i have the following code:
Private Sub TxtPStof_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TxtPStof.KeyPress
e.Handled = Not (Char.IsDigit(e.KeyChar) Or e.KeyChar = ".")
End Sub
which allows only digits and . in my textbox, however i also need to be able to delete values using the backspace or the delete button.
Is this possible?
Thanks! :)
This is the wrong approach.
It’s universally agreed that restricting the user’s input is bad for the user experience, and you will invariably fail to handle special cases (what about Ctrl+V, for instance? Ah, you forgot about that. Everybody does).
Instead, .NET offers the Validating event for validating user input. You should intercept that event, not the keypress. Do allow users to enter text however they want; in particular, allow them to make mistakes (e.g. mistyping) without interruption – that would be extremely disruptive and not helpful.
Then, once they’re finished (because input focus leaves the control), do an input validation in one go.
While I totally agree with the answer from Konrad Rudolph
(It's really a messy affair to handle the user input in the KeyPress event)
I wish to give an answer at your question.
The MSDN in the KeyPress docs states that The KeyPress event is not raised by noncharacter keys. This means that you don't get the Delete key, but only the BackSpace key. You could handle this situation with this little change to your event handler
Private Sub TxtPStof_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TxtPStof.KeyPress
if e.KeyChar <> ControlChars.Back then
e.Handled = Not (Char.IsDigit(e.KeyChar) Or e.KeyChar = ".")
end if
End Sub
If Char.IsLetterOrDigit(e.KeyChar) Or e.KeyChar = ControlChars.Back Or e.KeyChar = "." Then
e.Handled = False
Else
e.Handled = True
End If
this code works fine for me.
If Not ((Asc(e.KeyChar) >= 48 And Asc(e.KeyChar) <= 57) Or Asc(e.KeyChar) = 46 Or Asc(e.KeyChar) = 8 Or Asc(e.KeyChar) = 127) Then
e.KeyChar = ""
e.Handled = False
End If
try this one:
If Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57 Then
If Not (Asc(e.KeyChar) = 8 Or Asc(e.KeyChar) = 46) Then e.Handled = True
End If
Private Sub textbox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles textbox.KeyPress
If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back Then
e.Handled = True
End If
End Sub
This should do what you want it to do.
Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
Dim NumString = "0123456789.-"
If Not NumString.Contains(e.KeyChar) Then
If Asc(e.KeyChar) <> 8 Then 'BackSpace is allowed
e.KeyChar = ""
End If
Else
If e.KeyChar = "-" Then
If Len(Trim(TxtDcrAmt.Text)) > 0 Then
e.KeyChar = ""
End If
End If
If e.KeyChar = "." Then
If TxtDcrAmt.Text.Contains(".") Then
e.KeyChar = ""
End If
End If
If TxtDcrAmt.Text.Contains(".") Then
Dim TLen As Integer = 0
TLen = TxtDcrAmt.Text.IndexOf(".") + 2
If Len(Trim(TxtDcrAmt.Text)) > TLen Then
e.KeyChar = ""
End If
End If
End If
End Sub
Put this on keypress event. This allows dots and numbers only
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) < 46 Or Asc(e.KeyChar) > 57 Or (Asc(e.KeyChar) < 48 And Asc(e.KeyChar) > 46) Then
e.Handled = True
End If
End If
Related
I would like to skip a part of validation and just make it so the text-box can't have anything I don't want in it.
The intention is to allow backspaces, spaces, and letters : d,r,i (upper and lower) be entered.
How can I make it so that no special characters get entered like {}, !, :;", etc.?
Private Sub txtParty_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtParty.KeyPress
'allows only numbers, letter, space, and backspace
If Char.IsControl(e.KeyChar) = False And Char.IsSeparator(e.KeyChar) = False And Char.IsLetterOrDigit(e.KeyChar) = True And e.KeyChar <> "d" And e.KeyChar <> "D" And e.KeyChar <> "r" And e.KeyChar <> "R" And e.KeyChar <> "i" And e.KeyChar <> "I" Then
e.Handled = True
End If
End Sub
Probably easier with a couple of If-Blocks to filter the data.
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs)
Handles TextBox1.KeyPress
If e.KeyChar <> ControlChars.Back AndAlso e.KeyChar <> " " Then
If Not Char.IsLetter(e.KeyChar) OrElse
Not "DRI".Contains(e.KeyChar.ToString.ToUpper) Then
e.Handled = True
End If
End If
End Sub
Of course, you would still have to intercept the Ctrl-V and remove the ContextMenuStrip to prevent pasting text into the TextBox.
I need to make the text box only accept Numbers Decimals and the Backspace. This is what I have so far and it works great for numbers and backspace but I have no idea what to do for periods. So any help would be great.
Private Sub txtlength_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtlength.KeyPress
If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back Then
e.Handled = True
End If
End Sub
e.Handled = Not (Char.IsDigit(e.KeyChar) Or e.KeyChar = ControlChars.Back Or e.KeyChar = ".")
I have a textbox and I am using the following to validate the user can only add numbers, but how can I let the user to write only one "."
