TextBox Keyevent hander : TextBox : GUI Windows Forms C# Examples

    
using  System;
using  System.Drawing;
using  System.Collections;
using  System.ComponentModel;
using  System.Windows.Forms;
using  System.Data;

public  class  TextCancelEventKeyEvent  :  System.Windows.Forms.Form
{
    private  System.Windows.Forms.Label  label1;
    private  System.Windows.Forms.TextBox  txtInput;
    private  System.Windows.Forms.Label  label2;
    private  System.Windows.Forms.Label  lblTrue;
    private  System.Windows.Forms.Label  label3;
    private  System.Windows.Forms.Label  lblCheck;
        private  System.Windows.Forms.Label  lblResults;

    public  TextCancelEventKeyEvent()
    {
        InitializeComponent();
    }

    private  void  InitializeComponent()
    {
          this.label1  =  new  System.Windows.Forms.Label();
          this.txtInput  =  new  System.Windows.Forms.TextBox();
          this.label2  =  new  System.Windows.Forms.Label();
          this.lblTrue  =  new  System.Windows.Forms.Label();
          this.label3  =  new  System.Windows.Forms.Label();
          this.lblCheck  =  new  System.Windows.Forms.Label();
          this.lblResults  =  new  System.Windows.Forms.Label();
          this.SuspendLayout();
          //  
          //  label1
          //  
          this.label1.Font  =  new  System.Drawing.Font("Tahoma",  14.25F,  (System.Drawing.FontStyle.Bold  |  System.Drawing.FontStyle.Italic),  System.Drawing.GraphicsUnit.Point,  ((System.Byte)(0)));
          this.label1.Location  =  new  System.Drawing.Point(48,  16);
          this.label1.Name  =  "label1";
          this.label1.Size  =  new  System.Drawing.Size(176,  23);
          this.label1.TabIndex  =  0;
          this.label1.Text  =  "ISBN  Validation";
          //  
          //  txtInput
          //  
          this.txtInput.Location  =  new  System.Drawing.Point(72,  64);
          this.txtInput.Name  =  "txtInput";
          this.txtInput.TabIndex  =  1;
          this.txtInput.Text  =  "";
          this.txtInput.KeyPress  +=  new  System.Windows.Forms.KeyPressEventHandler(this.txtInput_KeyPress);
          this.txtInput.Validating  +=  new  System.ComponentModel.CancelEventHandler(this.handleCancleEvent);
          //  
          //  label2
          //  
          this.label2.Location  =  new  System.Drawing.Point(24,  104);
          this.label2.Name  =  "label2";
          this.label2.Size  =  new  System.Drawing.Size(80,  23);
          this.label2.TabIndex  =  2;
          this.label2.Text  =  "True  Number:";
          //  
          //  lblTrue
          //  
          this.lblTrue.BorderStyle  =  System.Windows.Forms.BorderStyle.Fixed3D;
          this.lblTrue.Location  =  new  System.Drawing.Point(112,  104);
          this.lblTrue.Name  =  "lblTrue";
          this.lblTrue.TabIndex  =  3;
          //  
          //  label3
          //  
          this.label3.Location  =  new  System.Drawing.Point(32,  152);
          this.label3.Name  =  "label3";
          this.label3.Size  =  new  System.Drawing.Size(72,  23);
          this.label3.TabIndex  =  4;
          this.label3.Text  =  "Check  Digit:";
          //  
          //  lblCheck
          //  
          this.lblCheck.BorderStyle  =  System.Windows.Forms.BorderStyle.Fixed3D;
          this.lblCheck.Location  =  new  System.Drawing.Point(112,  152);
          this.lblCheck.Name  =  "lblCheck";
          this.lblCheck.TabIndex  =  5;
          //  
          //  lblResults
          //  
          this.lblResults.Location  =  new  System.Drawing.Point(56,  192);
          this.lblResults.Name  =  "lblResults";
          this.lblResults.Size  =  new  System.Drawing.Size(152,  24);
          this.lblResults.TabIndex  =  8;
          //  
          //  TextCancelEventKeyEvent
          //  
          this.AutoScaleBaseSize  =  new  System.Drawing.Size(5,  13);
          this.ClientSize  =  new  System.Drawing.Size(264,  293);
          this.Controls.AddRange(new  System.Windows.Forms.Control[]  {
                                                                                                                                    this.lblResults,
                                                                                                                                    this.lblCheck,
                                                                                                                                    this.label3,
                                                                                                                                    this.lblTrue,
                                                                                                                                    this.label2,
                                                                                                                                    this.txtInput,
                                                                                                                                    this.label1});
          this.ResumeLayout(false);

    }
    [STAThread]
    static  void  Main()  
    {
        Application.Run(new  TextCancelEventKeyEvent());
    }

    private  void  handleCancleEvent(object  sender,  System.ComponentModel.CancelEventArgs  e)
    {
        TextBox  tb  =  (TextBox)sender;
        string  strInput  =  tb.Text;
                Console.WriteLine(strInput);
    }          

    private  void  txtInput_KeyPress(object  sender,  System.Windows.Forms.KeyPressEventArgs  e)
    {
          char  keyChar;
          keyChar  =  e.KeyChar;

          if(!Char.IsDigit(keyChar)            //  0  -  9
                &&
                keyChar  !=  8                              //  backspace
                &&
                keyChar  !=  13                            //  enter
                &&
                keyChar  !=  'x'
                &&
                keyChar  !=  45                            //    dash/minus
                ){
                //    Do  not  display  the  keystroke
                e.Handled  =  true;
          }
    }          
}