using System.IO;
using System.Web;
using System.Web.Caching;
using System.Web.Hosting;

/// <summary>
/// Summary description for Fingerprint
/// </summary>
public class Fingerprint
{
    public static string Tag(string rootRelativePath)
    {
        if (HttpRuntime.Cache[rootRelativePath] == null)
        {
            var absolute = HostingEnvironment.MapPath("~" + rootRelativePath);
            if (absolute == null) return HttpRuntime.Cache[rootRelativePath] as string;
            var date = File.GetLastWriteTime(absolute);
            var result = string.Format("v={0}", date.Ticks);
            HttpRuntime.Cache.Insert(rootRelativePath, result, new CacheDependency(absolute));
        }
        return HttpRuntime.Cache[rootRelativePath] as string;
    }
}