Visual C # getting started with programming

Program The activity is through Statement ( Statement ) . C # supports several different statements. Many statements are defined in the form of embedded statements. Block ) You can write multiple statements in the context where only one statement can be used. A block consists of a list of statements enclosed in braces. Statement (declaration statement) ) Declare local variables and constants. Expression Statement ( Expression statement ) Used for Operation expressions. The expression can be used as a statement to use 3, including method call, object allocation using the new operator, and assignment using the "=" and compound assignment operators, and the increment and decrement operations using the "++" and "--" operators.
Selection statement ) Used to select one of several possible statements based on the value of an expression. This group of statements includes if and switch statements.
Iteration statement ) Used to repeatedly execute embedded statements. This group of statements includes the while, do, for, and foreach statements. Jump Statement (jump statement ) It is used for transfer program control. This group of statements includes break, continue, Goto, throw, and return statements. The try-catch statement is used to capture exceptions that occur during block execution. In addition, the try-finally statement is used to specify a termination Code Block, whether an exception occurs or not, it is always executed. The checked and unchecked statements are used to control integer arithmetic operations and overflow checks of the conversion. The lock statement is used to obtain the mutex lock of a given object, execute the statement, and then release the lock. The Using statement is used to obtain a resource, execute a statement, and process the resource. Table 1.5 lists the C # statements and provides examples one by one. Table 1.5 C # statements

Sentence	Example
Local variable Declaration	Static void main () {int A; int B = 2, c = 3; A = 1; console. writeline (A + B + C );}
Local constant Declaration	Static void main () {const float Pi = 3.1415927f; const int r = 25; console. writeline (pI * r );}
Expression statement	Static void main () {int I; I = 123; // expression statement console. writeline (I); // expression statement I ++; // expression statement console. writeline (I); // expression statement}
If statement	Static void main (string [] ARGs) {If (ARGs. length = 0) {console. writeline ("no arguments");} else {console. writeline ("one or more arguments ");}}

(Continued table)

Sentence	Example
Switch statement	Static void main (string [] ARGs) {int n = args. length; Switch (n) {Case 0: console. writeline ("no arguments"); break; Case 1: console. writeline ("one argument"); break; default: console. writeline ("{0} arguments", n); break ;}}
While statement	Static void main (string [] ARGs) {int I = 0; while (I <args. Length) {console. writeline (ARGs [I]); I ++ ;}}
Do statement	Static void main () {string s; do {S = console. Readline (); If (s! = NULL) console. writeline (s);} while (s! = NULL );}
For statement	Static void main (string [] ARGs) {for (INT I = 0; I <args. length; I ++) {console. writeline (ARGs [I]);}
Foreach statement	Static void main (string [] ARGs) {foreach (string s in ARGs) {console. writeline (s );}}
Break statement	Static void main () {While (true) {string S = console. Readline (); If (S = NULL) break; console. writeline (s );}}
Continue statement	Static void main (string [] ARGs) {for (INT I = 0; I <args. length; I ++) {If (ARGs [I]. startswith ("/") continue; console. writeline (ARGs [I]);}
GOTO statement	Static void main (string [] ARGs) {int I = 0; goto check; Loop: Console. writeline (ARGs [I ++]); check: if (I <args. Length) goto loop ;}

(Continued table)

Sentence	Example
Return Statement	Static int add (int A, int B) {return a + B;} static void main () {console. writeline (add (1, 2); return ;}
Throw and try statements	Static double divide (Double X, Double Y) {If (y = 0) throw new dividebyzeroexception (); Return x/y;} static void main (string [] ARGs) {try {If (ARGs. length! = 2) {Throw new exception ("two numbers required");} Double X = double. parse (ARGs [0]); Double Y = double. parse (ARGs [1]); console. writeline (divide (x, y);} catch (exception e) {console. writeline (E. message );}}
Checked and unchecked statements	Static void main () {int I = int. maxvalue; checked {console. writeline (I + 1); // exception} unchecked {console. writeline (I + 1); // overflow }}
Lock statement	Class account {decimal balance; Public void withdraw (decimal amount) {lock (this) {If (amount> balance) {Throw new exception ("insufficient funds ");} balance-= amount ;}}}
Using statement	Static void main () {using (textwriter W = file. createtext ("test.txt") {W. writeline ("line one"); W. writeline ("line two"); W. writeline ("line three ");}}