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<TD class=content>1。4 预定义类型(Predefined types) d% E; R$ B6 X: s! u2 l4 q. p3 }
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c#提供了一系列预定义类型。它们与c/c++有不少相似的地方。预定义引用类型有object和string。 7 T1 s7 O! Z$ j' g
object类型是所有其他类型的基础。 ) N% ~3 O: r8 K( p4 w9 T5 | 1 e- m9 ~5 M/ l1 R预定义类型包括符号数、无符号数、浮点、布尔、字符和十进制数。符号数有:sbyte、short、 % R. |( l6 ?& O" G
int和long;无符号数有:byte、ushort、uint和ulong;浮点数有:float和double。 1 k f: J& ?+ Y+ h' Y8 p& r' h
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布尔类型就像一个开关,只有两种状态:true或false。c#对布尔的要求比c/c++严格,与java类似。 ( h( x/ O4 p/ ^4 m3 x. F
在c#中false不等于0,true也不等于1;false和true都是单独分离出来的一个值。学过c/c++的网友 7 R9 k/ J) C* T5 o" s
都知道:*/ 2 i8 w" l9 g4 t* G- [4 l
int i = 0; 2 [ w% x1 C* c5 q& O
if (i = 0) { // Bug: 应该是 (i == 0) : M8 O5 g% x _1 c
.... 7 O! g% W3 k( W6 L$ j* `7 T
} ( g6 a3 b! c# D$ g: M/ d/* 是没有问题的。但在c#中会引发一个编译错误(error CS0029: Cannot implicitly convert 0 w, [+ S! J/ N3 J& `9 T' ^- Z+ u
type 'int' to 'bool')。当然,这样牺牲了一点没有必要的灵活性。我们再也不能这样:*/ ! q1 [1 R p9 g% d" \string str; G6 g" V5 ?3 \' b3 ~$ M.... + ~+ P; U. c* i/ ?+ ^! J+ n! m6 _
if(str = Console.ReadLine()) { + r5 s8 d" ^& `$ V1 A* I
Console.WriteLine("Your comments are: {0}",str); 7 @ s' E( J4 C. o2 F) s6 m4 Z) w.... # l# B. V7 o$ r% `* r) d/* 而必须:*/ 0 D- j- c7 M% Y# ` `3 z0 B/ R
using System; $ v5 R2 J9 d, ^
class BoolTest 9 X g0 P% h, S9 k( S{ $ p4 A. I# ]1 v; M/ @; k5 `0 M
static void Main() { & O/ \) v; v4 i string str = Console.ReadLine();//也可以:string str; : H8 k- q W( w
if(str == "") // if((str = Console.ReadLine()) == "") : P- g# x0 Q, D' z& V
Console.WriteLine("i can't read your comments. Please tell me something! O.K.?"); 0 l% ?4 o' J7 c3 C! _. r
else $ N+ @/ ~5 [, I" I; b
Console.WriteLine("Your comments are: {0}",str); # F/ `5 }. ^- n0 W
} # f1 q! d/ Q! c2 ]* [; a} + \* m0 s. a" n
/* 2 \) y3 T" J1 W) \! j' f我抄了一张预定义类型的简表供大家参考。 % U1 _ h: g& M9 h 6 S: ]7 @0 K% o7 x& y4 WType Description Examples ; \9 ?7 {9 s, K5 E& D- J: A2 p. r : }1 G+ S& c5 M! tobject The ultimate base type of all other types object o = new Stack(); 7 S- ]. Z$ q; V
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string String type; a string is a sequence of string s = "Hello"; 7 m0 d$ l Q i' w1 C Unicode characters ; H8 c0 _/ y! r g6 ^
& f) o. _9 ]! y% Ksbyte 8-bit signed integral type sbyte val = 12; % X' m0 r" {& a6 T
/ ]1 k8 K5 H" E+ X I: Rshort 16-bit signed integral type short val = 12; : N' s) w. n/ @6 u% M/ I: T
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int 32-bit signed integral type int val = 12; 9 ]1 T. D$ d/ p$ D8 t; r/ Z 2 ?& O$ W; {" Y6 P/ s2 Vlong 64-bit signed integral type long val1 = 12; 6 |& l! a* A! Y/ I0 _. k" M$ j* F long val2 = 34L; / Y+ J! C b) t/ B }" G
/ e, q4 l' {# G6 x- k& c0 \8 N' Pbyte 8-bit unsigned integral type byte val1 = 12; 4 [3 Y% l6 l4 B8 G( n' C byte val2 = 34U; - ?% Z1 D0 A4 L. k5 g1 u+ s ; p0 X0 D8 f/ u# \' {0 N: g- jushort 16-bit unsigned integral type ushort val1 = 12; # y% S9 b' v0 s; S; F0 `* S% K7 \ ushort val2 = 34U; 5 G! h' w/ o6 J$ `
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uint 32-bit unsigned integral type uint val1 = 12; " x, {- p5 ]$ n) A2 s5 q! ]* c3 [ uint val2 = 34U; : A+ _8 c# }0 F4 ^3 G. J- T3 K$ ~ ^; m- ?: W& I" B4 x j; aulong 64-bit unsigned integral type ulong val1 = 12; h/ O6 J$ x# ~- F9 m ulong val2 = 34U; ) ~* C1 Y5 H' L
ulong val3 = 56L; ; a9 l' Q/ q" M7 H; V
ulong val4 = 78UL; + v* A3 [$ @( ?) F( m
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float Single-precision floating point type float value = 1.23F; * z1 n. I, G7 N) H( U( U# V. w o( A2 [# ^; g$ M E' u% M
