Limit the # of digits after a decimal in a KeyPress Event Procedure

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  13 years ago

  by stevenyoo321

  steven yoo

  , United States

  Joined 13 years ago
  Greetings Everyone!
  I'm currently just starting to learn VB.net on my own. I have a simple question in what is the correct way to restrict the number of digits after the decimal point? As shown with my code below I was able to create a textbox in which when a user enters value such as 1232.23232 is possible...however I want to make the textbox more user friendly I restricting digits after the decimal to 2. So it would look more like this 1232.23. Thank you for all your time..any guidance and help would be greatly appreciated.
  
  Public Class Form1
  
  Private Sub txtPayment_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtPayment.KeyPress
  Const x As Integer = 2
  If e.KeyChar = Chr(8) Then Exit Sub
  
  Select Case e.KeyChar
  Case "0" To "9"
  'ok
  Case "."
  If (InStr(txtPayment.Text, ".")) <> x Then
  e.Handled = True
  Beep()
  End If
  Case Else
  e.Handled = True
  Beep()
  End Select
  
  
  End Sub
  End Class
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
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  13 years ago

  by tsalim

  Salim T

  , Qatar

  Joined 13 years ago

  hi friend,

  pls change the code of marked in red

   

  Public Class Form1
  
  Private Sub txtPayment_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtPayment.KeyPress
  Const x As Integer = 2
  If e.KeyChar = Chr(8) Then Exit Sub
  
  Select Case e.KeyChar
  Case "0" To "9"
  'ok
  Case "."
  If  Len(Mid(txtPayment.Text, InStr(txtPayment.Text, "."))) <> x Then
  e.Handled = True
  Beep()
  End If
  Case Else
  e.Handled = True
  Beep()
  End Select
  
  
  End Sub
  End Class
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

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  13 years ago

  by stevenyoo321

  steven yoo

  , United States

  Joined 13 years ago

  Greetings Tsalim! Thank you for your reply.

  However I tried replacing my code with your code in red. But it didn't work. Do you know of any problems there may be?

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  13 years ago

  by TwoFaced

  Thomas Reynard

  , United States

  Joined 15 years ago

  The case the red code is in, is for the "." being pressed.  For that case you should be limiting the user to a single ".".  What you should do there is test that a "." doesn't already exist in the textbox because a number can't have more then one ".".  You can do this easily using the contains method.  Something like

  If TextBox1.Text.Contains(".") then
  e.handled = true
  beep
  end if

  To limit the number of characters after the decimal is a little tricky. This is because a user editing the textbox isn't necessarily making a changes from left to right. They may go back to the 2nd position (which may be before the decimal) to enter a number they missed. One way to handle this would be to create the final string and then make sure you don't have to many digits after the decimal.  Try adding this code in case "0" to "9".

          Const MAX As Integer = 2
              'Create the Final string if we allow this character
              Dim temp As String = TextBox1.Text.Insert(TextBox1.SelectionStart, e.KeyChar)
              'Where is the "."
              Dim DecLoc As Integer = temp.IndexOf(".")
              If DecLoc >= 0 AndAlso temp.Length - DecLoc - 1 > MAX Then
                  'To many digits after the decimal place...Don't allow digit
                  e.Handled = True
                  Beep()
              End If
  

  You'll have to change a few variable names but that code should work for you.

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