Private Sub txtDiagnostic_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtConsultor.KeyPress
If e.KeyChar <> ChrW(Keys.Back) Then
If Char.IsNumber(e.KeyChar) Then
Else
e.Handled = True
End If
End If
End Sub
I was planing to use contains() or something but how can I realize the textbox has
only one dot? or how to allow the user can write a single dot and only one?
add this line before your first IF
If (e.KeyChar.ToString = ".") And (txtDiagnostic.Text.Contains(e.KeyChar.ToString)) Then
e.Handled = True
Exit Sub
End If
try this code good for money purposes
Private Sub LoanFeeTextBox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles LoanFeeTextBox.KeyPress
If Char.IsControl(e.KeyChar) Then
ElseIf Char.IsDigit(e.KeyChar) OrElse e.KeyChar = "."c Then
If LoanFeeTextBox.TextLength = 12 And LoanFeeTextBox.Text.Contains(".") = False Then
LoanFeeTextBox.AppendText(".")
ElseIf e.KeyChar = "." And LoanFeeTextBox.Text.IndexOf(".") <> -1 Then
e.Handled = True
ElseIf Char.IsDigit(e.KeyChar) Then
If LoanFeeTextBox.Text.IndexOf(".") <> -1 Then
If LoanFeeTextBox.Text.Length >= LoanFeeTextBox.Text.IndexOf(".") + 3 Then
e.Handled = True
End If
End If
End If
Else
e.Handled = True
End If
End Sub
How do I allow the space key and backspace key in VB.NET/ Visual Studio 2008?
Sample code:
Private Sub txtname_KeyPress(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.KeyPressEventArgs) _
Handles txtname.KeyPress
If e.KeyChar < "A" Or e.KeyChar > "z" And e.KeyChar <> ControlChars.Back Then
e.Handled = True
txtname.Clear()
Else
End If
End Sub
For Backspace use the Asc Function and test for the Hex Value, in this case 8, for the Space you can just test for " "
If Asc(e.KeyChar) = 8 OrElse e.KeyChar = " " OrElse e.KeyChar < "A" OrElse e.KeyChar > "z" Then
e.Handled = True
CType(sender, TextBox).Clear()
End If
If your question is how to check BackSpace and Space the above answer will work. To allow them along with your Text then do something like this
If Not ((Asc(e.KeyChar) = 8 OrElse e.KeyChar = " ") OrElse (e.KeyChar >= "A" AndAlso e.KeyChar <= "z")) Then
e.Handled = True
CType(sender, TextBox).Clear()
End If
Work at Visual Studio 2012:
Private Sub Username_KeyPress(sender As Object, e As KeyPressEventArgs) Handles Username.KeyPress
If Not (Char.IsNumber(e.KeyChar) Or Asc(e.KeyChar) = 8 Or Asc(e.KeyChar) = 32) Then
e.Handled = True
End If
End Sub
I'm creating a simple application in Vb.net where I need to perform certain validations. So I want a name textbox to accept only characters from a-z and A-Z for example.
For this I wrote the following code:
Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If Asc(e.KeyChar) <> 8 Then
If Asc(e.KeyChar) > 65 Or Asc(e.KeyChar) < 90 Or Asc(e.KeyChar) > 96 Or Asc(e.KeyChar) < 122 Then
e.Handled = True
End If
End If
End Sub
But somehow it is not allowing me to enter characters. When I try to enter any character it does nothing.
What causes this problem and how can I resolve it?
Alternatively, you can do something like this,
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) _
Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
Dim allowedChars As String = "abcdefghijklmnopqrstuvwxyz"
If Not allowedChars.Contains(e.KeyChar.ToString.ToLower) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
or if you still want the ASCII way, try this,
Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtName.KeyPress
If Not (Asc(e.KeyChar) = 8) Then
If Not ((Asc(e.KeyChar) >= 97 And Asc(e.KeyChar) <= 122) Or (Asc(e.KeyChar) >= 65 And Asc(e.KeyChar) <= 90)) Then
e.KeyChar = ChrW(0)
e.Handled = True
End If
End If
End Sub
both will behave the same.
This is a more abstract approach, but still effective nonetheless. It's straightforward and can just be added to the TextChanged event. You can use it with multiple textboxes by adding their handles to the sub and using a DirectCast().
Dim allowed As String = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
For Each c As Char In TextBox.Text
If allowed.Contains(c) = False Then
TextBox.Text = TextBox.Text.Remove(TextBox.SelectionStart - 1, 1)
TextBox.Select(TextBox.Text.Count, 0)
End If
Next
Summary: If an invalid character is entered, it will immediately be deleted (most of the time the character won't be visible long enough for the user to notice).
Private Sub txtname_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox5.KeyPress
If AscW(e.KeyChar) > 64 And AscW(e.KeyChar) < 91 Or AscW(e.KeyChar) > 96 And AscW(e.KeyChar) < 123 Or AscW(e.KeyChar) = 8 Then
Else
e.KeyChar = Nothing
End If
End Sub
I hope this helps!
Am using below code to accept only letters, "-" or "'" when user is entering a person name (maybe it is simple and easier):
Private Sub txtEName1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles txtEName1.KeyPress
If Char.IsLetter(e.KeyChar) Or e.KeyChar = vbBack Or e.KeyChar = "-" Or e.KeyChar = "'" Then
e.Handled = False
Else
e.Handled = True
End If
End Sub
I allowed the backspace in order to allow the user to remove letters in case of mistakes
Private Sub txtStudentName_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtStudentName.KeyPress
If Not Char.IsLetter(e.KeyChar) And Not e.KeyChar = Chr(Keys.Delete) And Not e.KeyChar = Chr(Keys.Back) And Not e.KeyChar = Chr(Keys.Space) Then
e.Handled = True
End If
End Sub