いくつかの方法で TextBox に 1 文字のみを許可する汎用スニペットをコーディングしました。コードはかなりうまく機能しますが、コード サイズが非常に大きいため、コードを簡略化できる場合は提案や変更を知りたいです。
#Region " [TextBox] Allow only 1 Character "
' By Elektro H@cker
' TextBox [Enter]
Private Sub TextBox_Enter(sender As Object, e As EventArgs) ' Handles TextBox1.MouseEnter
' Allign the character in the TextBox space
' If Not TextBox_Separator.TextAlign = HorizontalAlignment.Center Then TextBox_Separator.TextAlign = HorizontalAlignment.Center Then
' Disable Copy/Paste contextmenu by creating a new one
If sender.ContextMenuStrip Is Nothing Then sender.ContextMenuStrip = New ContextMenuStrip
End Sub
' TextBox [KeyPress]
Private Sub TextBox_KeyPress(sender As Object, e As KeyPressEventArgs) ' Handles TextBox1.KeyPress
Select Case sender.TextLength
Case 0 ' TextLength = 0
Select Case e.KeyChar
Case Chr(22) ' CTRL+V is pressed
' If Clipboard contains 0 or 1 character then paste the character.
e.Handled = IIf(Clipboard.GetText.Length <= 1, False, True)
Case Else ' Other key is pressed
e.Handled = False ' Print the character.
End Select ' e.KeyChar when TextLength = 0
Case 1 ' TextLength = 1
Select Case e.KeyChar
Case Convert.ToChar(Keys.Back) ' Backspace is pressed
e.Handled = False ' Delete the character
Case Chr(22) ' CTRL+V is pressed
Select Case sender.SelectionLength
Case 1 ' If 1 character is selected
' If Clipboard contains 0 or 1 character then paste the character.
e.Handled = IIf(Clipboard.GetText.Length <= 1, False, True)
Case Else ' If any text is selected
e.Handled = True ' Don't paste the characters.
End Select
Case Else ' Other key is pressed
' If any text is selected then don't print the character.
e.Handled = IIf(sender.SelectionLength = 1, False, True)
End Select ' e.KeyChar when TextLength = 1
End Select ' TextLength
End Sub
#End Region