I have written a basic asp classic class that handles all connections to our database.
when called everything works fine the first time but the second time it is called the recordset does not open any ideas?
Class SQLConnection
Private Sub Class_Initialize
set ConnectionObject = Server.CreateObject("ADODB.Connection")
Set RecordsetObject = Server.CreateObject("ADODB.Recordset")
End Sub
Private Sub Class_Terminate
Set ConnectionObject = Nothing
Set RecordsetObject = Nothing
End Sub
Public Default Property Get Item(sString)
On Error Resume Next
Item = RecordsetObject(sString)
On Error GoTo 0
If Err.Number <> 0 then
Item = null
End if
End Property
Public Sub MoveNext
If Not RecordsetObject.EOF Then RecordsetObject.MoveNext
End Sub
Public Function EOF
EOF = RecordsetObject.EOF
End Function
Public Sub Open(SQLStr,ConnStr)
ConnectionObject.Open ConnStr
RecordsetObject.Open SQLStr, ConnectionObject, 3
End Sub
Public Sub Close
RecordsetObject.Close
ConnectionObject.Close
End Sub
End Class
Set SQLConn = New SQLConnection
SQLConn.Open "SELECT top 10 id FROM tblProfileVillages", ConnectionString
Do While Not SQLConn.EOF
Response.write(SQLConn("id"))
SQLConn.MoveNext
Loop
SQLConn.Close
Set SQLConn = nothing
I think the error is in the Item property, you will have to check the err.Number before calling on error goto 0.
Use it like this:
Public Default Property Get Item(sString)
On Error Resume Next
Item = RecordsetObject(sString)
If Err.Number <> 0 then
Item = null
End if
On Error GoTo 0
End Property
Also I haven't seen "null" in vbScript yet. Is that a constant you made, or could it be that you are missing an error somewhere?
The on error goto next business can be annoying sometimes. :)
It turns out if your sql statement can't be displayed in a grid then the object closes instantly like say an insert statement.
I solved this by checking if the object is open before running code with If RecordsetObject.State = 1 then
Related
I am trying to spawn a new thread from an ASP page written in VB.NET, on .NET 3.5.
The page allows a user to upload files and then processes the files into the database.
As the processing can take a while, I want to upload them, spawn the processing onto a new thread, and then when it completes send the user a notification through our database-driven notification module in the system.
I've tried a couple different examples I've found online, but they don't seem to work. There is no error thrown, but it never seems to actually launch the processing code on a new thread either.
Here is my submittal code in the web page:
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
Try
If Not (file1.HasFile Or file2.HasFile Or file3.HasFile Or file4.HasFile Or file5.HasFile) Then
AddErrorMessage("Please specify at least one file.")
Else
Dim l = New List(Of InventoryUploads.File)
If file1.HasFile Then l.Add(New InventoryUploads.File With {.Name = file1.FileName, .Content = file1.FileContent})
If file2.HasFile Then l.Add(New InventoryUploads.File With {.Name = file2.FileName, .Content = file2.FileContent})
If file3.HasFile Then l.Add(New InventoryUploads.File With {.Name = file3.FileName, .Content = file3.FileContent})
If file4.HasFile Then l.Add(New InventoryUploads.File With {.Name = file4.FileName, .Content = file4.FileContent})
If file5.HasFile Then l.Add(New InventoryUploads.File With {.Name = file5.FileName, .Content = file5.FileContent})
InventoryUploads.ProcessFiles(l, Session.UserIdent, chkRcvOverwrite.Checked)
NewRow("Your files have been queued and are being processed. You will be sent a notification when they are completed.")
End If
Catch ex As Exception
LogEx(ex)
NewRow("There was an error queueing your files." & BR & ex.Message)
End Try
End Sub
From a UI point of view, this all works, the page posts the files, and it shows the user the message about "your files have been queued".
