public partial class _Default : System.Web.UI.Page
protected void Page_Load(object sender, EventArgs e)
DateTime contentModified = System.IO.File.GetLastWriteTime("C:\\image.jpg");
if (IsClientCached(contentModified))
HttpContext.Current.Response.StatusCode = 304;
HttpContext.Current.Response.SuppressContent = true;
HttpContext.Current.Response.Cache.SetLastModified(contentModified);
private bool IsClientCached(DateTime contentModified)
string header = HttpContext.Current.Request.Headers["If-Modified-Since"];
DateTime isModifiedSince;
if (DateTime.TryParse(header, out isModifiedSince))
return isModifiedSince > contentModified;