Please have a look at the code below, which I have written as a test. It does not make the ASP.NET process grow too much:
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Try
Dim Test As Integer
For Test = 0 To 1000000
Test1()
Next
Dim Test2 As String = "Test"
Catch ex As Exception
End Try
End Sub
Public Sub Test1()
Try
Dim objCommand As New SqlCommand
Dim strConString As String = "Data Source=IANSCOMPUTER;Initial Catalog=Test;Integrated Security=True"
Dim objCon As New SqlConnection
objCon.ConnectionString = strConString
objCon.Open()
objCommand.Connection = objCon
objCommand.CommandText = "select * from person "
Dim objDR As SqlDataReader = objCommand.ExecuteReader
If objDR.HasRows Then
Using objCon
End Using
End If
Catch ex As Exception
'I don't swallow exceptions.
End Try
End Sub
End Class
I am trying to detect a memory leak. I have found code similar to the above in the affected project. I notice that objCommand.dispose is not called. The project in question connects to an Oracle database and an SQL database. When connecting to an SQL database the above code is used. When connecting to an Oracle database Oracle.dataaccess.dll is used and the code looks different to reflect this.
My specific question is: if I avoid calling sqlcommand.dispose then will this cause a memory leak over time?
If a class has a Dispose method, that isn't getting called, then it is likely to be the source of a memory leak. Use Using, and it will call the Dispose method for you.
Your second example should look like the below, where all disposable object are wrapped in using blocks.
Dim strConString As String = "Data Source=IANSCOMPUTER;" +
"Initial Catalog=Test;Integrated Security=True"
Dim sqlStr as String = "select * from person "
Using objCon As New SqlConnection(strConString)
Using objCommand As New SqlCommand(sqlStr, objCon)
objCon.Open()
Using objDR As SqlDataReader = objCommand.ExecuteReader
If objDR.HasRows Then
End If
End Using
End Using
End Using
Related
My new application page is getting a timeout error every hour or so after getting some traffic on the page, and by traffic I mean users submitting 5-10 applications. How do I find the cause of the connections getting tied up?
This has been an issue in the past so whenever I use a sql data reader object I make sure to implement the "Using" statement. I've also made sure that the thread isn't aborted before the data reader is disposed of. I doubt that my use of data readers is the issue, so maybe it's my non-query code that's causing the issue, but I can't see why.
I also use a few sqldatasource objects for my dropdownlist controls, and as far as I know it wouldn't be the source of my issue.
See code example for how I use my sql objects.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Using drApp As SqlDataReader = LookupAppByID()
'some code
drApp.Close()
End Using
End Sub
Public Function LookupAppByID() As SqlDataReader
Dim Command As New SqlClient.SqlCommand
Command.Connection = GetDBConnection()
Command.CommandType = CommandType.Text
Command.CommandText = "select statement"
Return Command.ExecuteReader(CommandBehavior.CloseConnection)
End Function
Public Function UpdateAppStatus() As Integer
UpdateAppStatus = 0
Using Command As New SqlClient.SqlCommand("update statement", GetDBConnection())
UpdateAppStatus = Command.ExecuteNonQuery()
Command.Connection.Close()
Command.Connection.Dispose()
Command.Dispose()
End Using
End Function
Public Function GetDBConnection() As SqlClient.SqlConnection
Dim connection As New SqlClient.SqlConnection
connection.ConnectionString = "connection string"
connection.Open()
Return connection
End Function
Obviously I expect it to chug along without a hitch but when users start hitting the page it gets this error: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
Is there a problem with my code?
How can I narrow down what is causing this issue?
I would keep the database objects local so I can ensure that they are closed and disposed. Create and dispose within one method. I created a class so you can easily pass all its properties in a single variable.
'User Interface Code
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Dim id As Integer 'No sure where the value comes from
Using dtApp As DataTable = DataAccess.LookupAppByID(id)
'some code
End Using
End Sub
Protected Sub Update_Click(sender As Object, e As EventArgs) Handles Update.Click
Dim Applic As New ApplicationData()
Applic.ApplicantsName = txtName.Text
Applic.ID = CInt(txtID.Tex)
Applic.ApplicationStatus = "Approved"
Dim retVal = DataAccess.UpdateAppStatus(Applic)
If retVal = 1 Then
'Alert user of success
Else
'Alert user of failure
End If
End Sub
Public Class ApplicationData
Public Property ID As Integer
Public Property AppDate As Date
Public Property ApplicantsName As String
Public Property ApplicationStatus As String
End Class
Public Class DataAccess
Private Shared ConString As String = "Your connection string"
Public Shared Function LookupAppByID(AppID As Integer) As DataTable
Dim dt As New DataTable
Using cn As New SqlConnection(ConString)
Using Command As New SqlCommand("select * From YourTable Where ID = #ID", cn)
Command.Parameters.Add("#ID", SqlDbType.Int).Value = AppID
cn.Open()
dt.Load(Command.ExecuteReader)
End Using
End Using
Return dt
End Function
Public Shared Function UpdateAppStatus(App As ApplicationData) As Integer
Dim AppStatus = 0
Using cn As New SqlConnection(ConString)
Using Command As New SqlClient.SqlCommand("Update YourTable Set Status = #Status Where ID = #ID;", cn)
Command.Parameters.Add("#Status", SqlDbType.VarChar, 50).Value = App.ApplicationStatus
Command.Parameters.Add("#ID", SqlDbType.Int).Value = App.ID
cn.Open()
AppStatus = Command.ExecuteNonQuery()
End Using
End Using
Return AppStatus
End Function
End Class
I am having a library system database. I want to include a search box where I can search for a book name. I am using sql server. I know how to write a sql statement using the LIKE %''% clause, but the thing is I am writing this sql statement in a separate file and include that in the sub method in vb.net. How can I make that statement use the text entered in textbox?
