使用“蒙版”文本框分隔数字

Question

I don't know how to work with this, I have this who's input will be a valid sss or tin number (eg 111-1111-111)

Example Picture

and my code is:

Public Class Form1

    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
        If TextBox1.Text.Length = 4 Then
            TextBox1.Text &= "-"
            TextBox1.Select(TextBox1.Text.Length, 0)
        ElseIf TextBox1.Text.Length = 11 Then
            TextBox1.Text &= "-"
            TextBox1.Select(TextBox1.Text.Length, 0)
        End If
    End Sub
End Class

Answer 1

Use a MaskedTextBox and set the Mask() property to 0000-000000-000 . The dash will be inserted for you as the digits are typed.