Saturday, December 26, 2009

LINQ for dummies - an overview


Why do we need LINQ?

Most of us would have wrote code to access data from different data sources a database, in memory objects , XML files or from other formats. We have different guidelines, architectures and methods to process and retrieve these data collection. For a data control in form it is immaterial whether the data is from XML or any other data sources. We have many relational OO databases but there always the gap between the data and its processing in Objects in any modern languages.


Is LINQ the Holy Grail?
I can’t decide on that. But LINQ tries to fill the vacuum between the datasources and their successful interpretation in Objects. With LINQ, Microsoft’s intention was to provide a solution for the problem of object-relational mapping, as well as to simplify the interaction between objects and data sources. LINQ eventually evolved into a general-purpose language-integrated querying toolset. This toolset can be used to access data coming from in-memory objects (LINQ to Objects), databases (LINQ to SQL), XML
documents (LINQ to XML), a file-system, or any other source.

LINQ can be used to access any type of object or datasource. The syntax remains the same. Previously we had to use different methods like ADO.Net.  XPath, IO packages etc to retrieve data ( ok still we can use these methods and in many cases I still prefer them over LINQ)

Broadly classifying we have three major categories of LINQ
  1. LINQ to Objects,
  2. LINQ to SQL,
  3. LINQ to XML

Don’t worry there are other categories like LINQ to datasets. LINQ to Entities ( with ADO.net entity framework). In Visual Studio you can write LINQ queries in Visual Basic or C# with SQL Server databases, XML documents, ADO.NET Datasets, and any collection of objects that supports IEnumerable or the generic IEnumerable(T) interface. In short .NET Language-Integrated Query defines a set of general purpose standard query operators that allow traversal, filter, and projection operations to be expressed in a direct yet declarative way in any .NET-based programming language. Third parties are also free to replace the standard query operators with their own implementations that provide additional services such as remote evaluation, query translation, optimization, and so on. By adhering to the conventions of the LINQ pattern, such implementations enjoy the same language integration and tool support as the standard query operators.

Next – LINQ in action ... 
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