The call to InventoryUploads.ProcessFiles is an encapsulation function in front of the threading code, which is all contained in the InventoryUploads module (following):
Imports System.Threading
Imports System.Threading.Tasks
Public Module InventoryUploads
Public Structure File
Private pName As String
Private pContent As IO.Stream
Private pProcessed As Boolean
Public Property Name As String
Get
Return pName
End Get
Set(value As String)
pName = value
End Set
End Property
Public Property Content As IO.Stream
Get
Return pContent
End Get
Set(value As IO.Stream)
pContent = value
End Set
End Property
Public Property Processed As Boolean
Get
Return pProcessed
End Get
Set(value As Boolean)
pProcessed = value
End Set
End Property
End Structure
Public Sub ProcessFiles(files As List(Of File), userident As String, receivingsOverwrite As Boolean)
Try
Dim params = Array.CreateInstance(GetType(Object), 3)
params(0) = files
params(1) = userident
params(2) = receivingsOverwrite
'// Threading Method 1
Dim pts = New ParameterizedThreadStart(AddressOf ThreadedProcessFiles)
Dim thd = New Thread(pts)
thd.IsBackground = True
thd.Start(params)
'// Threading Method 2
'ThreadPool.QueueUserWorkItem(AddressOf ThreadedProcessFiles, params)
'// Threading Method 3
Dim f As Func(Of Integer) = Function() ThreadedProcessFiles(params)
Task.Factory.StartNew(f)
Catch ex As Exception
IO.File.WriteAllText("C:\idwherenet.log", ex.Message)
Throw
End Try
End Sub
''' <summary>
'''
''' </summary>
''' <param name="params">exepcts params to contain 3 objects,
''' 1) type List(Of File),
''' 2) string userident to notify on finish
''' 3) boolean whether receivings should overwrite</param>
''' <remarks></remarks>
Private Function ThreadedProcessFiles(params() As Object) As Boolean
IO.File.WriteAllText("C:\mylog.log", "hello ThreadedProcessFiles?")
'Log("threadedprocessfiles: got here")
Dim files As List(Of File), uident As String = "", rcvovr As Boolean
Try
files = params(0)
uident = CStr(params(1))
rcvovr = CBool(params(2))
If files.Count = 0 Then
SendNotification(NotificationTypes.SYS, uident, "No files provided for inventory upload; nothing processed.")
Exit Sub
End If
For Each f In files
f.Processed = False
If f.Content.Length = 0 Then Continue For
'// process the file here....
f.Processed = True
Next
SendNotification(NotificationTypes.SYS, uident, "Inventory upload processing completed.")
Return True
Catch ex As Exception
'LogEx(ex)
'Log(ex.Message, ex.ToString)
If Not uident.IsEmpty Then SendNotification(NotificationTypes.SYS, uident, "Inventory upload processing encountered an error. " & ex.Message, ex.ToString)
Return False
End Try
End Sub
End Module
In the ProcessFiles sub, you can see the three different methods I have tried to spawn the thread, including a NuGet backport of the Task Parallel Library... neither works. I have confirmed that is is making it into the ProcessFiles sub, and the code to spawn the thread is not throwing any errors... it just never actually calls the ThreadedProcessFiles function.
Any ideas?
UPDATE: Oh, actually, the NuGet package DOES seem to be working, FINALLY! It just doesn't write out to the file (context/security/impersonation permissions I guess). Now I can finally move on!
If you're using .NET 4 or 4.5, the Task Parallel Library makes this sort of thing super easy:
Task.Factory.StartNew(Function() ThreadedProcessFiles(params));
(I think that's the right syntax for VB)
If you go this route, I would change the params to just send the three parameters separately.
Morning All,
I am using VS2010 with VB and im trying to get a ping test working in my web application. In order to do this and test that it works i have simply created a button that when clicks should ping a specified IP address.
I believe that the code for the button should work fine. The only issue i have is the following error message on my web page...
System.NullReferenceException: Object reference not set to an instance of an object.
It bugs on the cole line...
