How to: Set Cache Policy for a Request

The following example demonstrates setting a cache policy for a request. The example input is a URI such as https://www.contoso.com/.

Example

The following code example creates a cache policy that allows the requested resource to be used from the cache if it has not been in the cache for longer than one day. The example displays a message that indicates whether the resource was used from the cache—for example, "The response was retrieved from the cache : False."—and then displays the resource. A request can be fulfilled by any cache between the client and server.

using System;
using System.Net;
using System.Net.Cache;
using System.IO;

namespace Examples.System.Net.Cache
{
    public class CacheExample
    {   
        public static void UseCacheForOneDay(Uri resource)
        {
            // Create a policy that allows items in the cache
            // to be used if they have been cached one day or less.
            HttpRequestCachePolicy requestPolicy = 
                new HttpRequestCachePolicy (HttpCacheAgeControl.MaxAge,
                TimeSpan.FromDays(1));
            
            WebRequest request = WebRequest.Create (resource);
            // Set the policy for this request only.
            request.CachePolicy = requestPolicy;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            // Determine whether the response was retrieved from the cache.
            Console.WriteLine ("The response was retrieved from the cache : {0}.",
               response.IsFromCache);
            Stream s = response.GetResponseStream ();
            StreamReader reader = new StreamReader (s);
            // Display the requested resource.
            Console.WriteLine(reader.ReadToEnd());
            reader.Close ();
            s.Close();
            response.Close();
        }
        public static void Main(string[] args)
        {
            if (args == null || args.Length != 1)
            {
                Console.WriteLine ("You must specify the URI to retrieve.");
                return;
            }
            UseCacheForOneDay (new Uri(args[0]));
        }
    }
}

Imports System
Imports System.Net
Imports System.Net.Cache
Imports System.IO
Namespace Examples.System.Net.Cache
    Public Class CacheExample
        Public Shared Sub UseCacheForOneDay(ByVal resource As Uri)
            ' Create a policy that allows items in the cache
            ' to be used if they have been cached one day or less.
            Dim requestPolicy As New HttpRequestCachePolicy _
                  (HttpCacheAgeControl.MaxAge, TimeSpan.FromDays(1))
            Dim request As WebRequest = WebRequest.Create(resource)
            ' Set the policy for this request only.
            request.CachePolicy = requestPolicy
            Dim response As HttpWebResponse = _
             CType(request.GetResponse(), HttpWebResponse)
            ' Determine whether the response was retrieved from the cache.
            Console.WriteLine("The response was retrieved from the cache : {0}.", _
                response.IsFromCache)
            Dim s As Stream = response.GetResponseStream()
            Dim reader As New StreamReader(s)
            ' Display the requested resource.
            Console.WriteLine(reader.ReadToEnd())
            reader.Close()
            s.Close()
            response.Close()
        End Sub
        Public Shared Sub Main(ByVal args() As String)
            If args Is Nothing OrElse args.Length <> 1 Then
                Console.WriteLine("You must specify the URI to retrieve.")
                Return
            End If
            UseCacheForOneDay(New Uri(args(0)))
        End Sub
    End Class
End Namespace

See Also

Reference

<requestCaching> Element (Network Settings)

Concepts

Cache Policy
Location-Based Cache Policies
Time-Based Cache Policies

Other Resources

Cache Management for Network Applications