ASP.Net AJAX TabContainer OnActiveTabChanged event example

Here I have created sample that will help you out.

HTML

<div>
    <ajax:ToolkitScriptManager runat="server">
    </ajax:ToolkitScriptManager>
    <ajax:TabContainer ID="TabContainer_PayrollHeadsTemplate" runat="server" ActiveTabIndex="0"
        AutoPostBack="true" Width="520px" OnActiveTabChanged="TabContainer_PayrollHeadsTemplate_ActiveTabChanged">
        <ajax:TabPanel ID="TabPanel1" runat="server" HeaderText="Name" TabIndex="545" DynamicContextKey="Name">
            <ContentTemplate>
                Enter Name :
                <asp:TextBox ID="txtName" runat="server" />
            </ContentTemplate>
        </ajax:TabPanel>
        <ajax:TabPanel ID="tp_MonthlyEarnings" runat="server" HeaderText="Monthly Earnings"
            TabIndex="545" DynamicContextKey="MonthlyEarnings">
            <ContentTemplate>
                <asp:CheckBoxList ID="cblMonthlyEarnings" runat="server">
                </asp:CheckBoxList>
            </ContentTemplate>
        </ajax:TabPanel>
    </ajax:TabContainer>
</div>

Code

protected void TabContainer_PayrollHeadsTemplate_ActiveTabChanged(object sender, EventArgs e)
{
    if (TabContainer_PayrollHeadsTemplate.ActiveTabIndex == 1)
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("EarningSlapId", typeof(int));
        dt.Columns.Add("EarningSlap", typeof(string));
        dt.Rows.Add(1, "8000 - 12000");
        dt.Rows.Add(1, "12000 - 15000");
        dt.Rows.Add(1, "15000 - 20000");
        cblMonthlyEarnings.DataSource = dt;
        cblMonthlyEarnings.DataTextField = "EarningSlap";
        cblMonthlyEarnings.DataValueField = "EarningSlapId";
        cblMonthlyEarnings.DataBind();
    }
}

Screenshot