After you add a LINQ to SQL Classes item to a project and open the O/R Designer, the empty design surface represents an empty DataContext class ready to be configured. The DataContext class is a LINQ to SQL class that acts as a conduit between a SQL Server database and the LINQ to SQL entity classes mapped to that database. This class contains the connection string information and the methods for connecting to a database and manipulating the data in the database. It is configured with connection information provided by the first item that is dragged onto the design surface.

In Visual Basic, the basic syntax of a LINQ query starts with the From clause and ends with the Select or Group By clause. In addition, you can use the Where, Order By, and Order By Descending clauses to perform additional functions, such as filtering data and generating the data in a specific order.

In C#, the basic syntax of a LINQ query starts with the From clause and ends with the Select or group by clause. In addition, you can use the where, orderby, and Orderby descending clauses to perform additional functions, such as filtering data and generating the data in a specific order.

LINQ is a programming model that is the composition of general-purpose standard query operators that allow you to work with data, regardless of the data source in any .NET based programming language. It is the name given to a set of technologies based on the integration of query capabilities into any .NET language.

Variables that are defined in a C# program belong to two major categories: value type and reference type. The variables that are based on value type contain a value that is either allocated on a stack or allocated in-line in a structure. The variables that are based on reference types store the memory address of a variable, which in turn stores the value and are allocated on the heap. The variables that are based on value types have their own copy of data and therefore operations done on one variable do not affect other variables. The reference-type variables reflect the changes made in the referring variables.

You can deploy an ASP.NET Web application using either the Windows Installer deployment or ClickOnce deployment technique.

       => Windows Installer

       => ClickOnce

       => XCOPY

       => Copy Web Site

       => Publish Web Site tool

Workflows serve the purpose of automating business processes. Now, since each type of business has a wide range of problems; therefore, a workflow platform needs to be extensible. WF provides you with a set of base activities, such as IfElse, Code, and Delay, to build a workflow. You can extend these activities or build new activities to meet your requirements. Besides activities, you can also extend services, such as tracking, management, and persistence, provided by the runtime engine.

In WF 4.0, the following two types of workflows are used:

 
     Flowchart workflows - Helps you to create workflows using the common flowchart elements. In WF, the Flowchart activity is generally used to implement a non-sequential workflow, and occasionally it implements sequential workflows in case the FlowDecision nodes are not used. The Flowchart activity contains a collection of flow nodes, which inherit from the FlowNode class. The following types of nodes or elements can be a part of a flowchart:
                 => FlowStep - Executes activities of a flowchart in a sequence.
                 => FlowDecision - Shows the execution on the basis of a Boolean condition.   It is similar to the If construct.
                 => FlowSwitch - Shows the execution on the basis of an exclusive switch. It is similar to the Switch construct.


      Procedural workflows - Helps you to create workflows using basic and sequential execution standards. In WF, procedural workflows use flow control constructs, such as While, Switch, ForEach, and If, to execute activities. These flow control constructs are similar to those found in procedural languages. Procedural workflows can also contain other flow control activities, such as Flowchart and Sequence.