Xml Compression tests

loadxml.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Xml;

namespace Test 
{
		class Test 
		{
			static void Main()
			{
				var stopWatch = new Stopwatch();
				stopWatch.Start();
				using(var inputStream = File.OpenRead(@"c:\junk\supp2017.xml"))
				{
					var doc = new XmlDocument();
				
					doc.Load(inputStream);
				}
				stopWatch.Stop();
				Console.WriteLine("Loading xml {0}", stopWatch.Elapsed.TotalMilliseconds);
				
				Console.WriteLine("Done");
			}
		}
}

loadxmldeflated.cs

using System;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;
using System.Xml;

namespace Test 
{
		class Test 
		{
			static void Main()
			{
				var stopWatch = new Stopwatch();
				stopWatch.Start();
				using(var inputStream = File.OpenRead(@"c:\junk\supp2017.xml.cmp"))
				{
					using (DeflateStream decompressingStream = new DeflateStream(inputStream, CompressionMode.Decompress))
        	    {
					var doc = new XmlDocument();
				
					doc.Load(decompressingStream);
				}
				}
				stopWatch.Stop();
				Console.WriteLine("Loading xml {0}", stopWatch.Elapsed.TotalMilliseconds);
				
				Console.WriteLine("Done");
			}
		}
}

You convinced me that XmlDocument.Load() is slow enough to be on par with the extremely slow disk I/O (especially for GB-sized documents), but still isn't slow enough to render compression worthless as you stated. So your reasoning is not completely wrong – I'm willing to remove the downvote from your answer. But this can be done only after editing it because 2+ days has elapsed. Thank you for the constructive discussion.