Navigate ASP.Net Ajax Tabs Next Previous on Button Click Server Side

Seems like you are making mistake or not following replies. Anyways here's a working sample that works for me

  <asp:Button Text="Previous" runat="server" OnClick="PreviousTab" />
    <asp:Button Text="Next" runat="server" OnClick="NextTab" />
    <cc1:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0">
        <cc1:TabPanel ID="TabPanel1" runat="server" HeaderText="TabPanel1" ToolTip="Tooltip_TabPanel1">
            <ContentTemplate>
                Tab 1
            </ContentTemplate>
        </cc1:TabPanel>
        <cc1:TabPanel ID="TabPanel2" runat="server" HeaderText="TabPanel2" ToolTip="Tooltip_TabPanel2">
            <ContentTemplate>
                Tab 2
            </ContentTemplate>
        </cc1:TabPanel>
        <cc1:TabPanel ID="TabPanel3" runat="server" HeaderText="TabPanel3" ToolTip="Tooltip_TabPanel3">
            <ContentTemplate>
                Tab 3
            </ContentTemplate>
        </cc1:TabPanel>
    </cc1:TabContainer>

    protected void NextTab(object sender, EventArgs e)
    {
        TabContainer1.ActiveTabIndex++;
    }
    protected void PreviousTab(object sender, EventArgs e)
    {
        TabContainer1.ActiveTabIndex--;
    }