Tip: asp.net 2.0 prevents the same user from landing at the same time

Asp.net| Tips

To prevent the same user from landing at the same time, the home page should record the information of the online user (here with the user name for example), and then determine whether the user is logged in. Here, a cache is used to store the username that has been logged in, but there is a question of knowing when the user left the system. This is to periodically clear the contents of the cache, that is, set a cache time. This time can be associated with the user's session value, and the user's information in the cache is also emptied when the user sessions value is invalidated. This achieves the effect of preventing simultaneous landing, the specific code is as follows:

Place on the successful landing:

string key = TextBox1.Text; User name textbox set to cache keyword
String uer = Convert.ToString (Cache[key]); Read the user's corresponding value in the cache
To determine if there is a user's information in the cache, if there is no relevant value, indicating that the user did not log in
if (Uer = null | | uer = = String.Empty)
{
Define cache Expiration Time

TimeSpan sesstimeout = new TimeSpan (0, 0, System.Web.HttpContext.Current.Session.Timeout, 0, 0);

Insert a user-related cache value on the first landing
HttpContext.Current.Cache.Insert (key, key, NULL, DateTime.MaxValue, Sesstimeout, System.Web.Caching.CacheItemPriority.NotRemovable, NULL);
session["Adminid"] = TextBox1.Text;
Response.Redirect ("main.aspx");
}
Else
{
Repeat Login
Response.Write (' Your account has landed! ') ("<script>alert"); window.location= ' login.aspx ';</script> ");
}