Console.WriteLine("Address: {0}", vPingReply.Address)
I thought that this was due to 'Properties' needing to be set up for the .Address and .Status objects. Im not too sure if i have added these correctly as i have added some properties but i still have the same issue when i run the page?
Can someone please take a look and advise?
Here is my full code...
Imports Microsoft.VisualBasic
Imports System.Text
Imports System.Net.NetworkInformation
Imports System.Net.NetworkInformation.PingReply
Partial Class Ping
Inherits System.Web.UI.Page
Private mSend As PingReply
Private Property Send(p1 As String) As PingReply
Get
Return mSend
End Get
Set(value As PingReply)
mSend = value
End Set
End Property
Private mAddress As PingReply
Private Property Address(p2 As String) As PingReply
Get
Return mAddress
End Get
Set(value As PingReply)
mAddress = value
End Set
End Property
Private mStatus As PingReply
Private Property Status(p3 As String) As PingReply
Get
Return mStatus
End Get
Set(value As PingReply)
mStatus = value
End Set
End Property
Protected Sub btnPing_Click(sender As Object, e As System.EventArgs) Handles btnPing.Click
Dim vPing As New Ping
Dim vPingReply As PingReply = vPing.Send("xxx.xx.xxx.xx")
Console.WriteLine("Address: {0}", vPingReply.Address)
Console.WriteLine("Status: {0}", vPingReply.Status)
End Sub
End Class
Any help is much appriechiated.
Betty.
You cannot access the content of Address property if the Status is not Success
Dim vPing As New Ping
Dim vPingReply As PingReply = vPing.Send("xxx.xx.xxx.xx")
if vPingReply.Status = IPStatus.Success Then
Console.WriteLine("Address: {0}", vPingReply.Address)
End If
Console.WriteLine("Status: {0}", vPingReply.Status)
The docs says
If the value of Status is not Success, you should not use the values
returned by the RoundtripTime, Options or Buffer properties. The
RoundtripTime property will return zero, the Buffer property will
return an empty array, and the Options property will return null.
but I found that the Address property is null (Nothing in VB) also if the Send is for a non-existant ip address or DNS name
However, looking better at your code, it is clear that all the calls made inside the btnPing_Click method are handled by your class Ping not to the framework class Ping. And your class uses variables not correctly initialized. I suggest to remove those methods from your class or just rename the class with something different.
Another option (not recommended) is this
Private Property Send(p1 As String) As PingReply
Get
' Specify the full namespace to remove ambiguity between this class and framework class
Dim p = new System.Net.NetworkInformation.Ping()
mSend = p.Send(p1)
Return mSend
End Get
Set(value As PingReply)
mSend = value
End Set
End Property
Private Property Address() As String
Get
if mSend IsNot Nothing Then
Return mSend.Address
else
Return string.Empty
End If
End Get
' Meaningless ???
'Set(value As PingReply)
' mAddress = value
'End Set
End Property
Private mStatus As PingReply
Private Property Status() As String
Get
if mSend IsNot Nothing Then
Return mSend.Status.ToString()
else
Return string.Empty
End If
End Get
' Meaningless ???
'Set(value As PingReply)
' mStatus = value
'End Set
End Property
I am supporting some classic ASP pages, one of which uses and re-uses an object conn and disposes of it either when the .asp page finishes processing or right before the page redirects to another page.
<%
dim conn
...
set conn = server.CreateObject("adodb.connection")
...
sub cleanUp()
conn.Close
set conn = nothing
end sub
...
sub pageRedirect(url)
call cleanUp()
response.Redirect url : response.End
end sub
...
' very end of file
call cleanUp()%>
I've found that if there is a redirect, I get a server error right at the line conn.Close, Microsoft VBScript runtime error '800a01a8' Object required. I figure there's no reason why that line would execute more than once but to be safe I rewrote the function
sub cleanUp()
if(not (conn Is Nothing)) then
conn.Close
set conn = Nothing
end if
end sub
But I still get that exact error, now at the line if(not (conn Is Nothing))!! I thought the purpose of Is Nothing was to do a test before using the variable name conn precisely to prevent that 'object required' error, but the test is throwing the same error.
