private string GetManifestFile(UrlHelper url, out string newChecksum)
{
string leadComment = $"App Version: {GetType().Assembly.GetName().Version}", cachePart = "", networkPart = "*", fallbackPart = "";
leadComment = $"{leadComment}, Timestamp: {DateTime.Now.ToString("MMMM dd, yyyy H:mm:ss")}";
var imgFolder = new DirectoryInfo(Server.MapPath("~/Content/Images"));
var imgNames = GetFileNames(imgFolder);
cachePart = string.Join(Environment.NewLine, imgNames.Select(img => url.Content($"~/Content/Images/{img}")));
//cachePart = $"{cachePart}\n" + "http://cdtssql353d:8000/t/Horizon/views/CopaycardSuite_NIAD/2_CopaysandCostImpact?&isdebug=true";
var manifestContent = $"CACHE:\n{cachePart}\n\nNETWORK:\n{networkPart}\n\nFALLBACK:\n{fallbackPart}";
var checksum = ChecksumHelper.GetMD5Checksum(manifestContent);
newChecksum = checksum;
var manifestFile = $"CACHE MANIFEST\n# {leadComment}, Checksum: {ChecksumHelper.GetMD5Checksum(manifestContent)}\n\n{manifestContent}";
return(manifestFile);
}