#language integrated query

New Post has been published on http://www.varindersandhu.in/2011/09/20/asp-net-introducing-linq-data-providers/

ASP.Net - Introducing LINQ Data Providers

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The LINQ language extensions allow you to query data in a consistent manner. However, LINQ also includes additions to the .NET Framework itself for working with specific types of data such as relational databases, XML, and objects.These additions allow you to connect to this data, query against it, and insert, update, and delete items within the data all by using strongly typed objects. The following lists the core data types ( LINQ Data Providers )LINQ supports in the .NET Framework:

LINQ to SQL This addition allows you to connect to a SQL database and query data.You can create an object model to represent your database. You can then use LINQ to insert, update, and delete records as well as query this strongly typed object model.

LINQ to DataSet This addition allows you to query against an in-memory, ADO.NET DataSet object. You can use the power of LINQ along with the ubiquity of DataSet objects to simplify working with cached data.

LINQ to Entities This addition allows you to write queries against data modeled by using the Entity Framework (EF). The EF is a conceptual model of a database that typically involves an object-to-database mapping layer. LINQ to Entities allows you to query against this object layer by using the power of LINQ.

LIN Q to XML This addition provides a LINQ-based interface for working with XML data structures. You can use LINQ to XML to create XML, load an XML file, query XML data, manipulate the XML, and transform the XML into another shape.

LINQ to Objects This is the base level of LINQ programming. With LINQ to Objects, you are not writing queries by using an intermediate LINQ provider (such as LINQ to SQL or LINQ to XML). Instead, LINQ to Objects is simply the term for querying directly against any collection that implements the IEnumerable or IEnumerable<T> interface. Possible collections of this kind include List<T>, Array, Dictionary<TKey, TValue>, or even a string array.

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New Post has been published on http://www.varindersandhu.in/2011/09/19/asp-net-introducing-linq/

ASP.Net - Introducing LINQ

LINQ stands on Language Integrated Query. LINQ changes the way you access and query data. Before LINQ was created, most queries were expressed as text that was executed against a database. This SQL text was often specific to the underlying technology of the database being queried. LINQ elevates the process of querying for data to actual language constructs and keywords. This has two primary advantages: First, it provides type checking of your query code at compile time; this means that you are likely to encounter fewer errors, you can use IntelliSense, and it will be easier to write code. Second, it provides a consistent model for querying against all database technologies and all data, including lists, XML, arrays, database tables, and more.

LINQ and IEnumerable

LINQ queries introduce several contracts and keywords to Visual Basic and C#. These keywords allow you to write queries against anything that supports the base interface, IEnumerable or IEnumerable<T>. In the .NET Framework, this means nearly all collections of data, including DataSet, List<T>, Array, and many more. For example, assuming that you have a list of Employee objects named employees, the following LINQ query code would return all employees working in the IT department from that list.

Example in Visual Basic

Dim empQuery As IEnumerable(Of Employee) = From emp In employees Where emp.Department = "IT Department" Select emp

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Example in C#

IEnumerable<Employee> empQuery = from emp in employees where emp.Department == "IT Department" select emp;

Notice that the LINQ query is actually saved to a typed variable, in this case IEnumerable<Employee>. You can save your query to what are called queryable types. The common ones are IEnumerable<T> and IQueryable<T>. These allow the query to actually automatically examine (“iterate over”) each piece of data when executed. You can skip using this typed syntax and simply use the var keyword in C# or no type value in Visual Basic to declare your query variable. The following shows an example.

Example in Visual Basic

Dim empQuery = From emp In employees Where (emp.Department = "IT Department") Select emp

Example in C#

We all know that whenever possible we code should be written to be type safe. But there are times when its simply not possible. Once such time we came across when putting together the Mvpc libraries behind the Ambidect Technology involved working with…