Only accept digits for textbox

Question

I found this code for making my textbox only accept numbers.

Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
    Dim allowedChars As String = "0123456789"
    If allowedChars.IndexOf(e.KeyChar) = -1 Then
        ' Invalid Character
        e.Handled = True
    End If
End Sub

But... the user can't delete the numbers using the backspace button. How do I do then?

score 9 · Answer 1 · edited Jun 02 '11 at 12:42

 Private Sub txtValue_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles                 txtValue.KeyPress
        'Dim allowedChars As String = "0123456789"
        'If allowedChars.IndexOf(e.KeyChar) = -1 Then
        '    ' Invalid Character
        '    e.Handled = True
        'End If
        'If (e.KeyChar = Microsoft.VisualBasic.Chr(8)) Then
        '    e.Handled = True
        'End If
        If Char.IsDigit(e.KeyChar) = False And Char.IsControl(e.KeyChar) = False Then
            e.Handled = True
        End If
    End Sub

score 7 · Accepted Answer · answered Jan 26 '11 at 04:37

7

You also need to handle pasted text (there may not be a keypress). The best way to do this is with a MaskedTextBox.

answered Jan 26 '11 at 04:37

Joel Coehoorn

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I see! But now I have a problem: I don't want PromtChars. I just want an empty area. I can't set to no PromtChars. I tried setting to to a blank space, but, essentially, a blank space is still a character.. – Saturn Jan 26 '11 at 04:43
Hey! I found the way to handle pasted too : Select textbox1 and go to Properties and then : set the ShortcutsEnabled to "False", Done :) [voldemort](http://stackoverflow.com/users/555690/voldemort) – Mousa Alfhaily Apr 25 '15 at 13:20

Mousa Alfhaily · Answer 3 · 2017-09-16T18:00:02.313

3

voldemort

i develop your first code to allow the user to delete too.

Here is the code :

Dim BACKSPACE As Boolean

Private Sub TextBox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
    If e.KeyCode = Keys.Back Then
        BACKSPACE = True
    Else
        BACKSPACE = False
    End If
End Sub

Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
    If BACKSPACE = False Then
        Dim allowedChars As String = "0123456789"
        If allowedChars.IndexOf(e.KeyChar) = -1 Then
            e.Handled = True
        End If
    End If
End Sub

I Hope My Code Was Useful To You :)

edited Sep 16 '17 at 18:00

answered Apr 06 '15 at 14:07

Mousa Alfhaily

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I forgot : – Mousa Alfhaily Apr 25 '15 at 07:34
Hey! I found the way to handle pasted too : Select textbox1 and go to Properties and then : set the ShortcutsEnabled to "False", Done :) [voldemort](http://stackoverflow.com/users/555690/voldemort) – Mousa Alfhaily Apr 25 '15 at 13:23

score 1 · Answer 4 · answered Dec 10 '13 at 22:04

1

When I have had the requirement of an input which only accepts numbers, I have typically used the NumericUpDown class. It handles limits and decimals too.

answered Dec 10 '13 at 22:04

djv

15,168
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score 1 · Answer 5 · edited Jan 26 '11 at 04:46

Use this code, it will help you

Public Function OnlyDigitsOnKeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs)

Try

    If System.Char.IsDigit(e.KeyChar) = False And e.KeyChar <> Microsoft.VisualBasic.Chr(8)        And e.KeyChar <> Microsoft.VisualBasic.Chr(46) Or (InStr(sender.text, ".") > 0 And  e.KeyChar = Microsoft.VisualBasic.Chr(46)) 
    Then
                e.Handled = True
    End If
        Catch ex As Exception
            Common.ErrorHandler(ex)
        End Try
End Function

score 0 · Answer 6 · answered Jun 10 '13 at 16:05

 Private Sub txtValue_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtValue.KeyPress
    Dim allowedChars As String = "."
    'If allowedChars.IndexOf(e.KeyChar) = -1 Then
    '    ' Invalid Character
    '    e.Handled = True
    'End If
    'If (e.KeyChar = Microsoft.VisualBasic.Chr(8)) Then
    '    e.Handled = True
    'End If
    If Char.IsDigit(e.KeyChar) = False And Char.IsControl(e.KeyChar) = False And allowedChars.IndexOf(e.KeyChar) = -1 Then
        e.Handled = True
    End If
End Sub

can you explain why this code solves the asker's problem? Also, why are you leaving commented-out lines in your solution? — Kate Gregory, Jun 10 '13 at 16:26

score 0 · Answer 7 · edited Dec 19 '14 at 07:03

0

Private Sub TMarksTextBox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TMarksTextBox.KeyPress
        If e.KeyChar < "0" OrElse e.KeyChar > "9" AndAlso e.KeyChar <> ControlChars.Back Then
            e.Handled = True
        End If
End Sub

edited Dec 19 '14 at 07:03

Harry

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answered Nov 03 '13 at 16:57

Phillip Olivier

1

score 0 · Answer 8 · answered Dec 10 '13 at 21:56

Here is some code that I wrote. It allows the user to delete, and the user can make the textbox blank if they desire. It handles when the user types a disallowed character, and it also handles when the user pastes text into the textbox. If the user pastes a string into the box that is a mix of valid and invalid characters, the valid characters will appear in the textbox, and the invalid characters will not.

It also has logic in place to ensure that the cursor behaves normally. (A problem with setting the text to a new value is that the cursor is moved back to the beginning. This code tracks the original position, and makes adjustments to account for any invalid characters that are removed.)

This code can be placed in the TextChaned event of any textbox. Be sure to change the name from TextBox1 to match your textbox.

    Private Sub TextBox1_TextChanged(sender As System.Object, e As System.EventArgs) Handles TextBox1.TextChanged
    Dim selStart As Integer = TextBox1.SelectionStart
    Dim selMoveLeft As Integer = 0
    Dim newStr As String = "" 'Build a new string by copying each valid character from the existing string. The new string starts as blank and valid characters are added 1 at a time.

    For i As Integer = 0 To TextBox1.Text.Length - 1

        If "0123456789".IndexOf(TextBox1.Text(i)) <> -1 Then 'Characters that are in the allowed set will be added to the new string.
            newStr = newStr & TextBox1.Text(i)

        ElseIf i < selStart Then 'Characters that are not valid are removed - if these characters are before the cursor, we need to move the cursor left to account for their removal.
            selMoveLeft = selMoveLeft + 1

        End If
    Next

    TextBox1.Text = newStr 'Place the new text into the textbox.
    TextBox1.SelectionStart = selStart - selMoveLeft 'Move the cursor to the appropriate location.
End Sub

Note - if you have to do this for a bunch of textboxes, you can make a general purpose version of this by creating a sub that accepts a reference to a textbox as a parameter. Then you only need to call the sub from the TextChanged event.

Only accept digits for textbox

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