Section 72.7: Using static type

The using static [Namespace.Type] directive allows the importing of static members of types and enumeration values. Extension methods are imported as extension methods (from just one type), not into top-level scope.

Version ≥ 6.0

using static System.Console; using static System.ConsoleColor; using static System.Math;

class Program

{

static void Main()

{

BackgroundColor = DarkBlue; WriteLine(Sqrt(2));

}

}

Live Demo Fiddle

Version < 6.0

using System;

class Program

{

static void Main()

{

Console.BackgroundColor = ConsoleColor.DarkBlue; Console.WriteLine(Math.Sqrt(2));

}

}

Section 72.8: Index initializers

Index initializers make it possible to create and initialize objects with indexes at the same time.

This makes initializing Dictionaries very easy:

var dict = new Dictionary<string, int>()

{

["foo"] = 34, ["bar"] = 42

};

Any object that has an indexed getter or setter can be used with this syntax:

class Program

{

public class MyClassWithIndexer

{

public int this[string index]

{

set

{

Console.WriteLine($"Index: {index}, value: {value}");

}

}

}

Index: 10, value: Ten

Index: 42, value: Meaning of life

It should be noted that the indexer set accessor might behave di erently compared to an Add method (used in collection initializers).

For example:

var d = new Dictionary<string, int>

{

["foo"] = 34, ["foo"] = 42,

}; // does not throw, second value overwrites the first one

versus:

var d = new Dictionary<string, int>

{

{"foo", 34 },

{"foo", 42 },

}; // run-time ArgumentException: An item with the same key has already been added.

Section 72.9: Improved overload resolution

Following snippet shows an example of passing a method group (as opposed to a lambda) when a delegate is expected. Overload resolution will now resolve this instead of raising an ambiguous overload error due to the ability of C# 6 to check the return type of the method that was passed.

using System; public class Program

{

public static void Main()

{

Overloaded(DoSomething);

}

static void Overloaded(Action action)

{

Console.WriteLine("overload with action called");

}

static void Overloaded(Func<int> function)

{

Console.WriteLine("overload with Func<int> called");

}

static int DoSomething()

{

Console.WriteLine(0); return 0;

}

}

Results:

Version = 6.0