I have a simple user control with this code:

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="Pager.ascx.cs" Inherits="Pager" %>
<table style="width: 100%;">
    <tr>
        <td runat="server" id="PageControls">
            <!-- This button has the problem: -->
            <asp:Button ID="btnPrevPage" runat="server" Text="&larr;" OnClick="btnPrevPage_Click" />
            Page
            <asp:DropDownList runat="server" ID="ddlPage" AutoPostBack="true" OnSelectedIndexChanged="ddlPage_SelectedIndexChanged" />
            of
            <asp:Label ID="lblTotalPages" runat="server" />
            <!-- This button has the problem: -->
            <asp:Button ID="btnNextPage" runat="server" Text="&rarr;" OnClick="btnNextPage_Click" />
        </td>
        <td align="right" runat="server" id="itemsPerPageControls">
            <asp:Literal ID="perPageText1" runat="server" />
            <asp:DropDownList ID="ddlItemsPerPage" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlItemsPerPage_SelectedIndexChanged" />
            <asp:Literal ID="perPageText2" runat="server" />
        </td>
    </tr>
</table>

As you can see, the 2 buttons are wired to click events, which are defined correctly in the code-behind.

Now, here is how I include an instance of the control on my page:

 <uc:Pager ID="Pager1" runat="server" TotalRecords="100" DisplayItemsPerPage="true"
        ItemsPerPageChoices="10,25,50,100" ItemsPerPageFormatString="Sessions/Page: {0}"
        PageSize="25" OnPageChanged="PageChanged" OnPageSizeChanged="PageChanged" />

I noticed though, that the 2 buttons in my user control weren't causing a post back when clicked. The drop down list does cause postback, though. Here is the rendered HTML:

<table style="width: 100%;">
    <tr>
        <td id="ctl00_MainContent_Pager1_PageControls" align="left">
            <!-- No onclick event! Why? -->
            <input type="submit" name="ctl00$MainContent$Pager1$btnPrevPage" value="?" id="ctl00_MainContent_Pager1_btnPrevPage" />
            Page
            <select name="ctl00$MainContent$Pager1$ddlPage" onchange="javascript:setTimeout('__doPostBack(\'ctl00$MainContent$Pager1$ddlPage\',\'\')', 0)"
                id="ctl00_MainContent_Pager1_ddlPage">
                <option value="1">1</option>
                <option selected="selected" value="2">2</option>
                <option value="3">3</option>
                <option value="4">4</option>
                <option value="5">5</option>
                <option value="6">6</option>
            </select>
            of <span id="ctl00_MainContent_Pager1_lblTotalPages">6</span>
            <!-- No onclick event! Why? -->
            <input type="submit" name="ctl00$MainContent$Pager1$btnNextPage" value="?" id="ctl00_MainContent_Pager1_btnNextPage" />
        </td>
        <td id="ctl00_MainContent_Pager1_itemsPerPageControls" align="right">
            Sessions/Page:
            <select name="ctl00$MainContent$Pager1$ddlItemsPerPage" onchange="javascript:setTimeout('__doPostBack(\'ctl00$MainContent$Pager1$ddlItemsPerPage\',\'\')', 0)"
                id="ctl00_MainContent_Pager1_ddlItemsPerPage">
                <option value="10">10</option>
                <option selected="selected" value="25">25</option>
                <option value="50">50</option>
                <option value="100">100</option>
            </select>
        </td>
    </tr>
</table>

And, as you can see, there is no onclick attribute being rendered in the button's input elements. Why not?