I have a small code that can start multiple threads in numerous numbers and these threads will perform some calculations and file operations (read and/or write) that are private to themselves (each of the calculations and file operations are independent).But I can not figure out how to make the connection for threads to file operations.
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I want to make a simultaneous connection to multiple servers with threads, only to create a single connection.
Imports System.IO
Imports System.Net.Sockets
Imports System.Text
[Code].....
I have an application in which I am running a separate thread.
Dim thread As New System.Threading.Thread(AddressOf Main)
thread.Start()
However, the thread makes reference to an textbox named Output, and it generates this error upon execution:
System.InvalidOperationException was unhandled
Message="Cross-thread operation not valid: Control 'Output' accessed from a thread other than the thread it was created on."
Source="System.Windows.Forms"
(message shortened for space)
How can I make the operations run on another thread, but still use the Output object? I cannot call a subroutine to do that for me, as it generates the exact same error.
The method called is AppendText, by the way.
I am trying to make a calculator that accepts multiple operations, similar to the calculator found on Windows.
View 6 RepliesI want to perform two hashing operations concurrently on a single file, without reading the file twice. Is there some way to share the FileStream between two synchronized hashing threads? For example:
Dim Stream As New IO.FileStream("...", IO.FileMode.Open)
Dim HashA, HashB As Byte()
Dim A = New System.Threading.Thread(Sub()
[code]....
Maybe some way of caching a stream? Trouble is, I don't want the entire file in memory at once (it could be many gigabytes in size) and I don't want the file read more than once, due to speed issues. I want the file cached only sufficiently to ensure that both threads can work.For example, suppose at some point in time, thread A had read 100k of the file, but thread B had only read 20k of the file. The portion of the file between 20k and 100k should be cached; but then progressively forgotten as thread B catches up. Then again, if thread B is too slow, we might still end up with hundreds of megabytes being cached.Maybe thread A should be made to wait while thread B catches up. Maybe the ReadByte() function of the stream should block for a while if one of the threads is too far behind?
how i can make 2 threads in server ? "in server 2 threads . the first for + opration and seconed for x opration" client send to server 2 number and opration "+ or x"
[Code]...
The file operation calls are returning before they are actually complete, or the disk is being cached somehow. What is happening here is that a zipped file containing a number of files to be updated on the users machine has been unzipped and the filenames are returned in an array called 'newfiles'. Each actual file unzipped is temporarily preceded by a '~' character. We rename each existing file to <filename>.old, then delete all the old files. However, sometimes when the code runs, the old files are not deleted. The only explanation for this I can think of is that the second 'Fileexists' is not seeing the files because the filesystem has not caught up at that point. I've never seen this behaviour documented anywhere, though. It works fine when single-stepped.
For Each fn As String In newfiles
If .FileExists(fn) Then
'rename existing file to .old
delpath = Path.ChangeExtension(fn, "old")
.RenameFile(fn, delpath)
End If
'rename the new file to correct name i.e. remove "~"
[Code] .....
Say I have some code that does this:
Public Function AppendToLogFile(ByVal s As String) As Boolean
Dim success As Boolean = True
Dim fs As IO.FileStream = Nothing
[Code].....
First of all: is it a problem that I have that Try/Catch/Finally block inside of a SyncLock?
Second of all: suppose this code runs, on an event, potentially many times within a small timeframe--say, ten times in one second. Is it OK to have it SyncLock like this, or would it make more sense to have it add a line to a Queue, and then write all the lines from the Queue to the file on a timer that goes off, say, every second?
I am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for ths text file opearations. s
View 1 RepliesI would like to know if there is any opportunity in VB.Net to use atomic operations. Or Maybe there is an opportunity to check if a file is allready in use or opened.The reason why I ask is because I got a little application that I would like to log its actions. As the applications uses threads the method for writing the log file sometimes is trying to open the log-file more than once which leads to an exception.
View 3 RepliesI am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for this text file operations.
View 2 RepliesI am trying to stop the following piece of code from taking up too much processing power of the PC by using threads. But I keep getting errors when I use threads:
[Code]...
I'm using 2 System.Timers, which spawns a worker process during its elapsed event. If 1 of the events is busy doing something, the other thread elapsed event doesnt fire until the 1st thread has completed.Is there any way I can make both threads continuously fire its elapsed event??
View 3 RepliesI just had a new, last-minute idea on to take on a task, so I am running to StackExchange for quick help.
What I want to do is execute a series of methods right in a row, each in their own threads. I want the application to wait until all of these threads are completed, after which the program will resume. It also has to use managed threading (thread pool).
What quick examples could you provide to help me along the way? If it's too complex, what things should I know about so that I can Google it on my own?
I have a main thread which is designed to be a batch processor - it spawns a series of 'child' threads from a loop (which can vary in terms of the no of items) - see below
[Code]...
