protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {//Тут e.NewValues содержит старые значения
            Global.medication.Find(m=>m.id == Convert.ToInt32(e.NewValues["id"])).set(string.Format("{0}", e.NewValues["name"]),
                Convert.ToDouble(string.Format("{0}", e.NewValues["price"])));
            GridView1.EditIndex = -1;
            GridView1.DataBind();
        }

    <asp:GridView ID="GridView1" AutoGenerateColumns="false" runat="server" 
        onrowcancelingedit="GridView1_RowCancelingEdit" 
        onrowdeleting="GridView1_RowDeleting" onrowediting="GridView1_RowEditing" 
        onrowupdating="GridView1_RowUpdating" DataKeyNames="id">
        <EmptyDataTemplate>Данных нет</EmptyDataTemplate>
        <Columns>
            <asp:BoundField DataField="id" ItemStyle-CssClass="hidden" HeaderStyle-CssClass="hidden" />
            <asp:BoundField HeaderText="Название" DataField="name"/>
            <asp:BoundField HeaderText="Цена (грн)" DataField="price"/>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:HyperLink DataField="index" Text="Наличие в аптеках" NavigateUrl='<%# "default.aspx?p=" + Eval("id") %>' runat="server"></asp:HyperLink>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>