The method that allows to add methods to existing type without creating a new derived type, recompiling, or otherwise modifying the original type.

A method signature template with a return value and an argument

public static <T_RETURN> <METHOD_NAME>(this <T_TYPE> <VAR_NAME>, <T_ARG1_TYPE> <ARG1_NAME>)

This method is actually a static method but the first argument has the keyword this and the target type to extend. Also it holds the instance of the target type.

The T_RETURN and the argument part of the template are optional. Also the argument is not limited to just one, you can have as many as required by your extension.

Description

A member of a class that provides flexibility for exposing private fields.

Sample Property Declaration

//backing private field
private string prop;

public string ReadWriteProp {
    get {
        return prop;
    }
    set {
        prop = value;
    }
}

public string ReadOnlyProp {
    get {
        return prop;
    }
}

public string WriteOnlyProp {
    set {
        prop = value;
    }
}

Sample Auto-Implemented Property Declaration

A more concise property declaration especially if theres no additional logic required for the accessors.

public string ReadWriteProp {
    get; set;
} 

public string ReadOnlyProp {
    get; private set;
} 

public string WriteOnlyProp {
    private get; set;
}

Definition

Delegate is a type that references methods with a particular parameter list and return type.

Printer Custom Delegate

public delegate void Printer<T>(T data);

A Method for Printer Delegate

static void ConsoleWrite<T>(T data) {
    Console.WriteLine(data);
}

Reference the ConsoleWrite method with Printer delegate

Printer<String> consoleOut = new Printer<String>(ConsoleWrite);
consoleOut("test");

Usage

The virtual keyword allows to modify a method, property, indexer or event declaration and to be overridden in a derived class.

Example

public virtual double volume() {
   return len * width * height
}

Description

These are delegates built-in with the framework and ready for your use.

List of Generic Delegates

A double quoted string prefixed with an at (@) sign symbol will be interpreted verbatim.

Syntax

@"<STRING>"

The STRING token can have simple escaped sequences (e.g. \\ for backslash), hexadecimal escape sequence (i.e. \x<HEX_NUMBER>) and unicode escape sequences (i.e. \u<HEX_NUMBER>) that are interpreted literally. However, the "" will still be escaped an will produce a single double quote mark.

Verbatim string literal and string interpolation can be combined with the syntax as $@"<STRING>". Moreover, the {{ or }} will still be escaped.

Example

var string1 = "C:\\Windows\\System32"
var string2 = @"C:\Windows\System32"

Console.WriteLine(string1)
Console.WriteLine(string2)

The writelines will produce the same output.

A double quoted string prefixed with a dollar ($) sign symbol can includes interpolation expression.

Syntax

$"<STRING>"

The STRING token can have interpolation expression and has the following syntax:

{<INTERPOLATION_EXPRESSION>[,<ALIGNMENT>][:<FORMAT_STRING>]}

If you needed to include { or } in your string output, escape it as {{ or }} respectively on which ever you need.

Example

var name = "World"
var greeting = $"Hello {name}"