button(Text="First Form", Location=new System.Drawing.Point(100, 200))  
33. //adds a button, set its text to “Exit”  
34. let sexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))  
35. //show the second form  
36. secondform.Show()  
37. //add the controls we made on the second form  
38. secondform.Controls.Add(sformlabel)  
39. //applies font format to our label  
40. sformlabel.Font<-ffont  
41. secondform.Controls.Add(prevbutton)  
42. secondform.Controls.Add(sexitbutton)  
43. //when the “First Form” button of the second form is clicked  
44. prevbutton.Click.Add(fun prevform->  
45. //show the first form  
46. firstform.Show()  
47. //hide the second form  
48. secondform.Hide())  
49. //when the exit button of the second form is clicked  
50. sexitbutton.Click.Add(fun quit->  
51. //close the first form  
52. firstform.Close()  
53. //close the second form  
54. secondform.Close()))  
55. //when the exit button of the first form is clicked  
56. //close the first form  
57. fexitbutton.Click.Add(fun quit->firstform.Close())                       
58. firstform.Show()  
59. //executes our application  
60. Application.Run(firstform)  

//use the F# standard library
open System
//use the drawing class
open System.Drawing 
//Specifies the memory location of the form class
open System.Windows.Forms 
//create a font object
let ffont=new Font("Arial",12.0f,FontStyle.Bold, GraphicsUnit.Point)
//creates a form named “firstform”
let firstform=new Form(Text="Display First Form",StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)
//creates a label,sets its caption to “This is the first form”
let fformlabel=new Label(Text="This is the first form",AutoSize=true)
//make a button,sets its caption to Second Form
let nxtbutton=new Button(Text="Second Form", Location=new System.Drawing.Point(100, 200),AutoSize=true)
//creates another button, set its text to exit
let fexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200),AutoSize=true)
//adds the controls we made to the first form
firstform.Controls.Add(fformlabel)
//applies font format to our label
fformlabel.Font<-ffont
firstform.Controls.Add(nxtbutton)
firstform.Controls.Add(fexitbutton)
//when the “Second Form” button of the first form is clicked
nxtbutton.Click.Add(fun nxtform->
//hides the first form
firstform.Hide()
//create a new form named secondform
let secondform=new Form(Text="Second Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)
//create a label and sets its caption to “This is the second form”
let sformlabel=new Label(Text="This is the second form",AutoSize=true)
//creates a button and sets its text to “First Form”
let prevbutton=new Button(Text="First Form", Location=new System.Drawing.Point(100, 200))
//adds a button, set its text to “Exit”
let sexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
//show the second form
secondform.Show()
//add the controls we made on the second form
secondform.Controls.Add(sformlabel)
//applies font format to our label
sformlabel.Font<-ffont
secondform.Controls.Add(prevbutton)
secondform.Controls.Add(sexitbutton)
//when the “First Form” button of the second form is clicked
prevbutton.Click.Add(fun prevform->
//show the first form
firstform.Show()
//hide the second form
secondform.Hide())
//when the exit button of the second form is clicked
sexitbutton.Click.Add(fun quit->
//close the first form
firstform.Close()
//close the second form
secondform.Close()))
//when the exit button of the first form is clicked
//close the first form
fexitbutton.Click.Add(fun quit->firstform.Close())                     
firstform.Show()
//executes our application
Application.Run(firstform)

Here is our sample code again and this time comments omitted.

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1. open System  
2. open System.Drawing    
3. open System.Windows.Forms  
4. let ffont=new Font("Arial",12.0f,FontStyle.Bold, , GraphicsUnit.Point)   
5. let firstform=new Form(Text="First Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)  
6. let fformlabel=new Label(Text="This is the first form",AutoSize=true)  
7. let nxtbutton=new Button(Text="Second Form", Location=new System.Drawing.Point(100, 200),AutoSize=true)  
8. let fexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200),AutoSize=true)  
9. firstform.Controls.Add(fformlabel)  
10. fformlabel.Font<-ffont  
11. firstform.Controls.Add(nxtbutton)  
12. firstform.Controls.Add(fexitbutton)  
13.   
14. nxtbutton.Click.Add(fun nxtform->  
15. firstform.Hide()  
16. let secondform=new Form(Text="Second Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)  
17. let sformlabel=new Label(Text="This is the second form",AutoSize=true)  
18. let prevbutton=new Button(Text="First Form", Location=new System.Drawing.Point(100, 200))  
19. let sexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))  
20. secondform.Show()  
21. secondform.Controls.Add(sformlabel)  
22. sformlabel.Font<-ffont  
23. secondform.Controls.Add(prevbutton)  
24. secondform.Controls.Add(sexitbutton)  
25. prevbutton.Click.Add(fun prevform->  
26. firstform.Show()  
27. secondform.Hide())  
28. sexitbutton.Click.Add(fun quit->  
29. firstform.Close()  
30. secondform.Close()))    
31.   
32. fexitbutton.Click.Add(fun quit->firstform.Close())                       
33. firstform.Show()  
34. Application.Run(firstform)  

open System
open System.Drawing  
open System.Windows.Forms
let ffont=new Font("Arial",12.0f,FontStyle.Bold, , GraphicsUnit.Point) 
let firstform=new Form(Text="First Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)
let fformlabel=new Label(Text="This is the first form",AutoSize=true)
let nxtbutton=new Button(Text="Second Form", Location=new System.Drawing.Point(100, 200),AutoSize=true)
let fexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200),AutoSize=true)
firstform.Controls.Add(fformlabel)
fformlabel.Font<-ffont
firstform.Controls.Add(nxtbutton)
firstform.Controls.Add(fexitbutton)

nxtbutton.Click.Add(fun nxtform->
firstform.Hide()
let secondform=new Form(Text="Second Form", StartPosition=FormStartPosition.CenterScreen,AutoScaleMode=AutoScaleMode.Font,ClientSize=new System.Drawing.Size(200,200),FormBorderStyle=FormBorderStyle.FixedSingle)
let sformlabel=new Label(Text="This is the second form",AutoSize=true)
let prevbutton=new Button(Text="First Form", Location=new System.Drawing.Point(100, 200))
let sexitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
secondform.Show()
secondform.Controls.Add(sformlabel)
sformlabel.Font<-ffont
secondform.Controls.Add(prevbutton)
secondform.Controls.Add(sexitbutton)
prevbutton.Click.Add(fun prevform->
firstform.Show()
secondform.Hide())
sexitbutton.Click.Add(fun quit->
firstform.Close()
secondform.Close()))  

fexitbutton.Click.Add(fun quit->firstform.Close())                     
firstform.Show()
Application.Run(firstform)

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