使用這些事件的一個關鍵問題是知道它們被觸發的順序。application_init 和application_start 事件在應用程序第一次啟動時被觸發一次。相似地，application_disposed 和 application_end 事件在應用程序終止時被觸發一次。此外，基于會話的事件（session_start 和 session_end）只在用戶進入和離開站點時被使用。其余的事件則處理應用程序請求，這些事件被觸發的順序是：

·         application_beginrequest

·         application_authenticaterequest

·         application_authorizerequest

·         application_resolverequestcache

·         application_acquirerequeststate

·         application_prerequesthandlerexecute

·         application_presendrequestheaders

·         application_presendrequestcontent

·         <<執行代碼>>

·         application_postrequesthandlerexecute

·         application_releaserequeststate

·         application_updaterequestcache

·         application_endrequest

這些事件常被用于安全性方面。下面這個 c# 的例子演示了不同的global.asax 事件，該例使用application_authenticate 事件來完成通過 cookie 的基于表單（form）的身份驗證。此外，application_start 事件填充一個應用程序變量，而session_start 填充一個會話變量。application_error 事件顯示一個簡單的消息用以說明發生的錯誤。

protected void application_start(object sender, eventargs e) {
application["title"] = "builder.com sample";
}
protected void session_start(object sender, eventargs e) {
session["startvalue"] = 0;
}
protected void application_authenticaterequest(object sender, eventargs e) {
// extract the forms authentication cookie
string cookiename = formsauthentication.formscookiename;
httpcookie authcookie = context.request.cookies[cookiename];
if(null == authcookie) {
// there is no authentication cookie.
return;
}
formsauthenticationticket authticket = null;
try {
authticket = formsauthentication.decrypt(authcookie.value);
} catch(exception ex) {
// log exception details (omitted for simplicity)
return;
}
if (null == authticket) {
// cookie failed to decrypt.
return;
}
// when the ticket was created, the userdata property was assigned
// a pipe delimited string of role names.
string[2] roles
roles[0] = "one"
roles[1] = "two"
// create an identity object
formsidentity id = new formsidentity( authticket );
// this principal will flow throughout the request.
genericprincipal principal = new genericprincipal(id, roles);
// attach the new principal object to the current httpcontext object
context.user = principal;
}
protected void application_error(object sender, eventargs e) {
response.write("error encountered.");

這個例子只是很簡單地使用了一些global.asax 文件中的事件；重要的是要意識到這些事件是與整個應用程序相關的。這樣，所有放在其中的方法都會通過應用程序的代碼被提供，這就是它的名字為global 的原因。

這里是前面的例子相應的 vb.net 代碼：

sub application_start(byval sender as object, byval e as eventargs)
application("title") = "builder.com sample"
end sub
sub session_start(byval sender as object, byval e as eventargs)
session("startvalue") = 0
end sub
sub application_authenticaterequest(byval sender as object, byval e as
 eventargs)
' extract the forms authentication cookie
dim cookiename as string
cookiename = formsauthentication.formscookiename
dim authcookie as httpcookie
authcookie = context.request.cookies(cookiename)
if (authcookie is nothing) then
' there is no authentication cookie.
return
end if
dim authticket as formsauthenticationticket
authticket = nothing
try
authticket = formsauthentication.decrypt(authcookie.value)
catch ex as exception
' log exception details (omitted for simplicity)
return
end try
dim roles(2) as string
roles(0) = "one"
roles(1) = "two"
dim id as formsidentity
id = new formsidentity(authticket)
dim principal as genericprincipal
principal = new genericprincipal(id, roles)
' attach the new principal object to the current httpcontext object
context.user = principal
end sub
sub application_error(byval sender as object, byval e as eventargs)
response.write("error encountered.")
end sub

資源

global.asax 文件是 asp.net 應用程序的中心點。它提供無數的事件來處理不同的應用程序級任務，比如用戶身份驗證、應用程序啟動以及處理用戶會話等。你應該熟悉這個可選文件，這樣就可以構建出健壯的asp.net 應用程序。