Challenge
Almost every application uses data in some form, whether the data comes from in memory, databases, XML files, or text files. Many developers find it difficult to switch from strongly typed object-oriented programming to the data access tier in an application. In C#, developers can navigate easily through the namespaces, work with a debugger in the Visual Studio IDE, and more. However, when accessing data, you will notice that things are quite different and more tedious. Developers end up in a world that is not strongly typed, where debugging is a pain or even non existent, and lots of time is spent sending strings to the database as commands. The goal for LINQ was to provide a methodology that simplifies and unifies the implementation of accessing any kind of data. It makes it easier to interact with SQL, relational databases, XML, and the programming languages that communicate with them. LINQ does not force you to use a specific architecture, but facilitates the implementation of several existing architectures for accessing data. Some examples include RAD/prototype, Client/server, N-tier, and Smart client.
Solution
LINQ stands for Language-Integrated Query and covers a set of features that lets you retrieve information from a data source. In many cases, data is stored in a database that is separate from the application. Traditionally, interacting with a relational database would involve generating queries using SQL (Structured Query Language). Other sources of data, such as XML, would require their own approaches that were completely different. However, LINQ gives C# the ability to generate queries for any LINQ-compatible data source. Furthermore, the syntax used for the query is the same, no matter what data source is used. Accessing a relational database is the same as data stored in an array, and the query capability is fully integrated into the C# language. LINQ in C# is essentially a language within a language and as a result, the subject of LINQ is quite large, involving many features, options, and alternatives. It contains set of standard query operators that provide the underlying query architecture for the navigation, filtering, and execution operations of nearly every kind of data source. LINQ also provides the means for developers to stay within the coding environment that they comfortable with and access the underlying data as objects that work with the IDE, IntelliSense, and even debugging. These aspects, combined with shorter, more meaningful, and expressive syntax boosts developer productivity.
Benefit
LINQ is a lightweight disguise over programmatic data integration. It hardly matters what you are querying against, because queries will be quite similar using a whole new set of procedures and keywords. It gives developers a simplified way to write queries by using a unified query syntax to use regardless of the source of data. It promotes faster development time by removing run-time errors and catching errors at compile time. LINQ is fully integrated with IntelliSense, and supports debugging directly in the development language. Using LINQ, you can query directly against your database and even against the stored procedures that your database exposes. The result of making these set operations, transforms, and constructs first-class operations is a set of methods called the standard query operators. These operators provide query capabilities that include sorting, filtering, aggregation, and projection over a large number of different data sources. LINQ-compatible data sources include LINQ to Objects, LINQ to ADO.NET, LINQ to SQL, LINQ to XML, LINQ to DataSet, and LINQ to Entities. By being able to use LINQ to Objects, C# arrays and collections are treated like databases. This gives developers extensive flexibility and an easy way to query data in the collections. LINQ can be extended to support other data sources such as LINQ to SharePoint, LINQ to Exchange, and LINQ to LDAP. By using LINQ, developers can now enjoy the benefits of a single declarative pattern that can be expressed in any .NET-based programming language, and closes the gap between relational data and object-oriented development.
