Have you ever worked with Microsoft Application Blocks, if yes then which?

The Application Blocks are C# & the VB.NET classes distributed as the Visual Studio projects which can be downloaded from the Microsoft's Website and used in any .NET application, including the ASP.NET Web applications. They are very useful and powerful tools that can make all applications more scalable, maintainable, and efficient.

Secondly which application blocks have been used totally depends on really what you have implemented. But there are 2 famous MAB which is making buzz around the industry:

1) Data access block:

The Data Access Block gives static methods located in the SqlHelper class which encapsulates the most common data access tasks performed with the Microsoft SQL server. If the term "static method" is new to you that mean that the class methods can be called without instantiating an instance of the class. For e.g., the method ExecuteReader () within the SqlHelper class can be called by using the statement SqlHelper.ExecuteReader () -- no object instantiation of the SqlHelper class is needed.

2) Exception management block:

The Exception Management Application Block gives a simple but extensible framework for handling the exceptions. With a single line of application code you can easily log exception information to the Event Log or extend it by generating your own components that log exception details to other data sources or notify the operators, without affecting your application code. The Exception Management Application Block can easily used as a building block in your own .NET application.