C# asp.net 页面加载的过程是前台页面先加载还是后台的，求解

前台页面部分代码（关键是第一行代码 var item in list）
<%foreach (var item in list)
{ %>
<tr class="tdbg" align="center">
<td>
<input type="checkbox" name="sel" id="sel_<%=item.ID %>" value="ON" />
</td>
<td align="left" style="text-indent: 10px;">
、、、
后台代码
全局变量
protected localhost.V_Product[] list;
protected void Page_Load(object sender, EventArgs e) {
try {
if (!IsPostBack) {
if (Request["action"] == "check") {
UncheckBind();
}
if (Request["action"] == "signup") {
CheckedBind();
}
}

}
catch (Exception ex) {
Msg = MF.Com.ArtDialog.ShowSadTip(ex.Message);
}
}

private void CheckedBind() {
string where = "1=1";
int totalRecords;
list = service.GetPaged(where, " [CreateTime] Asc", anp.CurrentPageIndex - 1, anp.PageSize, out totalRecords);
anp.RecordCount = totalRecords;
}