Did you know you can prevent the revalidation of files in browser cache and subsequent 304 response by completely removing both the ETag and Last-Modifed response headers?
Of course, this is easy in Apache, but as clear as mud in IIS 6. Does anyone know how to remove both of these headers in IIS?
A programmatic way is to use a HTTP module, something like this (based on a SO answer by Luke):
namespace HttpModules
{
using System;
using System.Web;
public class RemoveExtraneousHeaderModule : IHttpModule
{
/// <summary>
/// Initializes a module and prepares it to handle requests.
/// </summary>
/// <param name="context">Provides access to the request context.</param>
public void Init(HttpApplication context)
{
context.PreSendRequestHeaders += this.OnPreSendRequestHeaders;
}
/// <summary>
/// Disposes of the resources (other than memory) used by this module.
/// </summary>
public void Dispose()
{
}
/// <summary>
/// Event raised just before ASP.NET sends HTTP headers to the client.
/// </summary>
/// <param name="sender">Event source.</param>
/// <param name="e">Event arguments.</param>
protected void OnPreSendRequestHeaders(object sender, EventArgs e)
{
NameValueCollection headers = HttpContext.Current.Response.Headers;
headers.Remove("Server");
headers.Remove("ETag");
headers.Remove("X-Powered-By");
headers.Remove("X-AspNet-Version");
headers.Remove("X-AspNetMvc-Version");
}
}
}
The module gets installed via web.config, under <system.web>
for IIS 6 and under <system.webServer>
for IIS 7.
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