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim str As String = ("Data Source=.\INSTANCE;initial catalog=example;user=sa;password=gariahat")
Dim con As New SqlConnection(str)
Dim cmd As New SqlCommand("select * from item where book_id like '%" + Trim(TextBox1.Text) + "%'", con)
Dim da As New SqlDataAdapter(cmd)
Dim ds As New DataSet()
If (da.Fill(ds, "item")) Then
ItemDataGridView.DataSource = ds.Tables(0)
MessageBox.Show("match found")
Else
MessageBox.Show("match not found")
End If
End Sub
I know this sub will work if I include the sql statement in the sub itself. But I use squaler to store my sql stored procedures and use those file in my sub, that file does not accept 'textbox.text'.
Example:
Public Shared Sub AccountDeposit(ByVal value As Integer, ByVal AccountNumber As String, ByVal connection As SqlConnection)
Dim cmd As New SqlCommand("AccountDeposit", connection)
cmd.CommandType = Data.CommandType.StoredProcedure
cmd.Parameters.AddWithValue("#AccountNumber", AccountNumber)
cmd.Parameters.AddWithValue("#Value", value)
cmd.ExecuteNonQuery()
End Sub
Here "AccountDeposit" is my stored procedure which i included in my sub.I want to do similar thing here but dont know how to include the text in textbox to sql statement
How can I execute a stored procedure on OnClick button with no parameters? I have the following code behind:
Protected Sub btnExport_Click(sender As Object, e As System.EventArgs) Handles btnExport.Click
Dim exec As SqlCommand = New SqlCommand("up_ExportFile", conn)
exec.CommandType = CommandType.StoredProcedure
End Sub
Supposing you have already opened the connection just add the ExecuteNonQuery method
Protected Sub btnExport_Click(sender As Object, e As System.EventArgs) Handles btnExport.Click
Dim exec As SqlCommand = New SqlCommand("up_ExportFile", conn)
exec.CommandType = CommandType.StoredProcedure
exec.ExecuteNonQuery()
End Sub
However I suggest you to not keep a global variable holding your SqlConnection opened for the lifetime of your application. Remember that the ADO.NET provider for SqlServer implements the connection pooling mechanism and thus, opening a connection is a lightweight procedure.
So a better approach is
Using conn = new SqlConnection("your_connection_string_here")
conn.Open()
Dim exec As SqlCommand = New SqlCommand("up_ExportFile", conn)
exec.CommandType = CommandType.StoredProcedure
exec.ExecuteNonQuery()
End Using
In this way the connection object is created just when needed, and then closed and disposed
See Using Statememt
Please help! I'm still learning so this might be completely wrong. I have built a multi-user web application for internal purposes. I have split my code up to make it more manageable and have run into some problems. I suspect that I have done something very silly!
I have a class in a separate file (quoteStatus.vb) in App_Code here it is:
Imports Microsoft.VisualBasic
Imports System.Data.SqlClient
Imports System.Data
Public Class quoteStatusHelper
Public Shared QuoteStatus As String
Public Shared Sub GetQuoteStatus(ByVal QuoteID As String)
Dim con As New SqlConnection
Dim cmd As New SqlCommand
Try
con.ConnectionString = ConfigurationManager.AppSettings("quotingSystemConnectionString")
con.Open()
cmd.Connection = con
cmd.CommandText = "SELECT Status FROM Quote WHERE QuoteID =" & QuoteID & ";"
Dim lrd As SqlDataReader = cmd.ExecuteReader()
While lrd.Read()
QuoteStatus = lrd("Status")
End While
Catch ex As Exception
Finally
con.Close()
End Try
End Sub
End Class
I use this to fire the code from another file:
quoteStatusHelper.GetQuoteStatus(QuoteID)
Then grab the result with
Dim returnedStatus = quoteStatusHelper.QuoteStatus
This seems really wrong, as the value seems to be held in the partial class after the first run. So if I have two users accessing the class the public shared dim is changed for both users! There must be a better way to do this. I have looked everywhere and I'm more confused now than when I started off...
