Keystrokes in WPF using F#

This article is a explanation about Keystroke in F#. When we make windows form application, it provides alternates for trapping the input of the Keyboard and Mouse. In this article you can see almost any individual keystroke. Mostly you trap the standard events like KeyUp, KeyDown, KeyPress for handling Keystrokes. Steps are given below.

You will display the Header Text For the events to show what things are going on. Below code show the HeaderText.

      // Display header text.
      let headTxt = new TextBlock();
      headTxt.FontWeight <- FontWeights.Bold;
      headTxt.Text <- headString;
      grd.Children.Add(headTxt) |>ignore

Step 1: Firstly Open a new project in F# using Visual Studio 2010. Select F# WPF Application template and give name to the Project, as shown in Below Image.

Step 2: Now add the below define refrences to your project by right clicking on project in Solution Explorer.

• PresentationCore

• PresentationFramework

• System

• System.Xaml

• UIAutomationTypes

• WindowsBase

Step 3: When you add all these references your solution explorer will look like below.

Step 4: Then Click on Program.fs file in solution Explorer and write below code in Program.fs window. Your Window will look like below.

#light
 
open System
open System.Windows
open System.Windows.Controls
open System.Windows.Documents
open System.Windows.Input
open System.Windows.Media 
open System.Windows.Shapes
 
let headString = "Key For Event   System-Key    Text      " +        "Ctrl-Text    System-Text    Ime      State of Key      " +
                    "  IsDown    IsUp       IsToggled     IsRepeat "
let frmtKyStrg = "{0,-10}         {1,-20}      {2,-10}    " +        "{3,-10}      {4,-15}        {5,-8}   {6,-7}    {7,-10}       {8,-10}    "
let frmtTxtStrg =   "  {0,-10}                              " +
                    "        {1,-10}         {2,-10}         {3,-10}"
                   
                   
type ExmnKyStrk  = class
   inherit Window
 
   val stck : StackPanel
   val scrl : ScrollViewer
 
   new () as this = {
        stck = new StackPanel()
        scrl = new ScrollViewer() } then
      this.Title <- "Key Strokes in WPF using F#"
      this.FontFamily <- new FontFamily("Vardana")
     
      let grd = new Grid()
      this.Content <- grd
    
      let rwdf = new RowDefinition()
      rwdf.Height <- GridLength.Auto;
      grd.RowDefinitions.Add(rwdf)
      grd.RowDefinitions.Add(new RowDefinition())
      // Display header text.
      let headTxt = new TextBlock();
      headTxt.FontWeight <- FontWeights.Bold;
      headTxt.Text <- headString;
      grd.Children.Add(headTxt) |>ignore
 
      grd.Children.Add(this.scrl) |>ignore
      Grid.SetRow(this.scrl, 1)
     
      this.scrl.Content <- this.stck
     
   override this.OnKeyDown (args:KeyEventArgs ) =
      base.OnKeyDown(args)
      this.DisplayKeyInfo(args)
 
   override this.OnKeyUp (args:KeyEventArgs ) =
      base.OnKeyUp(args)
      this.DisplayKeyInfo(args)
 
   override this.OnTextInput (args:TextCompositionEventArgs  ) =
      base.OnTextInput(args)
 
      let result = [| args.RoutedEvent.Name; args.Text;
                      args.ControlText; args.SystemText |]
     
      let strg = String.Format(frmtTxtStrg, (Array.map box result))
         
      this.DisplayInfo(strg);
 
   member this.DisplayKeyInfo (args:KeyEventArgs) =
  
      let tst = args.RoutedEvent.Name
      let result = [| args.RoutedEvent.Name; args.Key.ToString();
                     args.SystemKey.ToString(); args.ImeProcessedKey.ToString();
                     args.KeyStates.ToString(); args.IsDown.ToString();
                     args.IsUp.ToString(); args.IsToggled.ToString();
                     args.IsRepeat.ToString() |]
      let str =  String.Format(frmtKyStrg, (Array.map box result))
      this.DisplayInfo(str)
           
   member this.DisplayInfo (str:string) =
      let text = new TextBlock();
      text.Text <- str;
      this.stck.Children.Add(text) |>ignore
      this.scrl.ScrollToBottom();
end
 
#if COMPILED
[<STAThread()>]
do
    let aplctn =  Application() in
    aplctn.Run(new ExmnKyStrk()) |> ignore
#endif

Step 5: Now press F5 to execute the code.

Output

Summary

In this article I have discussed that how to implement Keystroke Event in WPF using F#.