The core task of a counter is to record the number of visits and read data records conveniently. The hosts file is used to store access records, including global. asax and Global. asax. cs. These two files are core files and are mainly responsible for responding to events and reading and writing files. Therefore, a program must have functions such as opening a file, reading a file, accumulating a number, and writing a file. At the same time, you should also note that when adding a value, it cannot be written as in ASP.
Application ("counter") = Application ("counter") + 1
Because the numeric type cannot perform mathematical operations with the object. After thinking above, we can basically write code, but before writing, we should also understand the following knowledge.
Related Knowledge
1. Global. asax File
The global. asax file is also called an ASP. NET application file, which is usually stored in the root directory. The code in this file does not generate a user interface or correspond to a single page request. It is mainly responsible for processing application_start, application_end, session_start and session_end events.
2. Application object and its events
The application object comes from the httpapplictionstat class. It can share public information between multiple requests and connections, or act as an information transmission pipeline between request connections. The life cycle of this object starts when IIS starts to run and when someone starts to connect, it ends when IIS is closed or no one is connected for several times (20 minutes by default ). When the life cycle of the Application object starts, the application_start event is started. When the life cycle of the Application object ends, the application_end event is started.
3. Session objects and events
Session objects have similar events as application: session_start and session_end events. When a new user accesses the application, the session_start event is triggered immediately. When a user stops access or the program executes the session. Abandon method, the session_end event is triggered.
4. Comparison of application and session objects
The Session object is somewhat similar to the application object, but its scope is limited. The application object is effective for all users, while the session object is opposite. each user has its own session object. its lifecycle starts from the server's response to the user request page, it is terminated when the user disconnects from the server. The application object does not trigger an event when a new user request is like a session object. The application object event is only triggered once, that is, the first request of the first user. An application_end event must occur after the session_end event. The application_end event is triggered only when the server stops working or the application_end event is uninstalled.
Procedure
First, create a counter.txt file. open the file and enter an integer greater than 0 as the initial value of the access record.
We can officially compile the counter program.
Listing 1 is webform1.aspx, which is mainly used to display records of the number of accesses read from the file. Because the application object is valid throughout the application lifecycle, it can be accessed on different pages, just as convenient as using global variables.
In the code, <% = application ["counter"] %> is used to indicate the number of visits.
The program code is as follows:
Listing1 ----- webform1.aspx -----
<% @ Page Language = "C #" src = "webform1.aspx. cs" inherits = "counter1.webform1" %>
<! Doctype HTML public "-// W3C // dtd html 4.0 transitional // en">
<HTML>
<Head>
<Meta name = "generator" content = "Microsoft Visual Studio 7.0">
<Meta name = "code_language" content = "C #">
</Head>
<Body>
<Form ID = "form1" method = "Post" runat = "server">
<Font face = ""> you are the <% = application ["counter"] %> visitor! </Font>
</Form>
</Body>
</Html>
Listing 2 and listing3 are the code of the global. asax and Global. asax. CS files. They are executed before the webform1.aspx files are executed. Some events and response code are defined in the Global. asax. CS file, which is mainly used to read and write files and accumulate values.
Listing 2 ----- global. asax ----
<% @ Application src = "Global. asax. cs" inherits = "counter2.global" %>
Listing 3 ----- global. asax. CS -----
Using system;
Using system. collections;
Using system. componentmodel;
Using system. Web;
Using system. Web. sessionstate;
Using system. IO;
Namespace counter2
{
Public class Global: system. Web. httpapplication
{
Protected void application_start (Object sender, eventargs E)
{
Uint COUNT = 0;
Streamreader SRD;
// Obtain the actual path of the file
String file_path = server. mappath ("counter.txt ");
// Open the file for reading
SRD = file. opentext (file_path );
While (SRD. Peek ()! =-1)
{
String STR = SRD. Readline ();
Count = uint32.parse (STR );
}
Object OBJ = count;
Application ["counter"] = OBJ;
SRD. Close ();
}
Protected void session_start (Object sender, eventargs E)
{
Application. Lock ();
// Value accumulation. Note that boxing is used here)
Uint jishu = 0;
Jishu = (uint) application ["counter"];
Jishu = jishu + 1;
Object OBJ = jishu;
Application ["counter"] = OBJ;
// Write data records to files
String file_path = server. mappath ("counter.txt ");
Streamwriter FS = new streamwriter (file_path, false );
FS. writeline (jishu );
FS. Close ();
Application. Unlock ();
}
Protected void application_beginrequest (Object sender, eventargs E)
{
}
Protected void application_endrequest (Object sender, eventargs E)
{
}
Protected void session_end (Object sender, eventargs E)
{
}
Protected void application_end (Object sender, eventargs E)
{
// Packing
Uint JS = 0;
JS = (uint) application ["counter"];
// Object OBJ = JS;
// Application ["counter"] = JS;
// Write data records to files
String file_path = server. mappath ("counter.txt ");
Streamwriter FS = new streamwriter (file_path, false );
FS. writeline (JS );
FS. Close ();
}
}
}
After the above discussion, a simple homepage counter is complete. Its core is to read and write files in text mode.
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