Asp. NET Web site management system exit clear browser cache, session code _ Practical skills

1, in the system Landing Success Record login username, password and other information (login function part of the code)

Copy Code code as follows:

session["id"] = user.id.ToString ();
session["name"] = User.name.ToString ();
session["pwd"] = user.password.ToString ();
session["Time" = user. Logintime.tostring ();
session["authority"] = user.limits.ToString ();

2. Add the following code to each page of the management system to determine whether the session value is empty when the page is loaded

Copy Code code as follows:

protected void Page_Load (object sender, EventArgs e)
{
if (session["id"] = = NULL | | session["name"] = = NULL | | session["time"] = = NULL | | session["authority"] = = NULL | | session["pwd"] = = null)
Response.Redirect ("~/login.aspx", true);
if (! IsPostBack)
{
。。。。。。
}
}

3, in the Click "Exit System" execution of the event to add the session empty code and browser cache empty code

Copy Code code as follows:

public void clear (object sender, EventArgs e)
{
session["id" = NULL;
session["name" = null;
Clearclientpagecache ();
Response.Redirect ("~/login.aspx");
}
public void Clearclientpagecache ()
{
Clear browser Cache
Response.Buffer = true;
Response.ExpiresAbsolute = DateTime.Now.AddDays (-1);
Response.Cache.SetExpires (DateTime.Now.AddDays (-1));
Response.Expires = 0;
Response.CacheControl = "No-cache";
Response.Cache.SetNoStore ();
}

Because my "Exit system" is written in the master page with HTML <a> tags, the above code is written in the. cs file of the master page.
Master Page code:

Copy Code code as follows:

<a class= "atop" target= "_self" <span style= "Background-color: #ff0000" >runat= "Server" onserverclick</ span> = "Clear" > Exit system </a>

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The previous version has been unable to achieve the function, tangled for a long time, did not find out the problem, the just started to carry out the wrong code posted, but also I think the wrong place to paste out, I hope everyone criticized correct.
This version of the error is: Landing after the successful entry to the main page, and then click into other pages can not enter, will jump to the landing interface.
My thoughts:
1, I found in the track debugging, every time the page load will automatically execute the master page. cs file Clear () method, so you can not through other pages Page_Load () method of the IF (session["id"] = NULL | | session["name"] = = NULL | | session["time"] = = NULL | | session["authority"] = = NULL | | session["pwd"] = = null) Response.Redirect ("~/login.aspx", true);
2, my question is that the clear () method is clearly clicked before the execution, why every time the page load automatically executed?
3, I consider the cause of the error is the client and server-side implementation of the different methods, and then found on the internet on the onclick, and onserverclick differences, but their understanding is not very clear. I hope you can communicate.
The difference between onclick and OnServerClick see also: http://www.jb51.net/article/30313.htm
The front desk code is the first (master page foreground code):

Copy Code code as follows:

<a href= "~/login.aspx" class= "atop" target= "_self" onclick= "Clear ()" > Account information </a>
<script>
function Clear () <BR> {<br> <%clear ();%><br>}
</script>

Master Page Background Code

Copy Code code as follows:

public void Clear ()
{
session["id" = NULL;
session["name" = null;
}