Include ASP packages in offline cache (#5124)

* Archive asp.net package references

* Archive asp.net package references

* Change the hash input so it's the same on all platforms

* Address PR comments

build_projects/dotnet-cli-build/GenerateNuGetPackagesArchiveVersion.cs

@@ -0,0 +1,75 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Build.Construction;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+using System;
+using System.IO;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Microsoft.DotNet.Cli.Build
+{
+    public class GenerateNuGetPackagesArchiveVersion : Task
+    {
+        public GenerateNuGetPackagesArchiveVersion()
+        {
+        }
+
+        [Required]
+        public string RepoRoot { get; set; }
+
+        [Output]
+        public String Version { get; set; }
+
+        public override bool Execute()
+        {
+            var webTemplatePath = Path.Combine(
+                RepoRoot,
+                "src",
+                "dotnet",
+                "commands",
+                "dotnet-new",
+                "CSharp_Web",
+                "$projectName$.csproj");
+
+            var rootElement = ProjectRootElement.Open(webTemplatePath);
+            var packageRefs = rootElement.Items.Where(i => i.ItemType == "PackageReference").ToList();
+
+            var dataToHash = string.Empty;
+            foreach (var packageRef in packageRefs)
+            {
+                dataToHash += $"{packageRef.Include},";
+                if (packageRef.HasMetadata)
+                {
+                    foreach (var metadata in packageRef.Metadata)
+                    {
+                        dataToHash += $"{metadata.Name}={metadata.Value};";
+                    }
+                }
+            }
+
+            Log.LogMessage($"NuGet Packages Archive Data To Hash: '{dataToHash}'");
+
+            var sha256 = SHA256.Create();
+            var hashBytes = sha256.ComputeHash(Encoding.Unicode.GetBytes(dataToHash));
+            Version = GetHashString(hashBytes);
+
+            Log.LogMessage($"NuGet Packages Archive Version: '{Version}'");
+
+            return true;
+        }
+
+        private string GetHashString(byte[] hashBytes)
+        {
+            StringBuilder builder = new StringBuilder(hashBytes.Length * 2);
+            foreach (var b in hashBytes)
+            {
+                builder.AppendFormat("{0:x2}", b);
+            }
+            return builder.ToString();
+        }
+    }
+}