.net - Using SyncLock To Synchronize Access To List(of T)?
Nov 16, 2010
I have a class that contains a List(of T) used in a multithreaded application. I have three methods Get, Add and Remove where these access and modify the List(of T). I was using SyncLock to lock m_List any time I queried it for the desired object as well as when I added or removed objects. However I'm curious as to if there is a performance gain by simply locking m_List when I add an object or remove an object as opposed to when I'm searching for a desired object?
I have a List of objects shared by multiple threads, it sometimes generate IndexOutOfRangeException when trying to Clear. While searching for solution I found that I should use SyncLock while accessing the List. But my question if what is the importance of lockObject in SyncLock block E.g. while clearing myList
Can I use Synclock myList myList.Clear End SyncLock or lockObject should be different from myList?
What I think about sysnclock is "lock is obtained for object specified as lockObject". What if I specify list to be cleared as lockObject, shouldn't the compiler supposed to obtain the exclusive access to list before clearing it ?
I have a small application in ms access for student information. which is on my sever.now I have same application in .net and sql server which is online in my website, while access application is on my pc...Now I want that, If i make changes in my access application, the data must be copied to my online application automatically,Same thing i want vice versa,means if i make changes in my online application, the data must be copied to my desktop database.
I'm writing a desktop application that uses the main access database that will be hosted on a central server, but there will be a laptop with the app on that has an offline mode so records can be created offsite. When the laptop returns I want it needs to be synced back to the main database.
Has anybody got any pointers on a way to do this, I've briefly read about JRO but is there an alternative / better method?
Originally, I was just going to write some custom code to do this, but thought I'd check to make sure there wasn't something already out there.
I 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.
This is what I'm sure will be the first of many noob-ish questions from yours truly... I'm studying as a mature student for a Computing Degree (encompassing web design, hardware, programming and systems analysis). The programming seems to be my weak spot this year. I enjoyed C++ last year, doing basic console applications, but progamming visually with VB in Visual Studio 2008 I'm struggling!
I was just wondering if mixing SyncLock blocks and Monitor.Enter/Exit statements is dangerous. I know SyncLock uses Monitor and a Try block in the background, but are there any problems with using the two together for thread synchronization?
I am pretty new to multi-threading in general and I would like to know how can I lock a shared integer variable to not be accessed by other threads while it is read/updated by an other thread.When I try do do SyncLock myInteger, I get that error : Error 6 'SyncLock' operand cannot be of type 'Integer' because 'Integer' is not a reference type.
Here a simplified example of what I mean
Private Shared myInteger As Integer Private Sub MySub() SyncLock myInteger ' This does not work ' read/write a new value to myInteger End SyncLock End Sub
MySub is called by multiple instances of the class, and running in multiple threads?
Is there simple way to SyncLock an object that can be null? And before you ask for it, yes, I know that it isn't logical to perform a SyncLock on a null variable. However, that would simplify my code because right now, I have no choice but to perform a null check all over the place before calling a SyncLock.
I was wondering if this is known / expected behavior. By design?Is it documented somewhere?
My 'real' code does need something to keep one thread from accessing a listview while another is busy clearing and refreshing the Items collection, so it's not as easy as omitting the synclock section in the example below (The SyncLock in my case is on the ListView).
This code, which can be pasted over a new empty form's user code class, deadlocks during the Invoke call. It doesn't reach the entry point of SetText (setting a brakpoint there, the deadlock occurs before the breakpoint is hit).[cod]e...
I have an application that requires several threads, otherwise the main UI thread would end up frozen.i am after a little advice as i have not really don alot of threaded applications.
First Question;
I have a thread which handles data coming in from the serial port( this wil become much more complicated), is it safe to use a synclock on the serialport object : -
Suppose I have a byte array, Private Data as Byte(). This array is private within a class. The class provides public functions for reading and writing to Data. This class can be accessed by multiple threads, so I want to avoid a situation where reading from it and writing from it don't happen at the same time.
For now, I am using SyncLock to avoid issues. Can I put SyncLock Data in just the write functions, or does it need to be in the read functions? Or, both? I don't have a specific code example in mind. I am just curious if there is any benefit to locking for both read and write functions if the writing functions' SyncLock will make writing have exclusive access to it in the first place.
I'm trying to SyncLock my DataTable, to avoid problems with multithreading and stuff. But it doesn't seems to work. I'm trying to lock a DataTable wich is acceseed inside a nested for-loop:
vb.net SyncLock radiolopere For Each row As DataRowView In tableview
synchronizing a combobox with a textfield. I have a form with a textfield and a combobox. The combobox is populated with the department name from the database when the form loads. I would like the textbox to display the corresponding department number when the user selects a department name from the combobox. I have tried using the SelectedIndexChanged event of the combobox but I can't seem to code it to work. This is the code I'm trying to use but it is displaying "DEPARTMENT" in the textbox. Department Code is the primary key of the table.
strSQL = "SELECT * FROM DEPARTMENT" Dim da = New OracleDataAdapter(strSQL, cn) da.Fill(dSet, "DEPARTMENT" )
I'm trying to get my application to restore the default values of my application settings but every time I click the Synchronize button it says: No user.config files were found in any of the following locations. I have never before tried to synchronize this application and am working with Visual Studio 2010. [URL].
