Shows very basic downloading using async/await

sample downloader.linq

<Query Kind="VBProgram">
  <Reference>&lt;RuntimeDirectory&gt;\Microsoft.VisualBasic.dll</Reference>
  <Reference>&lt;RuntimeDirectory&gt;\System.Net.Http.dll</Reference>
  <Namespace>Microsoft.VisualBasic</Namespace>
  <Namespace>System.Net.Http</Namespace>
  <Namespace>System.Threading.Tasks</Namespace>
</Query>

Async Sub Main
	Dim client As New HttpClient

	Dim urls As String() = {
	"https://geolite.maxmind.com/download/geoip/database/GeoLite2-City-CSV.zip",
	"https://raw.githubusercontent.com/matthewreagan/WebstersEnglishDictionary/master/dictionary.json"
	}

	' client.GetByteArrayAsync(u) creates a task that is started right away.  So the bytes are being downloaded right when it is called.
	' So I am getting an array of objects that have a url and a Download property that is the download task
	Dim downloads = urls.Select(Function(u) New With {.Url = u, .Download = client.GetByteArrayAsync(u)}).ToArray

	downloads.Dump("Downloads")

	Console.WriteLine("Files are downloading and awaiting all downloads here.")

	' Files are downloading.  This await creates a task that will continue the rest of main when all the downloads complete.
	Await Task.WhenAll(downloads.Select(Function(d) d.Download))

	Console.WriteLine("Downloads are complete.")
	'Downloads have completed.  Since I am using linq I can't use await in the lambda.  So I am getting the result property.  
	' The tasks have completed since we are in the continuation of the above await.
	' Creates a projection from the tasks and creates an array of byte arrays.  Dim data as byte()()
	Dim data = downloads.Select(Function(d) d.download.Result).ToArray

	'Create a projection from the byte arrays showing the size of each array.
	' Notice that this does not show till the downloads complete
	data.Select(Function(bd) New With {
		.Size=bd.Length,
		.Hash=String.Join("",array.ConvertAll(Sha512(bd),Function(b) b.ToString("X2")))
	}).Dump("Downloaded Data sizes")
	
	


End Sub

' Define other methods and classes here
Function Sha512(bytes As Byte()) As Byte()
	Static sha As System.Security.Cryptography.SHA512Managed = System.Security.Cryptography.SHA512Managed.Create()
	
	Return sha.ComputeHash(bytes)
	
	End Function

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