C# と VB.NET の質問掲示板

■No93933 (yuji さん) に返信
> フォームに用意したテキストボックスへの入力値を
> 16進数の0〜9とa〜fのみ入力できるようにしたいのですが
> 方法がわからないのでご教授願います。

こんな感じでカスタムコントロールを作っては？

Public Class HexadecimalTextBox
    Inherits TextBox

    Private Const WM_PASTE As Integer = &H302

    Private Shared CTRL_BASE As Integer = AscW("A"c) - 1
    Private Shared CTRL_A As Char = ChrW(AscW("A"c) - CTRL_BASE)
    Private Shared CTRL_C As Char = ChrW(AscW("C"c) - CTRL_BASE)
    Private Shared CTRL_V As Char = ChrW(AscW("V"c) - CTRL_BASE)
    Private Shared CTRL_X As Char = ChrW(AscW("X"c) - CTRL_BASE)
    Private Shared CTRL_Z As Char = ChrW(AscW("Z"c) - CTRL_BASE)

    Protected Overrides Sub OnKeyPress(e As KeyPressEventArgs)
        Select Case e.KeyChar
            Case CTRL_A
                Me.SelectAll()
                e.Handled = True
            Case CTRL_C, CTRL_V, CTRL_X, CTRL_Z
            Case ControlChars.Back
            Case Else
                e.KeyChar = RestrictChar(e.KeyChar)
                e.Handled = (e.KeyChar = ChrW(0))
        End Select
        MyBase.OnKeyPress(e)
    End Sub

    Protected Overridable Function RestrictChar(c As Char) As Char
        Select Case c
            Case "0"c To "9"c, "a"c To "f"c
                Return c
            Case "A"c To "F"c
                Return Char.ToLower(c)
            Case Else
                Return ChrW(0)
        End Select
    End Function

    Protected Overrides Sub WndProc(ByRef m As Message)
        Select Case m.Msg
            Case WM_PASTE
                If Clipboard.ContainsText() Then
                    Dim sb As New Text.StringBuilder()
                    Dim pasteMaxLength As Integer
                    If MaxLength > 0 Then
                        pasteMaxLength = MaxLength - TextLength + SelectionLength
                    Else
                        pasteMaxLength = Integer.MaxValue - TextLength + SelectionLength
                    End If
                    For Each c As Char In Clipboard.GetText()
                        If sb.Length >= pasteMaxLength Then
                            Exit For
                        End If
                        Dim rc As Char = RestrictChar(c)
                        If rc <> ChrW(0) Then
                            sb.Append(rc)
                        End If
                    Next
                    MyBase.Paste(sb.ToString())
                End If
            Case Else
                MyBase.WndProc(m)
        End Select
    End Sub

End Class