c# check google chrome extension

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C#

Google

chrome

i cannot find any related question/solution at google, trying my luck here.
i want to check either user already install the chrome extension or not. here by i got 2 ideas.

1. Use code behind directly check their chrome's extension, which i not sure it's possible or not. if any of you have the code, please share with us :)

System.Web.HttpBrowserCapabilities browser = Request.Browser;
if (browser.Browser == "chrome")
  {
    //check for extension, if not found, alert user; if found, ignore.
  }

2. Use javascript to alert the message to user.
"OK" to redirect the user to the download page.
"Cancel" to close the dialog box. By doing this, user will get annoying, because the message will appear everytime user load the page even they already install the extension.

2-1. enhance from idea No. 2. System store the ip address which already install the extension. if the ip address is not found inside the database, dialog box shown. problem is, which phase should system store the ip address? right after user press the "OK" button at dialog box? user manually update the field? or cookies? (i never used cookies before).

Please advice :)