Basics
- An HTTP Handler is a .NET class that executes whenever you make a request for a file at a certain path.
- The Page class is an HTTP Handler because it implements the IHttpHandler interface.
- The IsReusable property indicates whether ASP.NET can keep the handler in memory to service multiple requests, or if it must create a new instance of the handler for every request.
- Unless you maintain some sort of state in the handler, which is uncommon, IsReusable should always return true.
- Two ways to create an HTTP Handler:
- Generic Handler (.ashx): you cannot execute a Generic Handler whenever someone requests a file with the extension .gif. If you need more control over when an HTTP Handler executes, create a class implements IHttpHandler.
- Custom class implement the IHttpHandler interface.
Class implements IHttpHandler
- Register HTTP Handlers & Configure HTTPHandler Extension in IIS.
- IIS 6.0
- In the httpHandlers section of the web.config, add an entry for the file-name extension. Specify the following four attributes:
- path: specify the path associated with the handler.
- verb: specify the HTTP verbs, such as GET or POST, associated with the handler. You can specify multiple verbs in a comma-separated list. You can represent any verb with the * wildcard.
- type: specify the name of the class that implements the handler.
- validate: specify whether the handler is loaded during application startup. When true, the handler is loaded at startup. When false, the handler is not loaded until a request associated with the handler is made.
- add the file extension to map to Aspnet_isapi.dll
- Verify that file exists check box
- Check. The file-name extension represents a physical file in the application. If the requested file does not exist on disk, IIS displays an error.
- Uncheck. The file-name extension does not represent a physical file. Instead, the extension is handled dynamically by a class that is mapped to the extension in ASP.NET.
- IIS 7.0 (Classic or Integrated mode)
- Using IIS Manager in IIS 7.0 to add a custom handler extension is equivalent to registering the handler extension in the Web.config file of an ASP.NET application. The registration adds a handler element in the handlers section of the system.webServer group.
- In the httpHandlers section of the web.config, add an entry for the file-name extension.
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