What other test can I use to make sure conn isn't referenced if it'd already been set to Nothing?
is nothing is used to test for an object reference, if the variable does not contain such then the test is invalid & raises an error, so conn can only be tested after its been set to something.
You can;
if isobject(conn) then
if not (conn Is Nothing) then set conn = nothing
end if
Use option explicit (each time a script runs without option explicit, a puppie dies out there), you probably would have detected the problem earlier as Nilpo mentioned.
When you dim a variable that you are going to use as an object reference and test it on Nothing, make it a habbit to set it to Nothing at initialization time(*): dim myObject : Set myObject = Nothing.
(*) Not really at initialization, because the dim's are handled before a routine starts, but when you put all your dim's at the top of a routine, it will practically be the same.
Use the IsNothing function. You should also check that it is an object.
sub cleanUp()
if Not IsNothing(conn) then
if IsObject(conn) then
conn.Close
end if
set conn = nothing
end if
end sub
That being said, I would do it like this since setting a variable to nothing does no harm.
sub cleanUp()
if IsObject(conn) then
conn.Close
end if
set conn = nothing
end sub
More importantly though, your problem is that conn is not in scope for your subroutine. You should probably pass it in as a parameter.
I have the below mentioned code in a seperate class file for establishing connection and carry out DB transactions. I have an issue where multiple connections being opened which sometime exceed the connection pool. When I stepped through the code I found that there are codes which call ConnectDB() in a loop without calling DisconnectDB(). But I expected that the condition OraConn.State = ConnectionState.Closed should handle the situation. Somehow the condition is always satisfied hence openning another set of connection. Can you suggest where am I going wrong and also what best practice can be adopted here?
Public Class Connection
Dim Str_conn As String = "Data Source=...; User=...; password=...; Min Pool Size=10; Max Pool Size=500;"
Public OraConn As OracleConnection
Dim cmd As OracleCommand
Dim dr As OracleDataReader
Dim data_adapt As OracleDataAdapter
Dim dt As DataTable
Dim ds As DataSet
Public Sub ConnectDB()
OraConn = New OracleConnection(Str_conn)
If OraConn.State = ConnectionState.Closed Then
OraConn.Open()
End If
End Sub
Public Sub DisconnectDB()
If OraConn.State = ConnectionState.Open Then
OraConn.Close()
End If
End Sub
Public Function get_dataset(ByVal query As String, ByRef ds As DataSet) As DataSet
data_adapt = New OracleDataAdapter(query, OraConn)
data_adapt.Fill(ds)
Return ds
End Function
Public Function get_datareader(ByVal query As String) As OracleDataReader
cmd = New OracleCommand(query, OraConn)
dr = cmd.ExecuteReader()
Return dr
End Function
Public Sub UpdateDB(ByVal query As String)
cmd = New OracleCommand(query, OraConn)
cmd.ExecuteNonQuery()
cmd.Dispose()
End Sub
The class is refered in other classes or directly in the aspx.vb pages like this.
Public Function InsertData(ByVal var1 As String, ByVal var2 As String) As Integer
conn.ConnectDB()
Dim qryInsert As String
qryInsert = " INSERT INTO TABLE VALUES ('" & var1 & "', "
qryInsert = qryInsert & var2 & "')"
Try
conn.UpdateDB(qryInsert)
Catch ex As OracleException
If ex.Code = 1 Then
updData(var1, var2)
ElseIf ex.Code = 2091 Then
msgprompt("Duplicate Unique Key!", "Warning")
End If
Finally
conn.DisconnectDB()
End Try
Return count
End Function
The connection is again opened in function updData(). While I understand that it has to be closed correctly but keeping tab on every developer is not possible. Hence I want to control it directly from the connection class by using the same connection but the condition If OraConn.State = ConnectionState.Closed is not helping.
