Dim txtb() As TextBox = {txtA, txtB, txtC}
           For Each ctrl As TextBox In txtb
                ctrl.Text = "" 
           Next

For Each ctrl As Object In Me.Controls
                If ctrl.GetType.Name = "TextBox" Then
                    ' do something
                End If
          Next

 Public Sub ClearControl(ByVal root As Control)
        For Each ctrl As Control In root.Controls
            ClearControl(ctrl)
            If TypeOf ctrl Is TextBox Then
                CType(ctrl, TextBox).Text = String.Empty
            ElseIf TypeOf ctrl Is ComboBox Then
                CType(ctrl, ComboBox).Text = String.Empty
            End If
        Next ctrl
    End Sub
 
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
    ClearControl(Me)
End Sub