How do I get full HTML DOM included 'GridView' information from an aspx webpage?

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C#

ASP.NET

Windows

HTML

Gridview

, +

My goal is to recover data file download information from a 'GridView' of a Web page (.aspx).
When I active the inspection function (F12) and access to URL I can see the information I need in the 'GridView' as show below:

<img name="BtnDescarga" width="25" height="25" title="Descargar" class="BtnDescarga" id="BtnDescarga" style="cursor: pointer;" >

In my application I use the WebBrowser control to navigate to the desired URL. Once there I get the HTML code using 'WebBrowser.DocummentText', but in the HTML code retrieved the information contained in 'GridView' does not appear.

I tried with another URL that contains a very similar 'GridView' and in this case the information of 'GridView' is displayed.
The difference I see between the two URLs is that in which no work is accessed through HTTPS.

How can I obtain the information contained in the 'GridView' as I get with the Inspector of elements (F12)?