Friday, February 6, 2009

Anonymous Types in LINQ : A Step Ahead Series


Programers of Visual Basic the keyword 'var' is confusing here as the type variants was used in Visual Basic.

Here, the keyword var tells to compiler emit a strong type based on t5e value of the operation on the right side.

Anonymous types can be used to initialize simple types like integers and strings.

Rules : Following are the some basic rules to use LINQ Anonymous Types.

  • Anonymous types can't be null.

  • Must always have an initial assignment.

  • Can be used with Simple or complex types, but composite anonymous types require member declaration

    var mylist = new {Topic="Anonymous-Types" [, declaratory = value, ...]}.

    in above Topic is the member declaratory.

  • Supports intelliSense.

  • Cannot be used for class field.

  • Can be used with arrays.

  • Anonymous types are all derived from the Object type.

Now, lets explore some category or types of anonymous types:

Simple Anonymous Type

With the keyword var and giving the value of the variable in the right side of the assignment operator (=), anyone can declare the Simple anonymous type.

var list = "Anonymous Types in LINQ : A Step Ahead Series";

The anonymous type is assigned to the name on the left side of the assignment operator, and the type emitted by the compiler to Microsoft Intermediate Language (MSIL) is determined by the right side of the operator.

The above line is identical in the MSIL if defined as following:

var list = "Anonymous Types in LINQ : A Step Ahead Series";

Array Initializer Syntax

Anyone can use the Anonymous Type to initialize the array too but with a rigid rule that is : new keyword must have to use.


var myArrayWithAntype = new int[]{ 1, 2, 12, 53, 58, 8, 2113, 2221 };

In above the array is Anonymous as it is defined with Annonymous Type initialize rule.

Composite Anonymous Types : Lets define

Now, lets take a look how to define Composite Anonymous Type. Its called just as class without the "typed" class definition.

var fullname = new {FirstName=”Gaurav”, LastName=”Arora”};

in above 'fullname' contains both first and last name. Go through following:

//throws an error

//Displays fullname

Note :
1. Anonymous types are immutable.
2. Within the scope of article we have supplied a little tricks, there can be generic anonymous methods, you can apply methods, can return anonymous values etc.

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