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
Concepts
Reference
<requestCaching> Element (Network Settings)