What is Thread Safe Collection?

People use to said that writing a collection which is mutable, thread safe and usable is an extremely difficult process. Since the .NET 4 introduce the system.collection.concurrent namespace, multiple threads can safely and efficiently add or remove items from these collection without requiring additional synchronization in user code. When you write new code, use the concurrent collection classes whenever the collection will be writing to multiple threads concurrently and in this article I’ll going to show you about thread safe collection in Concurent Queue.

Concurent in .Net

Concurrent collections in .NET work very much like their single-thread counterparts with the difference that they are thread safe. These collections can be used in scenarios where you need to share a collection between Tasks. They are typed and use a lightweight synchronisation mechanism to ensure that they are safe and fast to use in parallel programming.

Concurrent queues

The Queue of T generic collection has a thread-safe counterpart called ConcurrentQueue. Important methods:

1. Enqueue(T element): adds an item of type T to the collection
2. TryPeek(out T): tries to retrieve the next element from the collection without removing it. The value is set to the out parameter if the method succeeds. Otherwise it returns false.
3. TryDequeue(out T): tries to get the first element. It removes the item from the collection and sets the out parameter to the retrieved element. Otherwise the method returns false

The ‘try’ bit in the method names implies that your code needs to prepare for the event where the element could not be retrieved. If multiple threads retrieve elements from the same queue you cannot be sure what’s in there when a specific thread tries to read from it.

Example

Declare and fill a concurrent queue:

ConcurrentQueue<int> concurrentQueue = new ConcurrentQueue<int>(); 
for (int i = 0; i < 5000; i++)
{
    concurrentQueue.Enqueue(i);
}
We’ll want to get the items from this collection and check if all of them have been retrieved using a counter. The counter will also be shared among the threads using the ‘lock’ technique we saw in this post – or actually something that is similar to the ‘lock’ keyword: the Interlocked class. Interlocked has an Increment method which accepts a ref int parameter. It will increment the incoming integer in an atomic operation.

int itemCount = 0;
Task[] queueTasks = new Task[20];

for (int i = 0; i < queueTasks.Length; i++)
{
    queueTasks[i] = Task.Factory.StartNew(() =>
    {
        while (concurrentQueue.Count > 0)
        {
            int currentElement;
            bool success = concurrentQueue.TryDequeue(out currentElement);
            if (success)
            {
                Interlocked.Increment(ref itemCount);
           }
        }
    });
}

The while loop will ensure that we’ll try to de-queue the items as long as there’s something left in the collection.
Wait for the tasks and print the number of items processed – the counter should have the same value as the number of items in the queue:

Task.WaitAll(queueTasks);
Console.WriteLine("Counter: {0}", itemCount);

This Article will tell you how to faster loading of your ASP Pages and make the performance better, If you read the internet and all of the websites dedicated to Asp.Net you will inevitably read about the wonders of the DataGrid, DataList, and Repeater controls. While each of these has its place, if you are only displaying data there is a much faster and more efficient means to do so. Let's say you have a page that displays articles based on a query string. A normal asp page execution procedure goes like this. The code queries the database based on the Article I.D. and then brings back that information to the page where you display it in the fashion that you would like. This is a fairly straight forward approach with asp and is done all the time.

Check The Easy Step Below!

Use Asp.Net Caching

This is a no-brainer, and I won't go into the brilliance or details of asp.net caching here because at the time of this writing Google has 2,780,000 articles on the topic. Basically instead of querying the database each time the page is loaded you only query the database once and load that result into the system cache. Subsequent calls to load the page retrieve the data from the cache as opposed to the database which gives you an instant and considerable performance boost. You can then set the cache for how long the cache should store the information as well as many other features. If you are not using the cache, you should be whenever possible!

If possible, do NOT use the standard Asp.Net controls.

That's right. The standard asp.net controls are designed for rapid development and not page performance. They allow you to design pages that grab and display data very quickly but their actual performance suffers because of the extra overhead which is there for ease and speed of development time and not page execution speed.

Instead, create either a User Control or even better yet a Web Custom Control which is by far the fastest performance wise and really quite easy to create and use.

Use an SqlDataReader or even better yet use a set based command for Sql Server data retrieval and simply execute that one command against the database.

An asp.net SqlDataReader is a fast forward only datareader that closes the connection after it reads the last set of results. Now for my article pages we are only returning 1 particular result. In this case we would opt for the set based command. If you had more than 1 result returned, in your table of contents for instance, you would use the SqlDataReader because you are returning multiple sets of results.

Set based commands are stored procedures that bring back data through parameters as opposed to a result set which then in turn needs to be looped through to obtain your data. So instead of writing your stored procedure like the following which brings back 1 result set:

Select Title, Body, Author
From Articles
Where ArtID = 215

We can write it using a set based command like this.

Create Procedure mysp_GetArticle

@Title varchar(200) Output,
@Body varchar(8000) Output,
@Author varchar(500) Output

As

Select @Title = Title, @Body = Body, @Author = Author
From Articles
Where ArtID = 215

GO
The above query will return only the three parameters called for and not a result or record set so you
don't have to then walk through the returned record set that has only 1 result in it anyway. This second
little process of work decreases your performance so you should avoid it whenever possible. Combine
this technique with the asp.net cache

Use Classes and ArrayLists as opposed to returning an SqlDataReader.

Create a class and then if there are more than one set of results store those results into individual instantiations of that class. Finally store each of those classes into an ArrayList. You can then store only that ArrayList into the asp.net cache. So instead of getting the results back from a SqlDataReader when loading your page you get them from the ArrayList which is stored in the cache.

On the first time the page loads, query the database and return all of your data storing it into individual classes. Then store each of those classes into an ArrayList. If you only have one single result you may store only the class into the cache. Then take your ArrayList and store it into the cache.

Next create a Web Custom Control and pass the cached ArrayList to the custom control and loop out your data using the HtmlTextWriter which is very fast. Remember each subsequent call to load the page will be called from the cache which stores your ArraList of classes or your single class.

Certainly it takes a significant amount of additional coding to do it in this fashion, especially when you take proper error handling into consideration, but if you follow this approach your pages will be screeching fast, you will immediately notice the difference, and your asp.net pages will execute in the proper sequence - Data handling in the Page_Load function and the html display in the Page_Render function.