double Double-precision floating point type double val1 = 1.23 & R5 L. y# j+ w" c) e
double val2 = 4.56D; * e$ R4 O+ }$ a y C- B# d0 w# s/ |, p7 K
bool Boolean type; a bool value is either bool value = true; ) j$ }3 ~: W! j: b8 c' F+ s
true or false * j. q% _* g7 s
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char Character type; a char value is a Unicode char value = 'h'; 4 o! G0 {) n0 n* d6 b$ Z character ! e! I2 R* }8 m! P; R6 N" M' A q / k! m8 s+ c! Q1 q; Cdecimal Precise decimal type with 28 significant digits decimal value = 1.23M; 7 K8 ^/ ]0 S& D# ]5 k" g- K5 K # E% F* ~ O6 I$ r! e你也可以自定义自己的预定义类型,可以这样:*/ $ B4 m0 A1 d; X
using System; & V( u% E5 @% u; ]( W+ L
struct Digit & m. T5 T" B- ^# B r: v
{...} 5 [- ~5 q6 B) N' g) mclass Test ( B. e; _ D" j- Z; X) |
{ : U" R |4 t9 X( {% }! G! f* ?. n static void TestInt() { ; n8 H" @* o. W. S4 B; h int a = 1; , M. R# f8 e1 k: p- F int b = 2; 9 W5 V1 y: s1 \) T int c = a + b; , s/ O2 d' z2 {8 k, H% _) a+ A2 A
Console.WriteLine(c); 6 z& W' O6 v9 y } % X! O E; b, K0 v* G& e
static void TestDigit() { 3 x, j$ }) V& | Digit a = (Digit) 1; 6 w/ s$ o% _8 R( ~. u) B2 ^ Digit b = (Digit) 2; 2 Z; D" Z1 L5 c% l2 L, J7 P" c
Digit c = a + b; 9 H6 l, e/ J3 x: @% I& B( T Console.WriteLine(c); ' r3 P/ x; K" c' T; X
} % k# b$ B6 {2 |& {7 a8 H4 D
static void Main() { % Q) Z2 H9 I) m- ]9 X+ D
TestInt(); ) x- [' H3 A9 X: t
TestDigit(); * q- R$ t) s( R0 ?* r
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/* $ J; J" ?& K* A
这一节有点沉闷。:( $ r: B- t; {* t# x9 \, p, f' \' h0 E6 W2 L5 [+ c% ~% l8 @
<IMG> <IMG> <IMG> ; v" r& l- a9 \" E* }) n<FONT color=#568ac2></FONT>7 ~8 |1 [) t0 t' U1 W* T
<FONT color=#ff8080></FONT></TD></TR></TABLE></TD></TR>; ~) n3 f, R4 H# @& G) N+ Y
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<TD class=t1 noWrap>作者:<a href="http://search.tencent.com/cgi-bin/friend/user_show_info?ln=5151599" target="_blank" ><IMG><FONT color=#000000> Burn[5151599]</FONT></A> 2000-10-26 09:55:02 </TD>: T2 v; v8 p3 d1 Z& K
<TD noWrap align=right width="25%"><a href="http://bbs.tencent.com/cgi-bin/bbs/bbs_post?type=r&messtype=r&back=1&groupid=102:10047&messageid=145139&begnum=0&bbegnum=50&mmessageid=263511&st=&sc=&club=" target="_blank" ><FONT color=#000000>[回复]</FONT></A> </TD></TR></TABLE>. y: L% h9 a/ i1 _% Q& V: v# s3 m; L
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<TD class=content>呵呵,我又是第一个了,呵呵,那个王先生呢! ' F3 m. A) @/ R9 C4 t
兄弟再来,我喜欢看。 7 A1 [8 ~+ j$ | r2 ~" d, \& x8 _' g* t8 U
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<FONT color=#568ac2>我是个盖世英雄,有一天我会驾着七彩降云杀入敌营去救我的情人,我猜对了前头 - z: P! F/ x0 {5 N也猜对了这结果。(Zzzz....) 6 P3 L9 J0 l; \6 L" H; i; g+ g</FONT>/ o- @6 x1 m/ P: C1 u
<FONT color=#ff8080></FONT></TD></TR></TABLE></TD></TR>; G6 X) a2 K- B. T: E1 r
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<TD class=t1 noWrap>作者:<a href="http://search.tencent.com/cgi-bin/friend/user_show_info?ln=21847847" target="_blank" ><IMG><FONT color=#000000> 王志清[21847847]</FONT></A> 2000-10-27 21:26:28 </TD> * Z" c/ W- [/ ]3 R<TD noWrap align=right width="25%"><a href="http://bbs.tencent.com/cgi-bin/bbs/bbs_post?type=r&messtype=r&back=1&groupid=102:10047&messageid=145139&begnum=0&bbegnum=50&mmessageid=263575&st=&sc=&club=" target="_blank" ><FONT color=#000000>[回复]</FONT></A> </TD></TR></TABLE>( S" ? Z! P8 P- L" A9 B" e
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<TD class=content>兄弟今天来的是晚了一点,真是抱歉之极! 5 B: M- \+ _% W3 _9 R0 W
只好坐后面一点,认真听课了……5 _, }& _% p. a _, K/ g# P