I have a dropdownlist in my web page and two command buttons and a tabcontainer. The tabcontainer does not appear after the load of page according to my code.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not IsPostBack Then


        TabContainer1.Visible = False

        If CtvAct.GetRecords("Fill_RequestTypeTb") = True Then
            ReqTypeCmbo.DataSource = CtvAct.MainDataset.Tables("tbOLRequestType").DefaultView
            ReqTypeCmbo.DataTextField = "RequestTypeName"
            ReqTypeCmbo.DataValueField = "RequestTypeId"
            ReqTypeCmbo.DataBind()
            Dim itm As New ListItem
            itm.Text = "-- ??? ??? ????? --"
            itm.Value = "-1"
            itm.Selected = True
            ReqTypeCmbo.Items.Insert(0, itm)
            ReqTypeCmbo.SelectedIndex = 0
        End If
    End If
End Sub


Protected Sub PrntCmd_Click(ByVal sender As Object, ByVal e As EventArgs) Handles PrntCmd.Click
    TextBox6.Text = "gggg"
End Sub

If I press any button after page load the button work very selecting any item from dropdownlist make the tabcontainer appear but after the tabcontainer appear, the buttons does not work (postback) how can I solve these problems