So I used Nuget to get the Fizzler package and it brought down the HTML agility pack, but now I have a compilation error when trying to use the library
The type or namespace name 'Systems' does not exist in the namespace 'Fizzler'
package.config contains
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
    <package id="Fizzler" version="1.0.0" targetFramework="net45" />
    <package id="HtmlAgilityPack" version="1.4.9.5" targetFramework="net45" />
 </packages>
I was trying to call an HTML5 CSS3 selector method QuerySelectorAll but it gives error message ... error CS1061: 'HtmlAgilityPack.HtmlNode' does not contain a definition for 'QuerySelectorAll' and no extension method 'QuerySelectorAll' accepting a first argument of type 'HtmlAgilityPack.HtmlNode' could be found (are you missing a using directive or an assembly reference?)
 
  
                     
                        
Despite your comment, it looks like you need the Fizzler.System.HtmlAgilityPack package. You should then be able to use:
using Fizzler.System.HtmlAgilityPack;
... at which point the extension methods in HtmlNodeSelection (including QuerySelectorAll) will be available.
 
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