How can i control multiply textbox only allow write numeric and show "-" on beginning

Question

here is my code Private Sub textBox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles textBox1.KeyPress If Not (Char.IsDigit(e.KeyChar) OrElse e.KeyChar = "-" OrElse e.KeyChar = ChrW(Keys.Back) OrElse e.KeyChar = ChrW(Keys.Delete)) Then ' Ignore the keypress event e.Handled = True End If If e.KeyChar = "-" AndAlso (TryCast(sender, TextBox).Text <> "" AndAlso TryCast(sender, TextBox).SelectionStart <> 0) Then ' Ignore the keypress event e.Handled = True End If End Sub

Answer 1

Hi @Tian ,

Please try the following code to ensure that only one - is allowed at the beginning and - only allowed at the beginning.

Also allow Backspace and Delete keys.

Private Sub textBox_KeyPress(sender As Object, e As KeyPressEventArgs) Handles textBox1.KeyPress
    Dim textBox As TextBox = TryCast(sender, TextBox)

    ' Allow digits, "-", Backspace, and Delete
    If Not (Char.IsDigit(e.KeyChar) OrElse e.KeyChar = "-" OrElse e.KeyChar = ChrW(Keys.Back) OrElse e.KeyChar = ChrW(Keys.Delete)) Then
        e.Handled = True
    End If

    ' Allow "-" only at the beginning and prevent more than one "-"
    If e.KeyChar = "-" AndAlso (textBox.Text <> "" OrElse textBox.SelectionStart <> 0 OrElse textBox.Text.Contains("-")) Then
        e.Handled = True
    End If
End Sub

Best Regards.

Jiachen Li

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