How can I make QuoteStatus in the partial class unique to every user and access it from my code. I cant figure it out :( Please help
Many thanks in advance.
The problem is that your QuoteStatus variable is shared/static. You don't need to do that here. Declaring it as Public will make it visible to other classes. Remove Shared from the method and the QuoteStaus variable, and all should be well.
Once you remove Shared it will be an instance class, which means that you'll need to initialize it in your code:
Dim statusHelper As New quoteStatusHelper()
statusHelper.GetQuoteStatus("QuoteID")
EDIT
Taking a closer look at your code, it looks like you could make GetQuoteStatus a function that returns the QuoteStatus as a string, as #Claudio Redi suggested.
Public Function GetQuoteStatus(ByVal QuoteID As String) As String
Dim quoteStatus As String
Dim con As New SqlConnection
Dim cmd As New SqlCommand
Try
con.ConnectionString = ConfigurationManager.AppSettings("quotingSystemConnectionString")
con.Open()
cmd.Connection = con
cmd.CommandText = "SELECT Status FROM Quote WHERE QuoteID =" & QuoteID & ";"
Dim lrd As SqlDataReader = cmd.ExecuteReader()
While lrd.Read()
quoteStatus = lrd("Status")
End While
Catch ex As Exception
Finally
con.Close()
End Try
Return quoteStatus
End Function
By making GetQuoteStatus a function, you'll be able to get the value like this:
Dim statusHelper As New quoteStatusHelper()
Dim quoteStatus As String = statusHelper.GetQuoteStatus("QuoteID")
An option would be using a local variable on your method for quoteStatus and using it as return value of GetQuoteStatus. So you wouldn't use anymore the shared member QuoteStatus
EDIT
Added a function example. You should remove your shared member QuoteStatus from your class. I don't use VB on my day to day work so I hope I didn't make any stupid syntax mistake
Public Shared Function GetQuoteStatus(ByVal QuoteID As String) as String
Dim con As New SqlConnection
Dim cmd As New SqlCommand
Dim quoteStatus As String
Try
con.ConnectionString = ConfigurationManager.AppSettings("quotingSystemConnectionString")
con.Open()
cmd.Connection = con
cmd.CommandText = "SELECT Status FROM Quote WHERE QuoteID =" & QuoteID & ";"
Dim lrd As SqlDataReader = cmd.ExecuteReader()
While lrd.Read()
quoteStatus = lrd("Status")
End While
Catch ex As Exception
Finally
con.Close()
End Try
return quoteStatus
End Function
I made a basic program that connects and gets content from a table via SQL, it's working normally. What I want is; when connection losts via SQL Server or internet connection, it must continue to list items that it got before connection losts instead of giving "Connection Problem Error".
Code is like this:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim strSQL As String
Dim conn As New SqlConnection
conn.ConnectionString = baglan()
conn.Open()
strSQL = "SELECT * FROM Telefon_Otomasyon"
Dim da As New SqlDataAdapter(strSQL, conn)
Dim dset As New DataSet()
da.Fill(dset, "Telefon_Otomasyon")
Dim Hepsi As DataRow
For Each Hepsi In dset.Tables("Telefon_Otomasyon").Rows
Response.Write(Hepsi("Arayan") & "<br />")
Next
End Sub
Thanks!
What you can do is store your dataset in Session: (excuse my VB, i'm very rusty with it)
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim strSQL As String
Dim conn As New SqlConnection
conn.ConnectionString = baglan()
conn.Open()
strSQL = "SELECT * FROM Telefon_Otomasyon"
Dim da As New SqlDataAdapter(strSQL, conn)
Dim dset As New DataSet()
Try
da.Fill(dset, "Telefon_Otomasyon")
MyDataset = dset
Catch ex As SqlException
dset = MyDataset
End Try
Dim Hepsi As DataRow
For Each Hepsi In dset.Tables("Telefon_Otomasyon").Rows
Response.Write(Hepsi("Arayan") & "<br />")
Next
End Sub
Private Property MyDataset() As DataSet
Get
return Session("myDataset")
End Get
Set(ByVal value as DataSet)
Session("myDataset") = value
End Set
End Property
This is also a very basic example, it needs to be tidied up before you can use it in production code, i.e. you need to consider what to do if there is no dataset stored in Session (if it returns null). You may want to be a bit smarter than that and just store a specific table. Note that Session can expire though, so do some reading on it. This should be enough to steer you in the right direction.
Further note: if you want something a little less volatile than Session then you could try using the Cache instead.
I'm not sure I understand the problem here. While I'm not a VB-programmer it seems to me like once the page loads it will run the SQL query and then process that dataset.
If you reload the page and the SQL connection isn't working you will get an error that you'd need to handle somehow (not sure how VB exceptions work but I'm sure you can figure that out).
If you on the other hand mean that you want to get whatever data you can from a query that gets disconnected mid-query - I'd say that is pretty hard and only relevant for huge queries.