HtmlAgilityPack is a library for parsing HTML content, it is not used for client - server interactions. So in short you cannot submit a forms with it.
But you can create a submission request yourself with a
WebRequest class[
^].
If I were you, I would investigate the request that browser sends when you submit a form on that particular website that you are targeting, for example you could use
Fiddler[
^] for this. After that you can use WebRequest.Create method and set the required headers, post data, etc. on that request. After that you can get the response, that browser gets when the user submit the form, and I would load that response in HtmlAgilityPack for further processing.
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