'------------------------------------------------------------------------

'                             T R A P P I N G   K E Y S T R O K E S
'                               For Data Input and Functionality
'                                            Ron Kessler

'------------------------------------------------------------------------

'Updated 8/2/06 for C# 2005

'This app shows you how to trap any keystroke and make it do what you want! 
'It also shows how to validate user input by using the Keypress event of a textbox

'If you want, you can also make the ENTER key work like the TAB key. Look at the 
'KeyDown event for the form.

Option Explicit On

Public Class frmMain

    Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        '---add them up
        If Trim(txtFirst.TabIndex) = "" Or Trim(txtSecond.Text) = "" Then

            MsgBox("Please enter a number")

        Else
            Try
                Dim firstNumber As Single
                Dim secondNumber As Single

                firstNumber = Trim(txtFirst.Text)
                secondNumber = Trim(txtSecond.Text)

                lblAnswer.Text = firstNumber + secondNumber

            Catch

                MessageBox.Show("An error occured while adding the numbers", "System Message", MessageBoxButtons.OK, MessageBoxIcon.Error)
                txtFirst.Focus()
            End Try


        End If
    End Sub

    Private Sub txtFirst_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtFirst.KeyPress
        '---the KeyPress event only responds to "character keys" like numbers/letters
        '    It will not respond to F10 or # keys, for instance. For those use the KeyDown or KeyUp events
        Select Case e.KeyChar
            Case "0" To "9", "."
                e.Handled = False        'was error handled?  No because there is no error!
            Case ControlChars.Back
                e.Handled = False

                'Case "a" To "z"            'for alpha characters
                '    e.Handled = False
            Case Else
                e.Handled = True         'was NOT handled because there is an error so pass it to O/S to handle

        End Select
    End Sub

    Private Sub txtSecond_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtSecond.KeyPress
        '---the KeyPress event only responds to "character keys" like numbers/letters
        '    It will not respond to F10 or # keys, for instance. For those use the KeyDown or KeyUp events
        Select Case e.KeyChar
            Case "0" To "9", "."
                e.Handled = False        'was error handled?  No because there is no error!
            Case ControlChars.Back
                e.Handled = False

                'Case "a" To "z"            'for alpha characters
                '    e.Handled = False
            Case Else
                e.Handled = True         'was NOT handled because there is an error so pass it to O/S to handle

        End Select
    End Sub

    Private Sub frmMain_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyUp
        '---to trap the enter key and make it work like the tab key you must set KeyPreview = True on the form properties

        If e.KeyCode = Keys.Enter Then
            e.Handled = True
            Me.ProcessTabKey(True)
        End If
    End Sub

    Private Sub btnEnd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnd.Click
        Me.Close()
    End Sub

  
End Class