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.NET Column: Safe Thread Synchronization

Posted By:      Posted Date: August 21, 2010    Points: 0   Category :ASP.Net

By far, the most common use of thread synchronization is to ensure mutually exclusive access to a shared resource by multiple threads. In the Win32® API, the CRITICAL_SECTION structure and associated functions offers the fastest and most efficient way to synchronize threads for mutually exclusive access when the threads are all running in a single process.

Jeffrey Richter

MSDN Magazine January 2003

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Concurrent Affairs: Build a Richer Thread Synchronization Lock


In my last column, I showed the various thread synchronization mechanisms employed by the Microsoft® . NET Framework (see Concurrent Affairs: Performance-Conscious Thread Synchronization). I then examined the performance characteristics of all these mechanisms and determined that the Interlocked methods performed the best because the calling thread never has to transition to kernel mode.

Jeffrey Richter

MSDN Magazine March 2006

Concurrent Affairs: Performance-Conscious Thread Synchronization


In my career, I have architected and implemented many thread synchronization techniques. This has provided me with a lot of experience that has shaped the way I now think about thread synchronization problems.

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MSDN Magazine October 2005

Basic Instincts: Thread Synchronization


My last three Basic Instincts columns have examined techniques for using asynchronous delegates and creating secondary threads. Those columns demonstrated how to introduce multithreaded behavior into your applications.

Ted Pattison

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.NET Column: The CLR's Thread Pool


How does the thread pool work in the CLR?

Jeffrey Richter

MSDN Magazine June 2003

ThreadPool with lock isn't thread safe

Hello, I'm having some problems with my code which apparently isn't thread safe at all. The problem is that it doesn't crash often, but of course it does when in production! I have twisted my mind around the problem for a month or so now, and I need some help in sorting out the problem. Well, the problem is that it isn't thread safe, and the collection (_subscribers) is modified while looping. The error says that it crashes in the method: SendRoundSettings. Here's part of the code (which I guess contains the error, as the other methods are pretty much identical): [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple)] public class DuplexService : IDuplexService { private readonly object _syncRoot = new object(); private static Subscribers _subscribers = new Subscribers(); private static RoundSettings _currentRoundSettings = new RoundSettings() {CompetitionId = 1, NumberOfAthletesInRound = 0, Round = 0, SortDirection = SortDirection.ByStartNumber}; public void SendJudgeScore(CompetitionJudgeAthleteJump judgeScore) { ThreadPool.QueueUserWorkItem(state => { Subscribers clonedSubscribers = CloneSubscribers(); Console.WriteLine("Sending judgeScore to {0} client(s)", clonedSubscribers.Count(x => x.CompetitionId == judgeScore.CompetitionId));

C# Thread Safe Class events

Right now I have created a custom base class that has numerous events.  These events have non-standard signatures and are fired from a thread I have that is basically just a while loop checking variables against older ones for telling when something has changed. As far as I know this is the best way to go about doing this is to just make a void on another thread in a while (true) loop, in the loop just doing ifs... than doing a thread sleep.  I make sure the thread is a background thread that way it'll exit propertly when the consumer exits.  If anyone knows a beter way of going about this than stop reading here. :) If not that onto my real question... I have events that are fired from this loop on the thread I created, now they're attatched on the consumer app and no matter what I do I can't seem to get these events to be thread-safe so that I don't have to use the Control.Invoke method for each event. If anyone knows anything that'll help me out it'll be much appreciated. Thanks,Chad

Are non-static objects thread-safe in a static-method?


I am using javascript and ajax to call server side mothod.  The pagemethod can only be static function in teh server side.  But i know static methods are not thread safe across simultaneous sessions.  However, what if the static method is modifying a non-static object?

for example:

public partial class default : system.web.ui.page

Hero Superman; // create an object called superman of class hero for all user sessions independently

public static int(newpowers)


Superman.powers = newpowers;  // Is this thread safe?  Will each user not accidentally get written by another user's power values?


web service thread-safe?



I am using a COPY web service. Is the function that uploads a document, COPYINTOITEMS, a thread-safe? If not, what is a good way to do a similar thing?

I am thinking to create one copy object and all incoming requests(thread) share this object to invoke CopyIntoItems function.

Thank you.

Is Dispatcher.BeginInvoke really NOT thread safe, while the old System.Windows.Forms.Control.BeginIn




System.Windows.Forms.Control.BeginInvoke is documented as thread safe (in fact, BeginInvoke , EndInvoke , Invoke , InvokeRequired , and CreateGraphics are).



