METHODS in Visual C#

Encode Data Matrix ECC200 in Visual C# METHODS

Method bodies can have other blocks nested inside them. There can be any number of blocks, and they can be sequential or nested further. Blocks can be nested to any level. Local variables can be declared inside nested blocks, and like all local variables, their lifetimes and visibility are limited to the block in which they re declared and the blocks nested within it.

Figure 5-3 illustrates the lifetimes of two local variables, showing the code and the state of the stack. The arrows indicate the line that has just been executed. Variable var1 is declared in the body of the method, before the nested block. Variable var2 is declared inside the nested block. It exists from the time it s declared, until the end of the block in which it was declared. When control passes out of the nested block, its local variables are popped from the stack.

Note In C and C++ you can declare a local variable, and then within a nested block you can declare another local variable with the same name. The inner name masks the outer name while within the inner scope. In C#, however, you cannot declare another local variable with the same name within the scope of the first name regardless of the level of nesting.

A local constant is much like a local variable, except that once it is initialized, its value can t be changed. Like a local variable, a local constant must be declared inside a block. The two most important characteristics of a constant are the following: A constant must be initialized at its declaration. A constant cannot be changed after its declaration.

The core declaration for a constant is shown following. The syntax is the same as that of a field or variable declaration, except for the following: The addition of the keyword const before the type. The mandatory initializer. The initializer value must be determinable at compile time and is usually one of the predefined simple types or an expression made up of them. It can also be the null reference, but it cannot be a reference to an object, because references to objects are determined at run time.

Note The keyword const is not a modifier but part of the core declaration. It must be placed immediately before the type.

Keyword const Type Identifier = Value; Initializer required A local constant, like a local variable, is declared in a method body or code block, and it goes out of scope at the end of the block in which it is declared. For example, in the following code, local constant PI goes out of scope at the end of method DisplayRadii. void DisplayRadii() { const double PI = 3.1416;

for (int radius = 1; radius <= 5; radius++) { double area = radius * radius * PI; // Read from local constant Console.WriteLine ("Radius: {0}, Area: {1}" radius, area); } }

Methods contain most of the code for the actions that comprise a program. The remainder is in other function members, such as properties and operators but the bulk is in methods. The term flow of control refers to the flow of execution through your program. By default, program execution moves sequentially from one statement to the next. The control statements allow you to modify the order of execution. In this section, I ll just mention some of the available control statements you can use in your code. 9 covers them in detail. Selection statements: These statements allow you to select which statement, or block of statements, to execute. if: Conditional execution of a statement if...else: Conditional execution of one statement or another switch: Conditional execution of one statement from a set

Iteration statements: These statements allow you to loop, or iterate, on a block of statements. for: Loop testing at the top while: Loop testing at the top do: Loop testing at the bottom foreach: Execute once for each member of a set

Jump statements: These statements allow you to jump from one place in the block or method to another. break: Exit the current loop. continue: Go to the bottom of the current loop. goto: Go to a named statement. return: Return execution to the calling method.

For example, the following method shows two of the flow-of-control statements. Don t worry about the details. void SomeMethod() { int intVal = 3; Equality comparison operator if( intVal == 3 ) Console.WriteLine("Value is 3. "); for( int i=0; i<5; i++ ) Console.WriteLine("Value of i: {0}", i); }