Skip to main content

ConcurrentBag<T> - Thread Safe Collections

.Net 4.0 introduces a new namespace, System.Collections.Concurrent, this namespace contains a set of collections that would be very much useful in threaded programming.
The Add or Remove methods of List<T> is not thread safe, meaning that if you are adding or removing items from a list which is accessed from multiple threads, you will end up overwriting some of the items.
So, in multi threading programming, you would need to lock the list before adding or removing items from it.

The ConcurrentBag<T&gt in the System.Collections.Concurrent is a thread safe collections i.e all you have to do is call Add or Remove in the usual way and the collection will take care of adding the items without overwriting them.

Here is an example using the ConcurrentBag<T&gt with the Parallel Task Library...

ConcurrentBag array = new ConcurrentBag();
try
{
Parallel.For(0, 100000, i =>
{
//Do some work here
array.Add(i);

});


}
catch (AggregateException e)
{
Console.WriteLine("\n\n\n\n");
foreach (Exception ex in e.InnerExceptions)
{
Console.WriteLine(ex.Message);
}

}

The ConcurrentBag resembles the List in that it is unordered and contain duplicate values and also accept a null as valid value for a reference type.

The System.Collection.Concurrent namespace also contains other implementation of thread safe collections, to name a few,ConcurrentStack, ConcurrentDictionary, ConcurrentQueue...

Comments

Popular posts from this blog

Hosting WCF services on IIS or Windows Services?

There came one of those questions from the client whether to use II7 hosting or windows service hosting for WCF services. I tried recollecting a few points and thought of writing it down. WCF applications can be hosted in 2 main ways - In a Windows service - On IIS 7 and above When WCF was first released, IIS 6 did not support hosting WCF applications that support Non-HTTP communication like Net.TCP or Net.MSMQ and developers had to rely on hosting these services on Windows Services. With the release of IIS 7, it was possible to deploy these Non-Http based applications also on IIS 7. Following are the benefits of using IIS 7 to host WCF applications Less development effort Hosting on Windows service, mandates the creating of a Windows service installer project on windows service and writing code to instantiate the service, whereas the service could just be hosted on IIS by creating an application on IIS, no further development is needed, just the service implementa...

The maximum nametable character count quota (16384) has been exceeded

Some of our services were growing and the other day it hit the quote, I could not update the service references, nor was I able to run the WCFTest client. An error is diplayed saying " The maximum nametable character count quota (16384) has been exceeded " The problem was with the mex endpoint, where the XML that was sent was too much for the client to handle, this can be fixed by do the following. Just paste the lines below within the configuration section of the devenve.exe.config and the svcutil.exe.config files found at the locations C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE , C:\Program Files\Microsoft SDKs\Windows\v6.0A\bin Restart IIS and you are done. The detailed error that you get is the following : Error: Cannot obtain Metadata from net.tcp://localhost:8731/ Services/SecurityManager/mex If this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. F...

Task based Asynchronous pattern, Async & Await and .NET 4.5

One of the key features in .Net 4.5 is to write asynchronous programs much easier. So if I was to write asynchronous programs in .Net 2.0/3.5, I would either follow the event based model or the callback based model. For an example, a synchronous method that does intensive work (say the DoWork()) can be made asynchronous by using the following patterns 1) Implementing the IAsyncResult pattern. in this implementation, 2 methods are exposed for the DoWork() synchronous method, the BeginDoWork() and the EndDoWork() method. The user will call the BeingDoWork() passing in the required parameters and a callback of the delegate type AsyncCallback(IAsyncResult). The BeginDoWork() will spawn a new thread a return control back to the user. Once work is completed in the spawned method, as a last step, it will call the inform the AsyncResult implementation, which in turns will call the EndDoWork() (which is the callback that was passed in to the BeginDoWork()). 2) Implementing the event pattern. ...