GLOBAL.ASAX

• Used by Web Applications to handle some application-level events raised by the ASP.net runtime or by registered http modules
  
• Global.asax file is optional and is located in the root directory of the application
  
• Only one global.asax file per application is accepted, those in sub-directories are ignored
  
• When the application is started, global.asax is parsed into a source class and compiled
  
• The resultant assembly is created in the temporary directory just as any other dynamically generated assembly would be
  
• The class is named as ASP.global_asax and is derived from System.Web.HttpApplication
  
• Any modification made during application execution causes application restart
  

Contents/Syntax of Global.asax

• Four elements determine the syntax of the global.asax file
  

1. Application Directives
   
2. Code declaration blocks
   
3. Server side <object> tags
   
4. Server side includes
   

Application Directives

• The global.asax supports three directives: @Application, @Import and @Assembly
  
• @Import directive imports a namespace into an application
  
• @Assembly directive links an assembly to the application at compile time
  
• @Application supports a few attributes - Description, Language and Inherits
  

Code Declaration Blocks

• A global.asax file can contain code wrapped by a <script> tag
  
• <script language= "C#" runat="server" src="global.aspx.cs">
  

Server-Side <object> tags

• The server-side <object> tag allows to create new objects using a declarative syntax
  
• object tag can take three forms, depending on the specified type
  

  <object id="..." runat="server" scope=Pipeline|Application|Session class="...">
  

  <object id="..." runat="server" scope=Pipeline|Application|Session progid="...">
  

  <object id="..." runat="server" scope=Pipeline|Application|Session classid="...">
  

• In first case, the object is identified by the name of the class and assembly that contains it
  
• In other two cases, the object to create is a COM object identified by the progid or classid
  

Server-Side Includes

• An #include directives inserts the contents of the specified file as-is into the ASP.net file that uses it
  
• The directive must be enclosed in an HTML comment
  
• <!-- #include file="filename"> or <!-- #include virtual="filename">
  

Static Properties

• If static proerties are defined in global.asax file, they will be accessible for reading and writing by all pages in the application
  
• Sample code as under:
  

  <script language="C#" runat="server">
  

  public static int Counter = 0;
  

  </script>
  

• To access this property from a page, code as under
  

  Response.Write(ASP.global_asax.Counter.ToString());