However, each of the 'child' threads could take anywhere from milliseconds to about a minute to process - depending on the complexity of each calculation. There may also be a large number of child threads - e.g 100s. Creating large numbers of child threads is not efficient. I therefore want some way to effectively queue each child thread (and cancel if the process is taking too long to complete). Autoevents seems like one way of doing this, but the only examples I can find seem to assume there are two different processes on seperate threads, not one process being repeated.
I'm trying to figure out some Excel automation. I have a form set up so the user can click on a label to open an Excel file (as a background process I guess) so the file isn't actually visible. Once they click on the "Convert to Count" button it will multiply all the values in Column B by 1,250 and put the output in Column C. Once it has finished this action, it makes the file visible so the user can choose to save it or not. Also, some users have Excel 2003 and some have 2007. Would it be possible to be able to load both xls and xlsx?[URL]..I must say I am very new with .NET and have a little bit of knowledge with VB6. I'm not sure where to even begin. I've looked up some ways to load an excel file but couldn't get it to work the way I need it to. Most of the ways I found were loading the file into a DataGridView. I don't want to use a DataGridView if I don't have to. Some of the files the users might be loading could have 10,000+ rows and that would take too long I think.
View 3 RepliesI'm trying to make a multi-threading app which extracts the names from my site. I have 1000 pages celebrity related. The urls are on a listbox List1 and the number of threads are specified in TextBoxThreads I would like each thread take care of a coresponding url on list, when they finish go to the next one and so on (for each thread a url)
[Code]....
I'm facing a problem after installation any software setup that has a database in access(mdb file) How to I transfer file path in our connection string.
View 3 RepliesMy scenario is that I have a Windows service running as SYSTEM. That means no network rights by default. I want to copy a file from server A and server B. Both require different Credentials.Normally, I use Impersonation on one thread to access another server [URL]. The problem is that one thread can only impersonate as one user. And I need to access server B as well.So, I wonder about the best way to copy between two threads. I am interested in doing this in memory, for speed and I do not want to save a file locally on disk in between.
View 3 RepliesI just made a rapid file transfer form for my photos.In which I drag photos into a listview with my destination folder set.I assign each individual file transfer to a new thread. This works very fast as compared to the standard drag n' drop.
View 2 RepliesI am using Synclock to prevent multiple threads from logging text messages to the same file at the same time, but this doesn't seem to work:I get frequent sharing errors on the logfile, within the synclock block.The Synclock is using the variable holding the filename, because it exists all the time and because it is always the same object, whatever class instance or thread I'm in.[code]Despite using Synclock and a Using block around the code, I keep getting this error in the sw.WriteLine(Msg) line:System.IO.IOException: The process cannot access the file '(filename)' because it is being used by another process.Should I use some other type of object than a string to synchronize on?I cannot use a user interface object (button or so) because it is a windows service project.It was written and compiled in Visual Studio 2008, but targeting the 2.0 framework because it has to be able to run on some old Win2000 machines.
View 12 Repliesi know how to make a tcp ip connection using tcpclient and so on. But what i want to know, how to transfer file in a specific computer?
View 2 Repliesam using vb 2005 with an access database 2003 vb.net website (aspx page) i am try to put contact details in to the database with six text boves and one button (Button1) to submit the informaton in run time (aspx page) when i run the page no problems then i click submit no error but it does not send the information to the dadtbase.i put the code when i double click on the button here is my code could you plz tell what i am doin.
HTML
Imports System.Data
Partial Class accessall_NewCustomer
[code]...
I am using the following connection string to connect to a sql server on my network but having all kind of problemhere is the connection stringosqlconn.connectionstring="server=xxx.xxx.xxx.xxx,1433;" &"Database=LOS;" & "Integrated security=SSPI"I dont know if the problem is that there is no ";" at the last parameter like the others but I get the following error that shows in the file
View 24 RepliesHow do I make the connection to a SQL database (one to many), with VB.NET?
View 1 Replieshow to make connection with my database access with visual basic 2008.
View 2 RepliesI can't find the vb.net code to make PHP connection while read the script before it would redirect to mysql database. As I have store the local host in the php script with the username and password, so I would not need the code for mysql at this present moment.
View 5 RepliesI need to make a connection with an access 2007 database in VB 2005.[code]....
View 15 Repliesregarding vb 2008 as below 1.how to make connection between mysql and visual basic 2008. 2.how to write insert the query.
View 2 RepliesI tried to make my ODBC Connection within the class. here's my class code
Public Class Library
Public Function Seek(ByVal Connection As Odbc.OdbcConnection, ByVal TableName As String, ByVal Field As String, ByVal Index As Long)
[Code]....
Here's my error: Unable to cast object of type 'System.Int32' to type 'System.Data.DataSet'. I am using VBdotNet2005