But in WPF, Dispatcher.BeginInvoke is not documented as thread safe. Which would appear to me as a regression (and not really convenient, to be honest).

Was it only forgotten in MSDN documentation, or should I really use external locking to prevent the dispatcher to get lost in its messages and priorities?



Thanks. ;)

Is XpathDocument thread safe?!? (FileShare.Read access?)


if you  have a private void function inside of main page of system.web.page.ui

            XPathNavigator nav;
            XPathDocument docNav;
            XPathNodeIterator NodeIter;
            docNav = new XPathDocument(@"D:\data\data.xml");
            nav = docNav.CreateNavigator();

and multiple users are now on the web application simultaneously using nav object, will it be thread safe?  In filestream, the solution was to use FileShare.Read parameter.  but does xpathdocument have something similar?


Writing to log file on first pageload (!ispostback). thread safe


Based on this piece of code, I want to do exactly like this demonstration.  However, correct me if I'm wrong but if two or more users somehow simultaneously access the web page at the same precise nanosecond in time, then wouldn't we have a race condition?  So is this piece of code valid?  How would I correct this to make it thread safe???

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How to track visitors to your site in ASP.NET & C#
Code to log the IP address & DNS name for visitors to each page
Posted on 4/3/2007 1:52:07 PM in #ASP.NET
[lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage] [lnkImage]   ASP.NET Social Bar? Get A Free one here!

Once you have published a site in ASP.NET, you'd like to know who are your visitors. One way is to check your event log on the host server. Another option is to write your own code. You'd basically like to log the IP address, and DNS name for the visitor, and it would be nice to know which page they are visiting.

To log the ip address using ASP.NET, you can call:


Another usefull variable is


ChannelFactory / thread safe?


Is ChannelFactory<T>.CreateChannel thread safe in .NET 4.0?  Would like to use as a singleton dependency via castle windsor.





Is AcceptAsync on Socket is Thread Safe?


Hi ,


I am using the Asynchronous methods of the Socket class to Socket Communication. I would like to know whether the Usage of AcceptAsync is thread safe , ie I need to handle large number of connections at a time and cannot spend much time in handling a connection , hence  I am calling AcceptAsync in a loop initially (say 100 iterations ) using differnt SocketAsyncArgs Object,

and in the Event handler for SocketSyncEventRgs Completed Event , I am queing the just established connection to a threadpool thread for further execution (by passing the AcceptSocket of the SocketAsuncArgs)and then again calls AcceptAsync  on the main socket with a new SocketAsyncEventArgs object .

ie Intial AcceptAsync in  a loop and each time a connection established just after queing that connection to another threadpool thread, again calling AcceptAsync on the Main listening socket , So there is a chance that multiple threads will call AcceptAsync on the same Main Listening Socket and but with different SocketAsyncArgs Object , Is there any risk in this ?








Tooltip for GridView Column Headers (ASP.Net)

I just wanted to add auto tooltips for my GridView headers. There are couple of ways but I don't want to use javascript and wanted to use simple 'title' attribute. It took couple of hours to get the working code supporting sortable columns. I thought it will be very useful for others. Here's the code and logic behind it.

Multiple Column Dropdownlist for the ASP.NET DataGrid

Based on my previous control "Multiple Column DropDownList for ASP.NET", I received many emails asking for the same control to be used in the DataGrid for web applications. Here we go.. This control can be used as the regular MS DropDownList in the DataGrid and also as a regular dropdownlist. It has all the properties, like DataTextField, DataValueField, DataSource, SelectedIndex etc. The download file contains the samples both in VB.NET and C#. In this sample, I have used the Northwind database of SQL Server.

Alternating row background for first column of a report


is there a way to make the first column of a report use the an alternating background color? 

I have the background color set for the entire row however it does not work for the first column if the color is set to an expression.  If I just set it to a color i.e. red it works just fine. If I insert a dummy column to the left it works just fine (but the dummy column does not work, presumably because it is first??).

In the file below only the textbox for part number does not show an alternating background.  All others work correctly.

                    <Textbox Name="PartNumber">

Use a column as parameter for a sds in another column; gridview


Hola, I have a gridview which is bound to a sds which returns 7 columns and I added two columns from the GUI.  What I want is to fill up the 9th column with DDLs and these  DDLS will get their data from a different sds which is using a stored procedure with a single parameter.  I created the 9th row, used template field, made the sds for 9th row, the stored_procedure, threw a DDL in Item template and all  I need now is to pass a parameter in the first column to the sds in the 9th column.  I can code this but i'm getting tired of aspx.cs :) and would like to do it from the GUI.

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