C# 3.0 new features

This post is aimed to be a quick abstract for all the new C# language constructs introduced with the version 3.0.

Implicitly typed local variables

By using var keyword to define a local (does not work at class level) variable is not needed to define its type, the compiler will infer it.

Examples:

var i = 0;
var intArr = new[] { 0, 1, 2, 3 };

Object and Collection Initializers

Object’s properties can be initialized when creating the object and also the collection items.

Examples:

TextBox txt = new TextBox() { Text = "John", Width = 200 };

List<string> colorspaces = new List<string> {"RGB", "CMYK", "GreyScale", "B/W"};

Anonymous types

By combining the previous two features (Implicitly typed variables and Object initializers) you can create anonymous types (statically typed, with no name used in the code).

Example:

var guy = new { FirstName = "John", LastName = "Doe" };
Console.WriteLine(guy.FirstName);

Automatically Implemented Properties

You can create properties with no need for a private member to store its value.

Examples:

public string Name { get; set; }

//read-only property
public byte Age { get; private set; }

Extension methods

By using the this keyword in a static method argument you can extend another class. You "injects" methods to an existing class from another one.

Example:

public static class ExtensionClass
{
    //Extension method
    public static byte ToGray(this Color c)
    {
        return (byte)(0.3 * c.R + 0.59 * c.G + 0.11 * c.B);
    }
}

byte pixelGray = Color.Green.ToGray();

Lambda Expressions

Lambda expressions are like pretty simple functions that takes input parameters and evaluates an expression.

Syntax:

(input parameters) => expression

Examples:

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

int oddNumbers = numbers.Count(n => n % 2 == 1);

Console.WriteLine(oddNumbers.ToString());

Func<int, int> duplicate = number => number * 2;

Console.WriteLine(duplicate.Invoke(2).ToString());

Tags: C#