Public Class Form1
 
    Dim text1 As String
    Dim strIn As String
 
    Function CleanInput(ByVal strIn As String) As String
        ' Replace invalid characters with empty strings.
        Return System.Text.RegularExpressions.Regex.Replace(strIn, "[^\w\.@-]", _
          "")
    End Function
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) _
    Handles Button1.Click
 
        strIn = TextBox1.Text
        TextBox2.Text = CleanInput(strIn)
    End Sub
End Class