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Hello all!
DataSet object is never disposed! I derived my own class from DatSet, added destructors to it then, and the problem is I NEVER get destructor called!
Is it right? I never get any of created objects of that class to be collected by GC.
Is it right? Or I miss something?
Thanks in advance.
Regards,
alexx.
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Has anyone ever had luck type-casting them from standard classes before? ie. a "UserDataTable" from DataTable?
Even with matching constraints I get errors. Shouldn't it be possible?
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If you've got a DataTable that's been returned from some general procedure which doesn't know about your derived classes, you can't cast it to a derived class - because it isn't one. The object's actual type is carried with it.
You should be able to write the data to an XML format using DataSet.WriteXml and read it back using a typed dataset's ReadXml method.
Stability. What an interesting concept. -- Chris Maunder
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I am programming a program to use modem dialup to retrieve data from SQL 2000 Server...
What would be a good solution for the connection betweeb a client PC and the server running SQL Server 2000?
JW
DJ
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I have an SQL Server 2k (personal edition) running on Windows 2000 Pro for testing.
I tried to connect from other PC running SQL server to this databse. However,
from SQL Query Analyzer on the local PC, I could not find the database once I clicked on the ... which is right to the SQL Sever: text box.
The connection between the PC and the Database machine is modem dialup. From either side, I can ping to each other without any problem.
Moreover, once I connected my PC to the intranet, I can access/login to any SQl server database which is within the intranet environment.
ANy help are greatly appreciated.
JW
DJ
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The box that appears when you click the '...' button is filled using broadcasts to the local subnet, on UDP port 1434, or by using NetBIOS broadcasts. It's unlikely that this will work over a dial-up connection, because routers do not forward broadcast messages.
You'll need to specify the server explicitly. This may not work using names for the same reason as above, so you may need to use an IP address.
Stability. What an interesting concept. -- Chris Maunder
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Hi all,
I'm encrypting some private information into a SQL but now I got
an issue where my users want to be able to perform searches on
these encrypted columns. I could limite them to exact searches but
for sure they will complain about that so I will have to provide
search where I can use the LIKE operator.
The encryption happens before I store the data into the database.
Any ideas?
Thanks in advance.
Alberto
OHSAH
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Hello all,
I am developing an ASP application using SQL Server as my RDBMS. I need to create a new ulogin and user and assign the user to a specific database. I have done that and works ok. Now I need to create a few tables and views that only the new user can access and I go:
<br />
CREATE TABLE @myNewUser.[MY_TABLE_NAME] (...etc...etc...)<br />
Obviously this doesnt work. Can anyone tell me how to do this?
Thank you
theJazzyBrain
Excelence is not an act, but a habbit Aristotle
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In a stored procedure where you pass in @newUserName and @tableName to the procedure:
<code>declare @stmt varchar(1024)
set @stmt = 'CREATE TABLE [' + @newUserName + '].[' + @tableName + '] ...'
exec @stmt
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thanx...
theJazzyBrain
Excelence is not an act, but a habbit Aristotle
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I'm developing a shopping cart using vb6. (ActiveX dll)
For db connectivity I'm using ADO 2.7
The database (free tables) in use for now will be FOXPRO (I know not the best choice)
At some point the databases will be converted to MSSQL.
My question is:
When the cCustomer class is created, can I open the connection to the database and closed it when class is destroyed (on session end)?
Or
Should I open and close connection as needed?
It just seem better to just do it ones, but I'm not sure on how much extra load it will be on the server.
There might be up to 500 people on the server at any given time...
Please let me know what you think
Thank you
Iluha
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To do this project personally.
I would use a MS access DB (crap but suited)
Create your pages and then store the products buy within an Array which begins size one and then dynamically grows as you insert more items to the basket.
To dynamically increase the size of the array while maintaing the content of the array use "Redim"
Also when the person moves page to page store the array within a session
Atul
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Holding a connection open to a database as you're thinking doesn't scale well.
Use a combination of "just in time" connections, caching (ASP.NET caching is pretty nifty,) and a session shopping cart using an ArrayList of order items should do the trick.
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I had a DBA once who stored the UserId created by MSSQL in a table. After a while, usually after lunch, strange effects occured. People started to see other peoples data. After a while we figured out that when the connection is dormant for a while the connection drops and a new one is created when needed. MSSQL does this all by itself.
So i dont think you can get a connection all to yourself, you share it with others. Perhaps there is a way to keep the connection alive but why would you want this.
HTH, Grtz,
Guus
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hi,
i am using ms access.
how can i select only 2nd record in the records returned?
"select top 2 .... " can only get 1st, 2nd record
"select * limit 2,3" can only use in mysql.
any method to get the 2nd record in the records returned?
pls help!
thanks,
jim
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If you use an ORDER BY in your query, you could turn your original query with the TOP 2 into a subquery and select it again but reversing the direction of the ORRDER BY and setting TOP 1 on the outer query.
EuroCPian Spring 2004 Get Together[^]
"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar
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I populate my object with data from the database into arraylist. Later I perform add data using the ilist components to the object. The problem now is how the changes in the object will take effect on the database? Do I need to perform insert command to database and add into object at the same time.Please HELP!!!!
