How to prevent the same account repeated login system

How to prevent control of the client from repeat the login system with the same account.

Solution: Maintain an online table, check with logins, will not log in again, as a sessionID as a unique identifier symbol, can also generate a GUID to cookie, distinguish between different clients, then JS, can achieve better The effect, such as automatically offline the code after departure:

Public Virtual Void Application_Start (Object Sender, Eventargs E) {// Reset The Mailer IndicatorApplication ["Mailerstatus"] = "all mailings completion";

// initialize a datatable for users onlineDataTable objUserTable = new DataTable (); objUserTable.Columns.Add ( "SessionID", System.Type.GetType ( "System.Guid")); objUserTable.Columns.Add ( "PeopleID", System .Type.gettype ("system.int32"))); objusertable.columns.add ("ShowDetail", System.Type.GetType ("System.Boolean")); Datacolumn [] pk = new datacolumn [1]; pk [ 0] = Objusertable.columns [0]; objusertable.primarykey = pk; Application ["useertable"] = objusertable;} ///

/// The session_start event address us /// Application ["useertable"]. ///

Public Virtual Void Session_Start (Object Sender, Eventargs E)

{

Application.lock ();

//Application.lock ();

DataTable objusertable = (dataable) Application ["useertable"];

DataRow Objrow = Objusertable.newrow ();

Guid Objguid = guid.newguid ();

Objrow [0] = Objguid;

Session ["PFSessionID"] = Objrow [0];

Objrow [1] = 0;

Objrow [2] = false;

Objusertable.Rows.Add (objrow);

Application ["" "= objusertable;

Application.unlock ();

}

///

//////// Application ["useertable"]. ////////////

Public Virtual Void Session_end (Object Sender, Eventargs E) {

Application.lock ();

DataTable objusertable = (dataable) Application ["useertable"];

Objusertable.Rows.Find ((GUID) Session ["PfSessionID"]). delete ();

Application ["" "= objusertable;

Application.unlock ();

}