How can I change advertisements from admin panel on my web page.

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C#

ASP.NET

XML

how can i control my advertisement from admin panel by admin user, i mean admin user can change the advertisements according to their choice from admin panel and post advertisement on anywhere on page when select a field.

like if admin select header then ad shows on a header part.
if admin select a middle part of the page than ad shows on a middle part.
if admin select footer than ad shows on a footer part of the website.

i have a given a dropdown list to the admin in admin panel for select these option.

What I have tried:

i have used these codes to built a advertisement on my website..

<asp:scriptmanager id="scriptmanager1" runat="server"></asp:scriptmanager>
<asp:timer id="timer1" runat="server" interval="2000"></asp:timer>
<asp:updatepanel id="updatepanel1" runat="server">
     <triggers>
        <asp:asyncpostbacktriggers controlid="timer1" eventname="tick"/>
     <triggers>
     <contenttemplate>
         <asp:adrotator id="adrotator1" runat="server" 
          advertisementfile="~/advertisement.xml"/>
     </contenttemplate>
</asp:updatepanel>

here is my xmlfile for change the advertisement on webpage..

<?xml version="1.0" encoding="utf-8" ?>
<Advertisements>
   <Ad>
      <ImageUrl>~/admages/magnifying-glass-76520_1280.png</ImageUrl>
      <NavigateUrl>http://www.google.com</NavigateUrl>
      <AlternateText>
         please visit google.com
      </AlternateText>
      <Impressions>20</Impressions>
      <Keyword>google</Keyword>
   </Ad>

   <Ad>
      <ImageUrl>~/admages/youtube-2712573_1280.png</ImageUrl>
      <NavigateUrl>http://www.youtube.com</NavigateUrl>
      <AlternateText>please visit youtube.com</AlternateText>
      <Impressions>30</Impressions>
      <Keyword>google</Keyword>
   </Ad>
  
</Advertisements>

but i want to change this advertisement from admin panel by admin user..
i have designed a page in admin panel by using 3 textboxes and one submit button.
Banner Url Textbox1
Link To Textbox2
Alternate Text Textbox3

submit button

but the problem is i have no idea how can i do this, if anyone have a solution about this please help me as soon as possible and thanks in advance