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged If ListBox1.Text = "kg" And ListBox2.Text = "lbs" Then
I have my client app installed in many computers, each computer is connected via LAN. Each Client app uses its own SQL database. I need to synchronize the databases in each computer so that every client app has the same data. How can I achieve this using VB.net (VS 2010 , Winforms)
I have two datagridview with same columns. When user resize the column of one of the datagridview during run time, then another datagridview column will synchronize to resize as well..
With my program I wanted to change the fixed connection string to a User entered one. So in the application settings I added DBConnectionString as a user define String. If the string if empty, it shows the window where one can add the server, database and user name / password. If you press the OK button, it saves the settings:
Private Sub LDBOKBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LDBOKBtn.Click ' ----- Server name is required. If (Trim(LDBServer.Text) = "") Then MsgBox("The Server or Host name is required.", _
[code]....
The problem is that when you press the same button to show the System Settings again, the ConnectionString is empty again. So nothing was saved.
I have written a stupid backup utility that copies new or modified files. That's fantastic until I come across files that are 11 GB in size that have been modified. I have a feeling I can compare the file to be backed up and the file that will be over-written (old version of file) and "synchronize" the file instead of copying the entire 11 GB.
How can i synchronize dragged controls (in my application), so they maintain their relative position to each other? is there some API function or .net method that can do this?
Once again Invoke has come back to haunt me! I have an application that has some background threads, serial communications and obviously a GUI. Now, the serial ports received incoming messages as events and these get processed and incoming data is logged both to a file and also appended to a RTB in the GUI (done using Invoke if InvokeRequired is true).Now, under normal circumstances everything is super happy and runs quite nicely but when stressed I reach some sort of deadlock.
What happens is I have two methods AddOutput and RemoveOutput. These both sync over an object SyncOutput As Object. When messages are received on the serial port they are processed and depending on whether or not a response is required AddOutput is called. This adds out going messages to a dictionary which is then accessed by a thread and the messages are sent out. If an acknowledgement message is received then the corresponding message in the dictionary is removed.
If completedOrders.Count <> 0 Then For i = 0 To completedOrders.Count - 1 SyncLock completedOrders 'Do some work, for example this: Dim text As String = completedOrders(0).getCN & " " & completedOrders(0).getDeviceName & " " End SyncLock Next End If Is a synclock needed before the if statement or for loop? In other words. When you call methods like .length or .count is it necessary to synclock them or can another thread be writing to it at the same time. CompletedOrders is a generic list of a class.
Ok so I coded this app that generates a number/word and it will upload to my database. Speed wasn't the issue when my db was under 1million entry. Now that I got about 100million entry it takes a few mins to upload.I worked with threading before but now I want all my threads to access this function that will give them a string. Now here is the problem, if 2 or more thread access the function at the same time, it will crash.How can I by pass that?I read about SyncLock. Can I use SyncLock on my function on each thread?
I've got an XML file which is a pain to manually update. So I was thinking of creating a small app which synchronizes this data for me based on data from an Excel Sheet or something.
I sometimes come across patterns or common practices that I do not agree with. I have a clear opinon of what is considered "good design", which is mainly based on my understanding of abstraction and creating layers.IMO, the core of an application is it's object model. It's a hierarchic model where one object references other objects or lists of them. That's a memory-internal model. For example, a house object references a list of rooms referencing lists of furniture.An object is identified by it's reference. There are no IDs or PKs in that layer.Saving/Loading data is an additional feature. Sure, no application will do without, but it's based on top of the core of the application. I could write an application that works very well without loading/saving, and for version 2 I will think about whether to save data to a database or an XML file. Merely this fact proves that a database layer is not the lowest. I've never agreed with that three-tier model - even if you call me unteachable.
In addition to all application objects, there are Datasets - and that's my problem now. They can be considered as a copy of what is already present in the application's object model. Its from a different, table-oriented view. As both structures exist in parallel, there's the need to synchronize the DataSet with the (rest of the) application's objects.That's the task that I am always struggling with, and I ask how you handle it. I know this is a major design question but, fortunatelly, I could quite get around this problem so far.The only solution I can imagine is maintaining additional relation lists. For example, whenever the property of a room object changes, that change must be reflected in the associated DataRow in the DataSet. For this purpose, I need a look-up table that tells me the PK of the given room in the database. It requires a lot of additional efforst to do all the synchronization.Again, the house or room object itself does not have a PK and it won't get one because on that layer, it doesn't even know that a database exists.
I am using Mail.dll Commercial component. I can read the unseen or unread messages in my windows application. IF i open the mail using the [URL] then I cannot get the mail in windows application. Is there any way to synchronize the gmail mails
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?
