Set DropDownList selected value in Label in ASP.Net GridView using C#

Hello,

I have label control inside of gridview row, but I cannot seem to find to find any of them in the serverside window. The labels have runat="server" attribute,  but not recognised. The name does not exist in the current context.

<asp:GridView ID="Gridview2" runat="server" Font-Size="10pt" HeaderStyle-Font-Size="10pt" CellPadding="6" GridLines="None" ShowFooter="True" AutoGenerateColumns="False" HeaderStyle-Font-Bold="false"
     Style="width: 100%" FooterStyle-BackColor="#fdfdfd" HeaderStyle-ForeColor="#000000" Height="50px" HeaderStyle-Height="10px">
     <Columns>
         <asp:TemplateField HeaderText="Column1" ItemStyle-Width="40%" HeaderStyle-Font-Bold="false">
             <ItemTemplate>
                 <asp:TextBox ID="textBox1" runat="server" Class="form-control" Width="100%" Font-Size="10pt" Style="overflow: hidden; text-transform: capitalize; resize: none;" oninput="Resize(this)" />
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Column2" ItemStyle-Width="10%" HeaderStyle-Font-Bold="false">
             <ItemTemplate>
                 <asp:TextBox CssClass="form-control" ID="txtQuantity" Font-Size="10pt" runat="server" Width="100%" />
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Column3" ItemStyle-Width="25%" HeaderStyle-Font-Bold="false">
             <ItemTemplate>
                 <asp:Label runat="server" ID="hero-lbl" Style="font-weight: 400;"></asp:Label>
                 <asp:TextBox ID="TxtBx" runat="server" Font-Size="10pt" Width="90%" placeholder="0.00" />
             </ItemTemplate>
         </asp:TemplateField>
         <asp:TemplateField HeaderText="Column4" ItemStyle-Width="50%" HeaderStyle-Font-Bold="false">
             <ItemTemplate>
                 <asp:Label class="c-info" runat="server" ID="Infolabel" Style="font-weight: 400;"></asp:Label>
             </ItemTemplate>
         </asp:TemplateField>
     </Columns>
</asp:GridView>

<asp:DropDownList ID="DropDown1" runat="server" CssClass="form-control" 
    AutoPostBack="true" OnSelectedIndexChanged="SelectedIndexChanged">
</asp:DropDownList>

protected void SelectedIndexChanged(object sender, EventArgs e)
{
    LabelSymbol.Text = DropDown1.SelectedItem.Value.ToString();
    DropDown1.SelectedItem.Text = DropDown1.SelectedItem.Text.ToString();
    hero-lbl.Text = DropDown1.SelectedItem.Value.ToString();
    Infolabel.Text = DropDown1.SelectedItem.Value.ToString();
}