README.md

Description

This tutorial shows how you can list the users authenticated in your site using session object.

More Info

Submitted On
By	dotnetme
Level	Intermediate
User Rating	4.2 (25 globes from 6 users)
Compatibility	VB.NET, ASP.NET
Category	Internet/ Browsers/ HTML
World	.Net (C#, VB.net)
Archive File

Source Code

Ok, here is a code snipet to determine who is online on your web site. Essentially there are 2 tables Users and OnlineUsers. I did it this way to not attach the sessionID field to each user (text about 20 chars long) and waste DB space.

the UserID can be autonumeric (PK) .

First of all, when a user log in, we insert a record on the OnlineUsers table. The values are the UsserID that loged in (duh) and the sessionID property of the Session Object.

Here is a code snippet: (for the login form, assuming you are using forms authentication)

Private Sub LoginButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LoginButton.Click
Response.cookies(“UserID”)=txtUsername.Text
Dim cnn as new oledb.oledbconnection(ConfigurationSettings.Appsettings(“cnnString”)
Dim strInsert as string = “Insert into OnlineUsers (UserID,SessionID) Values(‘ “ & txtUserName.Text & “’,’” & Session.SessionID & “’)”
Dim oldbInsert as new oledbCommand(strInsert,cnn)
Cnn.open()
OldbInsert.ExecuteNonQuery()
Dim strUpdate as string = “Update Users set Online = True where UserID =’“ & txtUserName.Text & “’”
Dim oldbUpdate as new oledbCommand(strUpdate,cnn)
OldbUpdate.ExecuteNonQuery()

End Sub

Now, when the users click logout somewhere in your page:

Private Sub LogoutButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LogoutButton.Click

Dim cnn as new oledb.oledbconnection(ConfigurationSettings.Appsettings(“cnnString”)
Dim strDelete as string = “Delete from OnlineUsers where SessionID =’” & Session.SessionID & “’”

Dim oldbDelete as new oledbCommand(strdelete,cnn)
Cnn.open()
OldbDelete.ExecuteNonQuery()


Dim strUpdate as string = “Update Users set Online = false where UserID =’“ & Response.cookies(“UserID”).value & “’”
Dim oldbUpdate as new oledbCommand(strUpdate,cnn)
OldbUpdate.ExecuteNonQuery()

End Sub

Now, what for am I using the session ID?

What happens if a user doesn’t press the logout button? It will be online until it hits the logout button.

So in your Session_End event. In your Global.asx.vb you can put this code so when the session expires, the app automatically deletes the record from the users table and put the online status = False.

Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)

Dim cnn As New
OleDb.OleDbConnection(ConfigurationSettings.AppSettings("ConnectionString") & ConfigurationSettings.AppSettings("DBPath"))
Dim strUserID As String = ""
Dim rdr As OleDb.OleDbDataReader
Dim com As New OleDb.OleDbCommand("Select UserID from OnlineUsers where SessionID ='" & Session.SessionID & "'", cnn)

cnn.Open()
rdr = com.ExecuteReader
While rdr.Read()
strUserID = CStr(rdr.GetValue(0))
End While
rdr.Close()
If strUserID <> "" Then
com.CommandText = "Delete from OnlineUsers where UserID =" & strUserID
com.ExecuteNonQuery()
com.CommandText = "Update Users Set Online = False where UserID =" & strUserID
com.ExecuteNonQuery()
End If

cnn.Close()
End Sub

Now you can present the users with the Online=true on a datagrid or other bound control =)
Note:
You cannot call subs or functions from the session_end events, or it will not execute.

Also When an error occurs you don’t get notified, even in debug, because this is executed in a background process.

So I hope you learn a little from this tut, I passed long hours to get to this =)

And a final note: sorry about my English, I’m from Mexico (heheh)

Vote!