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In the following example, each instance of the Color class has a separate copy of the r, g, and b instance fields, but there is only one copy of the Black, White, Red, Green, and Blue static fields:

public class Color { public static readonly Color Black = new Color(0, 0, 0); public static readonly Color White = new Color(255, 255, 255); public static readonly Color Red = new Color(255, 0, 0); public static readonly Color Green = new Color(0, 255, 0); public static readonly Color Blue = new Color(0, 0, 255);

private byte r, g, b;

public Color(byte r, byte g, byte b) { this.r = r; this.g = g; this.b = b; } }

As shown in the previous example, read-only fields may be declared with a readonly modifier. Assignment to a readonly field can only occur as part of the field’s declaration or in an instance constructor or static constructor in the same class.

1.6.5 Methods

A method is a member that implements a computation or action that can be performed by an object or class. Static methods are accessed through the class. Instance methods are accessed through instances of the class.

Methods have a (possibly empty) list of parameters, which represent values or variable references passed to the method, and a return type, which specifies the type of the value computed and returned by the method. A method’s return type is void if it does not return a value.

The signature of a method must be unique in the class in which the method is declared. The signature of a method consists of the name of the method and the number, modifiers, and types of its parameters. The signature of a method does not include the return type. Parameters

Parameters are used to pass values or variable references to methods. The parameters of a method get their actual values from the arguments that are specified when the method is invoked. There are four kinds of parameters: value parameters, reference parameters, output parameters, and parameter arrays.

A value parameter is used for input parameter passing. A value parameter corresponds to a local variable that gets its initial value from the argument that was passed for the parameter. Modifications to a value parameter do not affect the argument that was passed for the parameter.

A reference parameter is used for both input and output parameter passing. The argument passed for a reference parameter must be a variable, and during execution of the method, the reference parameter represents the same storage location as the argument variable. A reference parameter is declared with the ref modifier. The following example shows the use of ref parameters.

using System;

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