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.NET Data Caching
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This thread is for discussions of .NET Data Caching.
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5 years agoby
mathew.chacko
mathew.chacko
Geneva, Switzerland, United StatesJoined 5 years agoI created a class to test the data cache. Any help where to use cache?
// test.cs
//
namespace xtest {
using System;
using System.Web;
using System.Web.Caching;
public class xtest {
public static Cache srvCache = new Cache();
public xtest() {}
public static string getCache(string key){
try {
object strServer= 0;
if (srvCache["ServerString"] == null)
srvCache["ServerString"]=key;
strServer = srvCache.Get("ServerString");
return (string) strServer;
}
catch (Exception e)
{
return "error: getCache() - "+ e.Message;
}
}
}
}
When I run the below mentioned aspx. I get error:
- Object reference not set to an instance of an object.
<%@ Page Language="C#" %>
<%@ import Namespace="xtest" %>
<script runat="server">
void Page_Load(object sender, EventArgs e) {
Response.Write(xtest.getCache("X-STAGE"));
}
</script>
<html>
<head>
</head>
<body>
<form runat="server">
<!-- Insert content here -->
</form>
</body>
</html>
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On what line does the error occur?
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How would one use the .NET cache object to keep caches accurate across processes?
--Charlie -
Yes I have tried that as well. IMHO: The thing is that you are trying to access a cache object from a class. But the documentation says that the Cache object cannot be inherited. therefore I would expect it to throw a "Cache is not available" exception. Now this is a real bugger specially when you want to cache data across process/pages. This is precisely what I'm trying to do right now and I have yet to find a solution. Help anyone?
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Hi all, this article unfortunately doesn't deal with class caching. However, in my latest article posted here on DeveloperFusion -Building a Full-Featured Custom DataGrid Control - I do just that. I demonstrate how to cache an object, in this case the Datagrid, within a class using either the Session or Web Cache API.
As for caching across processes, you'll need to use .NET remoting. The process is discussed here The process is discussed here Using Remoting Singleton Caching.
Hope this helps.
-DM -
Hi Charlie,
You can use .NET remoting when you need to keep your cache across processes. The process is discussed here Using Remoting Singleton Caching.
Hope this helps.
-DM -
I stumbled into this problem. The comment is correct The Cache class is a sealed class, which means it cannot be inherited. Since you are inheriting the Page class in your X testClass the Cache object will not be available. One way to solve the problem is to pass the Cache object of the Page to the Method that need to process the Cache information as shown in the Sample code..
<%@ import Namespace="Env" %>
<%@ import Namespace="System.Xml" %>
<%@ Page Language="C#" Inherits ="Env.ServerProcess" %>
<%
XmlDocument xDoc = new XmlDocument();
xDoc=ProcessRequest(Request.InputStream,this.Cache);
Response.ContentType="text/xml";
Response.Write (xDoc.OuterXml);
%>
public class ServerProcess : System.Web.UI.Page
{
public XmlDocument ProcessRequest(Stream PageRequestStream,Cache MyCache)
{
string sResetClientId="";
XmlDocument xdoc =new XmlDocument();
try{
if (MyCache ["ResetClientDoc"] == null){
TextReader xt=new StreamReader(Server.MapPath(@"Content/ResetClientID.xml"));
sResetClientId=xt.ReadToEnd();
xt.Close();
MyCache dep = new CacheDependency(Server.MapPath(@"Content/ResetClientID.xml"), DateTime.Now);
MyCache.Insert("ResetClientDoc", sResetClientId, dep);}
Else
{
sResetClientId=(string) MyCache ["ResetClientDoc"];
}
}
catch (Exception e){
System.Diagnostics.Debug.WriteLine( e.Message.ToString())
}
xdoc.LoadXml(sResetClientId);
return xdoc;
} -
Just because the Cache cannot be inherited, doesn't mean you can't access it when you are inheriting the Page class -
public class MyClass : System.Web.UI.Page {
public Object SomeMethod() {
return Cache["SomeObject"];
}
}
is fine. As it's sealed, what you can't do is this:
public class MyClass : Cache {
// override or add some methods here
} -
So , Does That mean this is a Genuine Microsoft Bug??
No matter What If I Use this Syntax[ Colorede red] to acess the Cache Object I get an Exception...
internal class EnvUtil
ystem.Web.UI.Page {
internal EnvUtil()
{
}
internal string ResetClientID
{
get
{
string sResetClientId="";
try
{
if (Cache["ResetClientDoc"] == null) {
TextReader xt=new StreamReader(Server.MapPath(@"../../Content/EnvReport/ResetClientID.xml"));
sResetClientId=xt.ReadToEnd();
xt.Close();
CacheDependency dep = new CacheDependency(Server.MapPath(@"../../Content/EnvReport/ResetClientID.xml"), DateTime.Now);
Cache.Insert("ResetClientDoc", sResetClientId, dep);
}
else
{
sResetClientId=(string) Cache["ResetClientDoc"];
}
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
return sResetClientId;
}
}
}
}
Output
?ex.Message
"Cache is not available" -
To Access the Pages Cache from class code c#
Cache ce = new Cache();
ce = System.Web.HttpRuntime.Cache; Lol
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