C# Online Compiler | .NET Fiddle

<no name> by Anonymous

using System;
using HtmlAgilityPack;
using System.Xml;
					
public class Program
{
	public static void Main()		
	{
		string html = "<html><body><h3><a style=\"display:none\" href=\"/aclk?sa=L&ai=DChcSEwimnPnc5OvQAhWRl70KHcxqCEAYABAA&ei=9hZNWLqlCIyY8gXA04vACg&sig=AOD64_3SZuXd57_-qOs8nnhn8rqw8GlIgw&q=&sqi=2&ved=0ahUKEwi6-PTc5OvQAhUMjLwKHcDpAqgQ0QwIGA&adurl=\" id=\"s0p1c0\"></a><a href=\"https://www.google.co.jp/aclk?sa=L&ai=DChcSEwimnPnc5OvQAhWRl70KHcxqCEAYABAA&ei=9hZNWLqlCIyY8gXA04vACg&sig=AOD64_3SZuXd57_-qOs8nnhn8rqw8GlIgw&q=&sqi=2&ved=0ahUKEwi6-PTc5OvQAhUMjLwKHcDpAqgQ0QwIGA&adurl=\" id=\"vs0p1c0\" onmousedown=\"return google.arwt(this)\" data-preconnect-urls=\"http://www.hundsun.co.jp/\" jsl=\"$t t-zxXzjt1d4B0;$x 0;\" class=\"r-iA_xzYkgkx2Y\">ブリッジSE募集中 - hundsun.co.jp‎</a></h3></body></html>";
		HtmlDocument doc = new HtmlDocument();
		doc.LoadHtml(html);
		var links = doc.DocumentNode.SelectNodes("//a[@data-preconnect-urls]");
		if (links == null) 
		{
			Console.WriteLine("no links contain attribute data-preconnect-urls");
			return;
		}
		foreach(var htmlNode in links)
		{
			var attr = htmlNode.Attributes["data-preconnect-urls"];
			Console.WriteLine(attr.Value);
		}
	}
}

 
using System;
using HtmlAgilityPack;
using System.Xml;
                    
public class Program
{
    public static void Main()       
    {
        string html = "<html><body><h3><a style=\"display:none\" href=\"/aclk?sa=L&ai=DChcSEwimnPnc5OvQAhWRl70KHcxqCEAYABAA&ei=9hZNWLqlCIyY8gXA04vACg&sig=AOD64_3SZuXd57_-qOs8nnhn8rqw8GlIgw&q=&sqi=2&ved=0ahUKEwi6-PTc5OvQAhUMjLwKHcDpAqgQ0QwIGA&adurl=\" id=\"s0p1c0\"></a><a href=\"https://www.google.co.jp/aclk?sa=L&ai=DChcSEwimnPnc5OvQAhWRl70KHcxqCEAYABAA&ei=9hZNWLqlCIyY8gXA04vACg&sig=AOD64_3SZuXd57_-qOs8nnhn8rqw8GlIgw&q=&sqi=2&ved=0ahUKEwi6-PTc5OvQAhUMjLwKHcDpAqgQ0QwIGA&adurl=\" id=\"vs0p1c0\" onmousedown=\"return google.arwt(this)\" data-preconnect-urls=\"http://www.hundsun.co.jp/\" jsl=\"$t t-zxXzjt1d4B0;$x 0;\" class=\"r-iA_xzYkgkx2Y\">ブリッジSE募集中 - hundsun.co.jp•</a></h3></body></html>";
        HtmlDocument doc = new HtmlDocument();
        doc.LoadHtml(html);
        var links = doc.DocumentNode.SelectNodes("//a[@data-preconnect-urls]");
        if (links == null) 
        {
            Console.WriteLine("no links contain attribute data-preconnect-urls");
            return;
        }
        foreach(var htmlNode in links)
        {
            var attr = htmlNode.Attributes["data-preconnect-urls"];
            Console.WriteLine(attr.Value);
        }
    }
}

View IL Code