if condition is not working in Datalist Itemcommand

protected void DataList1_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandName == "Cart")
        {
            Response.Redirect("Addtocart.aspx?ProductID=" + e.CommandArgument.ToString());
            da = new SqlDataAdapter("select count(*) from rsa_addtocart tatc inner join rsa_Users tl on tatc.UserId=tl.UserId where tatc.productid=" + Convert.ToInt32(e.CommandArgument.ToString()) + " and tl.UserId=" + Convert.ToInt32(Session["UserId"].ToString()) + " and tatc.UserId=" + Convert.ToInt32(Session["UserId"].ToString()) + " ", con);
            int n = Convert.ToInt32(da.SelectCommand.ExecuteScalar());
            if (n == 1)
            {
                da = new SqlDataAdapter("select tpd.ProductID,tpd.ProductName,tpd.Price,tpd.ProductImage,tl.UserId,tatc.cartId from rsa_ProductItemTable tpd inner join rsa_addtocart tatc on tpd.ProductID=tatc.productid inner join rsa_Users tl on tl.UserId=tatc.UserId where tatc.productid=" + Convert.ToInt32(e.CommandArgument.ToString()) + " and tl.UserId=" + Convert.ToInt32(Session["UserId"].ToString()) + " ", con);
                ds = new DataSet();
                da.Fill(ds, "tbl_tpd");
                if (ds.Tables.Count > 0 && ds.Tables["tbl_tpd"].Rows.Count > 0)
                {
                    da = new SqlDataAdapter("update rsa_addtocart set UserId=" + Convert.ToInt32(Session["UserId"].ToString()) + ",productid=" + Convert.ToInt32(ds.Tables[0].Rows[0][0].ToString()) + ",productname='" + ds.Tables[0].Rows[0][1].ToString() + "',ProductImage='" + ds.Tables[0].Rows[0][3].ToString() + "',price=" + Convert.ToDecimal(ds.Tables[0].Rows[0][2].ToString()) + ",cdate=getdate() where productid=" + Convert.ToInt32(ds.Tables[0].Rows[0][0].ToString()) + " and cartId=" + Convert.ToInt32(ds.Tables[0].Rows[0][5].ToString()) + " and UserId=" + Convert.ToInt32(Session["UserId"].ToString()) + " ", con);
                    da.SelectCommand.ExecuteNonQuery();
                }
            }
            else
            {
                da = new SqlDataAdapter("select tpd.ProductID,tpd.ProductName,tpd.Price,tpd.ProductImage from rsa_ProductItemTable  tpd where tpd.ProductID=" + Convert.ToInt32(e.CommandArgument.ToString()) + " ", con);
                ds = new DataSet();
                da.Fill(ds, "tbl_tpd");
            }
            if (ds.Tables.Count > 0 && ds.Tables["tbl_tpd"].Rows.Count > 0)
            {
                da = new SqlDataAdapter("insert into rsa_addtocart(UserId,productid,productname,ProductImage,price,totalcost,cdate)values(" + Convert.ToInt32(Session["UserId"].ToString()) + "," + Convert.ToInt32(ds.Tables[0].Rows[0][0].ToString()) + ",'" + ds.Tables[0].Rows[0][1].ToString() + "','" + ds.Tables[0].Rows[0][3].ToString() + "'," + Convert.ToDecimal(ds.Tables[0].Rows[0][2].ToString()) + ",1," + Convert.ToDecimal(ds.Tables[0].Rows[0][2].ToString()) + ",getdate())", con);
                da.SelectCommand.ExecuteNonQuery();
            }

        }
Addtocart.aspx

    <asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" GridLines="None" DataKeyNames="productid"
        Style="position: static" AutoGenerateColumns="False" OnRowDeleting="GridView1_RowDeleting" OnPageIndexChanging="GridView1_PageIndexChanging" AllowPaging="True" PageSize="5">
        <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <RowStyle BackColor="#EFF3FB" />
        <EditRowStyle BackColor="#2461BF" />
        <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
        <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
        <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
        <AlternatingRowStyle BackColor="White" />
        <Columns>
        
        <asp:TemplateField HeaderText="CartId">
        <ItemTemplate>
        <asp:Label ID="cartid" runat="server" Text='<%#Eval("cartId") %>'></asp:Label>
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="Image">
        <ItemTemplate>
        <asp:Image ID="imgpath" runat="server" Width="100" Height="100" ImageUrl='<%#Eval("ProductImage") %>' />
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="ProductName">
        <ItemTemplate>
        <asp:Label ID="bname" runat="server" Text='<%#Eval("productname") %>'></asp:Label>
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="Price">
        <ItemTemplate>
        <asp:Label ID="cost" runat="server" Text='<%#Eval("price") %>'></asp:Label>
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="Quantity">
        <ItemTemplate>
        <asp:TextBox ID="qty" runat="server" Width="20" Text='<%#Eval("qty") %>' AutoPostBack="True" OnTextChanged="qty_TextChanged"></asp:TextBox>
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="Total">
        <ItemTemplate>
        <asp:Label ID="tcost" runat="server" Width="100" Text='<%#Eval("totalcost") %>'></asp:Label>
        </ItemTemplate>
        </asp:TemplateField>
        
        <asp:TemplateField HeaderText="Delete">
        <ItemTemplate>
        <asp:LinkButton ID="delete" runat="server" Text="Delete" CommandName="Delete" CommandArgument='<%#Eval("cartId") %>'></asp:LinkButton>
        </ItemTemplate>
        </asp:TemplateField>
        
        </Columns>
        <EmptyDataTemplate>
            <strong>There are no items in your cart.</strong>
        </EmptyDataTemplate>
    </asp:GridView>
Addtocart.aspx.cs
<pre lang="cs">protected void Page_Load(object sender, EventArgs e)
  {
      if (Page.IsPostBack != true)
      {

          GetUserSelectedproducts(Convert.ToInt32(Session["UserId"].ToString()));
          GetTotal();
      }
  }
<pre>private void GetUserSelectedproducts(int uid)
    {
        da = new SqlDataAdapter("select tatc.cartId,tatc.productname,tatc.ProductImage,tatc.price,tatc.totalcost from rsa_addtocart tatc inner join rsa_Users tl on tl.UserId=tatc.UserId where tatc.UserId=" + uid + " ", con);
        ds = new DataSet();
        da.Fill(ds, "tbl_tatc");
        GridView1.DataSource = ds.Tables["tbl_tatc"].DefaultView;
        GridView1.DataBind();
    }
</pre>