ASP.NET FAQ - Output Caching

Output caching lets you cache the output of static aspx pages or portions of pages to improve performance. Since the pages are cached asp.net doesn’t have to regenerate the html for every request.

For more information see:

• Output Caching Techniques In ASP.NET

No, not easily unless you use the output cache APIs on Response.Cache and take advantage of the Response.AddCacheDependency() to make the page dependent on a common key.

Then, from the other page or class you could invalidate the common key which would enforce a dependency eviction (since the key page1 depended on changed).
Refer How to remove OutputCache by param?

Try using ‘HttpContext.Current.Cache’ instead of just ‘Cache’ in your code. The compiler probably wasn’t able to resolve the Cache type.

Try the following:

<%@ OutputCache Duration='10' VaryByParam='*' %> 

This should result in any changes to querystring parameters causing a new version of the page to be cached. Keep in mind that this can significantly increase the amount of memory used for caching, depending on how many querystring parameters you’re using.
Note: ‘*’ is not recommended – it is best to use a list of params that your page truly varies by.

Try VaryByCustom=’browser’ in the user control/page.

You can attach a cache dependency to the response that is unique per query param, then invalidate the dependency for that particular param:

// add cache item dependency on response 
string cacheKey = 'xxx.aspx?' + queryParam; 
Cache[cacheKey] = new object(); 
Response.AddCacheItemDependency(cacheKey); 

// invalidate the dependency 
string cacheKey = 'xxx.aspx?' + queryParam; 
Cache.Remove(cacheKey); 

Let’s say you set your output cache directive as follows:

<%@ OutputCache Duration='86400' VaryByParam='RegionID' VaryByCustom='ProductID' %>

VaryByCustom – is a string that your application has to interpret in the GetVaryByCustomString override in the gloabal.asax file.

Now, to avoid caching pages for certain ProductIDs you can set the cacheability to private or nocache from your page load for those pages as follows:

VB.NET

Response.Cache.SetCacheability(HttpCacheability.Private) 

C#

Response.Cache.SetCacheability(HttpCacheability.Private) ;

Yes. In your page:

<%@ OutputCache Duration='60' VaryByParams='abc;xyz' VaryByCustom='browsermajorversion' %> 

In your global.asax file:

VB.NET

Public Overrides Function GetVaryByCustomString(context As HttpContext, custom As String) As String
	If custom.ToLower() = 'browsermajorversion' Then
		Dim browser As HttpBrowserCapabilities = context.Request.Browser
			Return browser.Browser + ' ' + browser.MajorVersion
	Else
		Return MyBase.GetVaryByCustomString(context, custom)
	End If
End Function ’GetVaryByCustomString

C#

public override string GetVaryByCustomString(HttpContext context, string custom)
{ 
	if (custom.ToLower() == 'browsermajorversion') { 
		HttpBrowserCapabilities browser = context.Request.Browser; 
		return browser.Browser + ' ' + browser.MajorVersion; 
	} 
	else 
	{ 
	return base.GetVaryByCustomString(context, custom); 
	} 
} 

<%@OutputCache ... VaryByHeader='UserAgent' %>

or

<%@ OutputCache ... VaryByHeader='Accept-Language' %>

You can use tag

<%@ OutputCache Duration='0' Location='None' VaryByParam='none' %> 

or

VB.NET

Response.Cache.SetCacheability(HttpCacheability.NoCache)

C#

Response.Cache.SetCacheability(HttpCacheability.NoCache);

Try the following:

<%@ OutputCache location='none' %>

You can attach a cache dependency to the response that is unique per query param, then invalidate the dependency for the particular param:

VB.NET

’add cache item dependency on response 
Dim cacheKey As String = 'webform1.aspx?' + queryParam
Cache(cacheKey) = New Object() ’
Response.AddCacheItemDependency(cacheKey)

’ invalidate the dependency 
Dim cacheKey As String = 'webform1.aspx?' + queryParam
Cache.Remove(cacheKey)

C#

// add cache item dependency on response 
string cacheKey = 'webform1.aspx?' + queryParam; 
Cache[cacheKey] = new object(); 
Response.AddCacheItemDependency(cacheKey); 

// invalidate the dependency 
string cacheKey = 'webform1.aspx?' + queryParam; 
Cache.Remove(cacheKey); 

VB.NET

Dim enumerator As IDictionaryEnumerator = Cache.GetEnumerator()
While enumerator.MoveNext()
	Dim key As String = CType(CType(enumerator.Current, DictionaryEntry).Key, String)
	If key.StartsWith('cachedata_') Then
	                ’ Print it:
                	Response.Write(('Deleting key ' + key + '
'))
	                ’ Remove it:
                	Cache.Remove(key)
	End If
End While

C#

IDictionaryEnumerator enumerator = Cache.GetEnumerator();
while(enumerator.MoveNext()) 
{
	String key = (String) ((DictionaryEntry) enumerator.Current).Key;
	if(key.StartsWith('cachedata_')) 
	{
		// Print it:
		Response.Write('Deleting key ' + key + '
');
		// Remove it:
		Cache.Remove(key);
	}
}

VB.NET

Dim objItem As DictionaryEntry
For Each objItem In  Cache
   ’Response.Write (objItem.Key.ToString ());
   Cache.Remove(objItem.Key.ToString())
Next  

C#

foreach(DictionaryEntry objItem in Cache) 
{ 
	//Response.Write (objItem.Key.ToString ());
	Cache.Remove(objItem.Key.ToString () ) ;
}

VB.NET

Dim objItem As DictionaryEntry
For Each objItem In  Cache
   	Response.Write(('Key :' + objItem.Key.ToString() + '
'))
   	Response.Write((' Value :' + objItem.Value.ToString() + '
'))
Next 

C#

foreach(DictionaryEntry objItem in Cache) 
{ 
	Response.Write ('Key :' + objItem.Key.ToString () + '
');
	Response.Write(' Value :' + objItem.Value.ToString ()+ '
' ) ;
}

VB.NET

somevar=System.Web.HttpContext.Current.Cache('')

C#

somevar=System.Web.HttpContext.Current.Cache('');

Use namespace System.Web.Caching or
refer to it as System.Web.Caching.CacheDependency

Use HttpRuntime.Cache

You could add a dependency to the output cached control, and change the dependency to evict the control. Here’s code to do that:

VB.NET

If TypeOf Parent Is System.Web.UI.BasePartialCachingControl Then
            	Cache('dependent') = 'dependent'
            	Dim dep As New CacheDependency(Nothing, New String() {'dependent'}) ’
            	CType(Parent, System.Web.UI.BasePartialCachingControl).Dependency = dep
End If

C#

if (Parent is System.Web.UI.BasePartialCachingControl) 
{ 
	Cache['dependent'] = 'dependent'; 
	CacheDependency dep = new CacheDependency(null, new string[] 'dependent'); 
	((System.Web.UI.BasePartialCachingControl)Parent).Dependency = dep; 
} 

If the PDF files are on the disk, you should just let the IIS handle them. The IIS static file handler performs caching and is much faster than the ASP.NET cache.