Delete Selected Dynamic Checkboxes on Gridview ASP.NET

I have a gridview that contains data from a database. I have dynamically created checkboxes for each row. What I want is when I click the "delete selected" button, the checkboxes that are checked will be deleted. But the rows don't get deleted when I click the button. Here is the code for the button:

protected void btnDeleteSelectedServiceProvidersLocations_Click(object sender, EventArgs e)
    {
        int x = 102;
        string delete;
        foreach (GridViewRow grow in gvServiceProviders.Rows)
        {
            delete = Request.Form["gvServiceProviders$ct" + x + "$cbSelect"];
            if (delete != null || delete == "on" || delete == "y")
            {
                bll.ServiceProviderLocationID = grow.Cells[1].Text;
                bll.IsDeleted = "y";
                bll.ServiceProviderLocationDelete();
            }
            x++;
        }
        gvServiceProviders.DataSource = bll.GetServiceProviderLocations();
        gvServiceProviders.DataBind();
    }

The gridview is inside an update panel, if that helps. And I'm using a three-tier approach.

ASPX code:

<div ID="gridView">
     <asp:GridView ID="gvServiceProviders" runat="server">
            <Columns>
                  <asp:templatefield HeaderText="Select">
                       <itemtemplate>
                                <asp:CheckBox ID="cbSelect" runat="server"/>
                       </itemtemplate>
                  </asp:templatefield>
            </Columns>
     </asp:GridView>
 </div>