How to total count Item in this way

i have data list my aspx page

<asp:DataList ID="dldetp" runat="server" Width="100%" 
                        onitemcommand="dldetp_ItemCommand">
    <ItemTemplate>
       <asp:HiddenField ID="hid1" runat="server" Value='<%#Eval("P_Id") %>' />
           <div class="details-left">
		<div class="details-left-slider">
		<ul id="etalage">
		  <li>
		    <a href="#">
                      <asp:Image ID="img1" runat="server" class="etalage_thumb_image" src='<%# "./Admin/P_T1Image/"+Eval("P_T1Image") %>' />
		      <img class="etalage_source_image" src='<%# "./Admin/P_L1Image/"+Eval("P_L1LargeImage") %>' />
		    </a>
		  </li>
		  <li>
		      <img class="etalage_thumb_image" src='<%# "./Admin/P_T2Image/"+Eval("P_T2Image") %>' />
		      <img class="etalage_source_image" src='<%# "./Admin/P_L2Image/"+Eval("P_L2LargeImage") %>' />
		  </li>
		</ul>
		</div>
		<div class="details-left-info">
		  <div class="details-right-head">
		    <h1><asp:Label ID="pname" runat="server" Text='<%#Eval("P_Name") %>'></asp:Label></h1>
		      <ul class="pro-rate">
			<li><a class="product-rate" href="#"> <label> </label></a> <span> </span></li>
			<li><a href="#">0 Review(s) Add Review</a></li>
		      </ul>
			<p class="product-detail-info"><%#Eval("P_Desc")%>. </p>
			<a class="learn-more" href="#"><h3>MORE DETAILS</h3></a>
			<div class="product-more-details">
			  <ul class="price-avl">
			    <li class="price"><span>INR<%#Eval("P_MPrice")%></span><label>INR <asp:Label ID="lblprice" runat="server" Text='<%#Eval("P_Price") %>'></asp:Label></label></li>
			    <li class="stock"><i>In stock</i></li>
			    <div class="clear"> </div>
			  </ul>
		          <asp:Button ID="btnModalPopup" runat="server"  CommandName="AddCart" Text="Add Cart" Style="background-color: Maroon;  color: White;"  />					
			</div>
                  </div>
		</div>
		<div class="clear"> </div>
	      </div>
    </ItemTemplate>
</asp:DataList>

and my cs code...........

protected void dldetp_ItemCommand(object source, DataListCommandEventArgs e)
  {    
    if (e.CommandName == "AddCart")
      {
        if (Session["EMail"] == null)
          {
            Response.Redirect("login.aspx");
          }
        else
          {            
            bal.Action = "SelectProductshow";
            bal.P_Id = Convert.ToInt32(Request.QueryString["id"]);
            DataTable dt = new DataTable();
            dt = bal.BalBind();
            if (dt.Rows.Count > 0)
              {
                bal.Action = "insertcat"