UPDATE
I have put the code in UpdateDB under a Using block and removed call to ConnectDB and DisconnectDB from function like InsertData(...). It seems that the issue has been resolved. But I would like to know in case of exception will the connection remain open? and also OraConn is a public variable defined outside Using block so will it be disposed of by the GC?
Public Sub UpdateDB(ByVal query As String)
Using OraConn = New OracleConnection(Str_conn)
cmd = New OracleCommand(query, OraConn)
Try
OraConn.Open()
cmd.ExecuteNonQuery()
Catch ex As Exception
Throw
Finally
cmd.Dispose()
End Try
End Using
End Sub
You must close all the connections as soon as you are done with it, no matter what.
Suggestion:
The best practice for closing the connection is to do it in finally block. So that even if there is any error, catch it (log it if required) in catch block, and then connection will get close in finally block.
UPDATE
You can put one private static counter in your Connection class. When ever ConnectDB() is called you increment this counter and decrement it in every DisconnectDB(). Now in ConnectDB() you check the value of counter, if it exceeds a minimum threshold you throw error, by doing this way; you can come to know idle connection present in your code and refactor it. On production keep this threshold value high or ignore it in code.
i have some test code which i run at every load of a page in my asp.net website
this is the code
Sub TryThreads()
Dim t1 = New Thread(AddressOf TryLock)
t1.Priority = ThreadPriority.Lowest
t1.Start()
Dim t2 = New Thread(AddressOf TryLock)
t2.Priority = ThreadPriority.Lowest
t2.Start()
End Sub
Sub TryLock()
Dim LockObject = New Object
SyncLock LockObject
DoTrace("entered locker")
For x = 0 To 10000
Next
DoTrace("exiting locker")
End SyncLock
DoTrace("exited locker")
End Sub
the "dotrace" simply add a record to a log table in the db
now the right result would be that i should have the entries in the db in order "entered","exiting","exited"
but actually when i look in the db i see first 2 "entered" then 2 "exiting" etc.
meaning that the multithreading is working ok, but not the synclock
is that correct?
and how can this be fixed?
the real code will be adding records to the db and might be called from several pages of different sessions, but the same code must not run twice concurrently
i do appreciate anybodys help
thank you very much!!!
EDIT:
in response to Sashas wonderful post i changed my code to a class (it was in a module) and now it looks like this:
Public Class CheckClass
Property LockObject As Object
Get
If HttpRuntime.Cache("CheckSessionsLock") Is Nothing Then HttpRuntime.Cache("CheckSessionsLock") = New Object
Return HttpRuntime.Cache("CheckSessionsLock")
End Get
Set(ByVal value As Object)
If value Is Nothing Then
HttpRuntime.Cache.Remove("CheckSessionsLock")
Else
HttpRuntime.Cache("CheckSessionsLock") = value
End If
End Set
End Property
Sub TryThreads()
Dim t1 = New Thread(AddressOf TryLock)
t1.Priority = ThreadPriority.Lowest
t1.Start()
Dim t2 = New Thread(AddressOf TryLock)
t2.Priority = ThreadPriority.Lowest
t2.Start()
End Sub
Sub TryLock()
SyncLock LockObject
DoTrace("entered locker")
For x = 0 To 10000
Next
DoTrace("exiting locker")
End SyncLock
DoTrace("exited locker")
End Sub
End Class
now it works 80-90% of the time.
on page load i have:
Dim cc = New CheckClass
cc.TryThreads()
if i open multiple pages at once, they still clash some times. but if i'm correct, the issue is now not with the synclock as much as with the httpruntime.cache, because when using a standard property, on one page, the code works 100%.
so how can i make sure that 2 threads, even from totally different sessions never run the trylock simultaneously?
thank you all for helping out
You are creating a new object instance when the TryLock method is called, and use that for locking. If you want mutual exclusion between the two threads, you need to use a common object instance for locking, e.g. a static member of your class or a parameter that you pass to both threads.