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Hi guys,
I am not sure if this should be VB specific or more design but i'm a bit stuck with a dll i try to write. This dll should take care of communication with our server (tcp) and download files. Then this dll can be used by various host applications that need connection with our infrastructure. Now i want to build a download queue which in the back is downloaded ( backgroundworker ) and where i can add downloads selected by the app (it's about music and video files). This "queue" needs to be exposed to the host application so they can see the queue and what is happening..
However.. first i thought of doing this using our database ( we use sqlite for the communications DLL).. however.. sqlite and multithreading don't get along AT ALL.. so this locked the database giving all sorts of evil errors (and worse.. sometimes blocked the TCP Socket from writing data into the local database which takes priority over the downloads
Then i wanted to do this using a datatable but this too gives all sort of strange issues which just seem to send me in a loop (exposing the queue using a dataview.. the connected datagridview doesn't refresh as it should, when row is selected that is downloaded and then gets removed from the view we get "isnull" errors etc, etc, etc)
Now my ideas are out and i turn here:
What is the best way to build a download queue which:
Needs to be able to prioritized
needs to be visualised like our background thread is using it (so with the priority in place)
Where multiple threads can add / remove downloads from it..
Can anyone point me in a right direction ?
Many thanks !
Do Or Don't, there is no "try catch ex as exception end try"
modified on Sunday, December 28, 2008 9:42 AM
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It sounds like you need a priority queue and a way to retrieve some status information from it. It also sounds like you have the priority queue in place. Use locking for queue access and modification. I'm a C# developer and don't know the VB.NET syntax, but in C# there's the lock keyword that can be used to lock a section of code for execution by a single thread. It's pretty simple and the most common technique is to create a locker object that is locked in every place the queue will be touched. Depending on your needs you may want to go with a subscriber model to provide information to other applications. With it you would have queue modification events that other applications 'subscribe' to and they would implement an event handler that will give them an EventArgs object with information about the event (ItemAdded, ItemRemoved, ItemUpdated, ItemProcessed, etc.). Or, perhaps you want to go with a by-request model in which you have methods that return a status object only when invoked. Using .NET Remoting may be useful if it is a Client-Server architecture as the TCP/IP communication is already handled for you and it defaults to using a Singleton, where one instance of the priority queue will exist on the server and clients can interact with that instance remotely.
Keep It Simple Stupid! (KISS)
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Hi,
I am trying to create a VB.NET application which can open a browser and login using a username and password from the application. And then after login use it to search for values passed by the application.
Can this be done??If yes how can yo just give me the code to open browser and pass values.
thanks for your help.
Shrey
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I won't give you any code, but you could take a look at the WebRequest, WebClient and other related classes in the System.Net namespace. I think these will do what you want without having to open up a browser window.
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I beleive there may be an article here for scraping web sites, that should get you started.
Never underestimate the power of human stupidity
RAH
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Dose anyone have any code that will allow me to change the backgound color of a Windows Mobile Toolbar in VB.
Thanks in advance as I know this code can only be wrote by the pro's.
Mark
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Hi!
I'm trying to run a process that updates a zip/tax rate table.
The new tax rates are in a flat file. the table I need to update is a FoxPro free table indexed in country and zipcode fields.
Everything is working, but I have 45K+ records to update and after about 15% into the flat file the process it gets slooooow and gets slower and slower.
If I comment out the code that does search and just leave the code that goes through the flat file it takes about 30 seconds with the looks up and update it takes 30+ minutes and I can see the progress bar miving for first 15% and than it dies.... I think I am missing something here...
Here is what the code looks like:
m_conn = New OleDbConnection
m_conn.ConnectionString = "Provider=VFPOLEDB.1;" & _
"Data Source=" & g_app_options.processing_folder_path & "output\tax import;" & _
"Mode=ReadWrite|Share Deny None;" & _
"Collating Sequence=MACHINE;"
m_conn.Open()
Do While srTaxFile.EndOfStream = False
ado_command = New OleDb.OleDbCommand("SELECT ZIPCODE FROM zip WHERE country='001' AND ZIPCODE='" & taxRecord.field(cTaxRecord.RecordFieldIDs.ZipCode).Trim & "'", m_conn)
Dim sZipCode As String = ado_command.ExecuteScalar()
ado_command = New OleDb.OleDbCommand("UPDATE zip SET itaxr = " & taxRecord.field(cTaxRecord.RecordFieldIDs.SalesTaxRate).Trim & " WHERE zipcode='" & taxRecord.field(cTaxRecord.RecordFieldIDs.ZipCode).Trim & "'", m_conn)
ado_command.ExecuteNonQuery()
set_progress(srTaxFile.BaseStream.Length, srTaxFile.BaseStream.Position)
Loop
Its pretty simple, and I don't understand why it takes that long. This is running on a local drive.
If you can help or know what I'm missing, I would greatly appreciate it!
Thank you
ipokrov
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Sorry but are you trying to update a table based on values from a flat file? Also, why are you selecting first if you know what you want to update?
