Whats New In C# 3.0

Here is a point wise summary of features introduced newly in C# 3.0 Implicitly Typed Local Variables •

Local variables can be declared as type ‘var’ which means compiler to determine the actual type based on the data by which its is initialized.

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var i = 10; // i is created of type int

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var name = “MyName” ; // name is created of type string

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can only be used when declared and initialized in same statement.

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Cannot be initialized to null.

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Cannot be used as class members.

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Mostly used to store anonymous types as in LINQ based programming.

Object & Collection Initializers •

Allow assigning values to any accessible members or properties of a type at the time of initiation without invoking the constructor with parameters.

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The default constructor gets executed before assigning the values.

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E.g. Coordinate c1 = new Coordinate {x=1 , y=2};

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Used in LINQ query expressions along with anonymous types.

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Collection Initializers use Object Initializers to specify multiple elements of collection without calling Add method multiple times.

Extension Methods •

Allows adding new methods to existing types without modifying the existing type.

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Are special kind of static methods but are called as if they are instance methods.

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The first parameter passed to Extension methods specifies to which type they operate on preceded by ‘this’ keyword.

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They cannot access the private variables of type which they are extending.

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Extension Methods need to defined in a non-nested and non-generic static class.

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Instance methods take priority over extension methods in case they have same signature.

Anonymous Types •

Are of class types which can have only public read-only properties as their members. No other class members like methods are allowed.

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They are of reference types and are derived from ‘Object’ class.

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Internally compiler gives them the name but its not accessible by application code.

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They have a method scope.

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Can be initiated directly e.g. new { property1=1, property2=”Hello World”};

Lambda Expressions •

Very similar to anonymous methods introduced in C# 2.0.

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Its an inline expression or statement block which can be used to pass arguments to method call or assign value to delegate.

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All lambda expression use lambda operator => where the left side denotes result and right contains statement block or expression.

Auto-Implemented Properties

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Helps in simplifying property declaration in cases where there is no custom logic required in accessors methods.

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E.g. public int Price {get; set;};

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Internally compiler creates an anonymous field for assigning values.