The PartialCachingControl.CachedControl property always returns a null reference

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Article ID: 837000 - View products that this article applies to.
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SUMMARY

If a user control (.ascx file) contains an @ OutputCache directive, Microsoft ASP.NET automatically generates a PartialCachingControl class when the user control is requested. The PartialCachingControl class contains a CachedControl property (the PartialCachingControl.CachedControl property). You can use the CachedControl property to determine if the control was pulled from the cache or if the control was newly constructed. If the value of this property is a null reference (Nothing in Microsoft Visual Basic), the user control was pulled from the cache.  If the value of this property is not a null reference, the user control was constructed. However, if the CachedControl is not coded correctly, the CachedControl property will always return a null reference. The CachedControl property always returns a null reference unless the control has been pre-added to the control tree. Before you check the CachedControl property, add the user control to the control tree. Note the code sample that is in the "More Information" section of this article.

Note This behavior is by design. The cached control is not created until the Init phase. The control is not created until you insert the PartialCachingControl class in the control tree. For more information, see a code sample in the "More Information" section of this article.

MORE INFORMATION

The following code demonstrates that you have a user control that contains an OutPutCache directive, you can use the PartialCachingControl class to determine if the user control was pulled from the cache or if the user control was newly constructed:
void Page_Init()
 {
     Control Item;
     Item = Page.LoadControl("test1.ascx");
     Test1a.Controls.Add(Item);  // Comment this line to see the "always null" behavior.
     if ( ((PartialCachingControl)Item).CachedControl != null)
			 {
     	Response.Write("CachedControl is not null!");
     } 
			else 
		{
     Response.Write("CachedControl is null!");
   }
}

Properties

Article ID: 837000 - Last Review: March 12, 2004 - Revision: 1.3
APPLIES TO
  • Microsoft Visual Studio .NET 2003 Enterprise Architect
  • Microsoft Visual Studio .NET 2003 Enterprise Developer
  • Microsoft Visual Studio .NET 2003 Professional Edition
  • Microsoft ASP.NET 1.1
Keywords: 
kbinfo kbvalidation kbhttpruntime KB837000

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