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What language are you using? IF you using .NET platform why don't you use DataSet instead?
Mazy
"A bank is a place that will lend you money if you can prove that you don't need it." - Bob Hope
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How do I get minor errors in OLE DB Provider. Like if I get E_FAIL, how wd I get the minor error associated with it?
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you have everything in HRESULT i dont thing there is anything related to minor code.
you have the following things.
HRESULT_CODE
HRESULT_FACILITY
HRESULT_FROM_NT
HRESULT_FROM_WIN32
HRESULT_SEVERITY
pick your choice now.
P.R.A.K.A.S.H
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No, you have a result in HRESULT; generally this is E_FAIL. However, mostly, you can then use IErrorInfo with the i/f that failed to get more useful information. I'm fairly sure, for instance, that in the ATLDBCLI.H shipped with VC6.0 there's a function that you can call to rip the info out and dump it to a trace window (OutputDebugString or ATLTRACE). You could check that function and see how to do it yourself.
Steve S
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Hi,
I am developing a Windows.Forms app. I am using a multi tier architecture with databinded strongly typed datasets . I am using a data access component called Facade where I have a method:
public Sub LoadCompany(ByVal companyID as Integer, ByRef ds as CompaniesDataSet)
ds.Clear()
...code to set the parameter in the select command
DACompanies.Fill(ds)
End Sub
It seems that ds.Clear() takes more and more time to complete , from a few miliseconds at start to 4-5 seconds after 100 method invokes.
Anyone has an answer to this?
Thank you,
Dan Bunea
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It would be helpful if you could post approximate sizes: how many tables are in your DataSet? How many rows in the DataTables? How big is a row?
I suspect you're suffering from a mid-life crisis[^]: the garbage collector is having to collect a lot of medium-aged objects. Instead of passing in a reference to a DataSet, you should probably just create a new one within LoadCompany and return it. Turn LoadCompany into a function:
Public Function LoadCompany(ByVal companyID As Integer) As DataSet
Dim ds As New DataSet
' ...
DACompanies.Fill(ds) Keeping the dataset around typically does you no favours, it just wastes memory. A DataSet object is not terribly expensive to create.
Earlier today I was looking at System.Data.dll using Lutz Roeder's Reflector[^], which seems to indicate that Clear doesn't delete any tables already contained in the dataset. It empties them, yes, but doesn't delete them. The DataTable keeps its DataRows in an array, whose size doesn't change when Clear is called (although the rows are freed). You might find that memory is being wasted if a large number of rows have been used in the past.
If you do decide to keep the DataSet around, Reset will clear any contained tables.
Don't fight the garbage collector.
On a final note, there's no need to pass a reference type by reference, unless you want to make the original reference (in the calling function) point to a different object. It's important to understand the difference between a value and reference type. I simply think of a reference type as being the same as a C++ pointer.
Stability. What an interesting concept. -- Chris Maunder
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Hi,
Thank you for your answer.
The DataSet is bound to very many controls (about 50) so reinitializing it is not a solution, because I lose my bindings (of course during load they are suspended, throught their binding context).
I have posted a more detailed explanation about this (with screenshots and code) at:
http://www.geocities.com/danbunea/posts/DataSetClear.htm
Could you tell me more about using Reset() because MSDN documentation doesn't seem to offer too much info.
About ByRef you are right, I could have used ByVal.
Thank you very much for your answer.
Dan
Dan
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I see you're using a typed dataset generated by Visual Studio from an .xsd file. Using Reset on a typed data-set doesn't help, it just breaks the association between the typed DataTable-derived classes and the DataSet's Tables property. It therefore clears the data the first time, but subsequent calls to Reset do nothing. My bad.
I wonder whether retaining the complete set of data (i.e. for all companies) and using a CurrencyManager object to manage the currently displayed company would work better than clearing the dataset when fetching the next company's data?
Looking at your code again, I note that you're passing the dataset to Fill, not the dataset's typed data tables (objects derived from DataTable). If you don't have a DataTableMapping assigned to the DataAdapter, I believe the new data will be added to the DataSet as 'Table' (if you have multiple result sets returned from the query, the second result set will be returned as Table1, the third as Table2, etc). I don't know if this is happening, but it may be better to bind directly to the tables.
Me.DACompanyContacts.Fill(ds.CompanyContacts)
Me.DAGrades.Fill(ds.Grades)
Me.DAQuestionsLookup.Fill(ds.QuestionsLookup)
Me.DAEmployees.Fill(ds.Employees)
Me.DAInvoices.Fill(ds.Invoices)
Me.DATrainingCourses.Fill(ds.TrainingCourses)
Me.DATrainingNeeds.Fill(ds.TrainingNeeds)
Me.DATrainingPlans.Fill(ds.TrainingPlans)
Me.DACompany.Fill(ds.Company) This may be worthwhile anyway because the work to go through the schema mappings is quite extensive. If it is happening, you may have a lot of stray DataTable objects hanging around.
I can't see any other problems with this code, so I'm assuming that it's a memory problem. You may want to try the CLR Profiler[^] to study the memory behaviour of your program.
Stability. What an interesting concept. -- Chris Maunder
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