You should also look at Transaction--this might make the process faster but I am sure there are better ways to do what you need to do. Can you please explain what you want to do, in plain English, without any code?
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Hi,
Sorry I was not clear on what I'm trying to do.
In plain English, I have a comma delimited file with 45k+ records that contains zipcode and taxrate. I have a foxpro table that contains countrycode, zipcode and taxrate fields. Now I need to update each taxrate field in the table with value of taxrate field from the flat file. If the zipcode in taxrate table is not found I need to insert a new record. (that is why I have to lookup the zipcode first, I commented that code out and did not include it with my example.)
Thank you
ipokrov
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FoxPro has indexing on it's tables using either IDX or CDX files, they'll have the same name as the .DBF file, but with a different extension; that is if there are any indexes on the table. Hopefully, there is an index on the zipcode field that can be used to speed up the look up queries. From my experience with OLEDB, it's generally faster to send as few commands as possible, so build a single query like:
select zipcode from zipcodes where zipcode in (... comma-separated list of zip codes ...)
This query of course will perform much better if there is an index on the zipcode field. It will give you the list of zipcodes that exist and need to be UPDATEd and ones that aren't in the result set will be INSERTs.
Keep It Simple Stupid! (KISS)
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Hi All...
I am trying to load xml file with code mentioned below.
Dim XMLDc as XML.XMLDocument
XMLDc.Load(file.Path)
The problem in above is some file is getting uploaded where as xml file is not. It gives error 'Check the path' where all file is in same folder.
Say the path is "D:\Project" there is 3 files 1.xml, 2.xml, 3.xml
1.xml & 3.xml is getting uploaded and 2.xml is not. Generate Error 'Check the path and file should exist'
Please explain me the error and how to solve it...
Thanx in advance...
Shazz here to help you...
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There is nothing that would cause that error for only one of the files that you described.
Shazz Rock wrote: Say the path is "D:\Project" there is 3 files 1.xml, 2.xml, 3.xml
Say what the real file names are instead. Also, where do you get the value for file.Path?
Despite everything, the person most likely to be fooling you next is yourself.
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I have a treeview in my form and when I inclrese the font of tree node it trims the text and do not increase the width of node. can anybody help me to sort this problem?. thanks in advance
Jagsir Singh (Sanam)
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Increase the width of the TreeView control??
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Hi, Everyone
I have me own web company called HoskWare i am looking for people to work with in building web browsers,
There are many great web browsers these days such as (Internet Explorer 8) - (Mozilla Firefox) - (Opera) and others
How ever i am trying to gather some people so we could make a web browser better that is better than them all put together.
If anyone is interested please contact me at:
MSN - ash-hosk@hotmail.co.uk
Thanks,
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There is a jobs board on this site. Perhaps you could look for employees that way?
And if you do, you might also want to check your grammar. I don't like seeing simple gramatical errors on CVs I'm reviewing and it doesn't make such a good impression the other way around either.
113st4life wrote: I have me own web company
me --> my
113st4life wrote: i am looking
i --> I
113st4life wrote: web browsers,
Sentences end with a full stop, not a comma.
113st4life wrote: such as (Internet Explorer 8) - (Mozilla Firefox) - (Opera) and others
List items in prose a typically demarked by commas. Why are your list items in brackets? Finally, you've not put any puncuation at all to indicate the end of this sentence.
113st4life wrote: How ever
However is all one word.
113st4life wrote: i am
Again, the first person pronoun should be an upper case "I".
113st4life wrote: Thanks,
Your final sign off ends in a comma rather than a full stop.
I would have serious doubts about working for someone that cannot master the basics of communication.
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Colin, you must have terrible trouble dealing with the Yank bastardisation of the language.
I was enlightened by your exception article, thanks.
Never underestimate the power of human stupidity
RAH
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I was looking for people to work with me not for a lesson!
I wasn't bothered about all that stuff you said its just a simple message!!
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After long time I opened the Crystal Report
I got the following error message on the line that declared a ReportDocument. In addition, when I tried to open any Crystal Reports that I created in Visual Studio 2005, I got "Crystal Reports ActiveX Designer: Failed to open document." and "Microsoft Visual Studio: Failed to create the Crystal Query Engine." error message.
But before it working properly.
Plzzz Help me. Thanking you
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Hello sir,
I want similar coding for treeview, where for linklabel is as follows.
[CODE]
Private Sub LinkLabel8_LinkClicked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.LinkLabelLinkClickedEventArgs) Handles LinkLabel8.LinkClicked
WebBrowser1.Navigate(Application.StartupPath & "\source\test.html\")
End Sub
[/CODE]
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I solved this, use file name in the tag with this extension and use the below coding
WebBrowser1.Navigate(Application.StartupPath & "\Source\" & e.Node.Tag)
IT Professional.
Work till you get it!
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i need how to use crystal report with vb.i install crystal report 10.
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Given that VB6 was a dead language when CR 10 was written, I doubt this is possible. either way, VB6 was rubbish even when it was supported, why are you using it ?
Christian Graus
Driven to the arms of OSX by Vista.
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i need the code.how i use crystal report with visual basic 6.i need this code.
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