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<TD class=content>1。4 预定义类型(Predefined types) % ~4 z. P9 P5 _4 c. g" q v6 m/ c9 p. G+ q; b* V8 j" e
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。 ' S, S( ^( Y( m y% B. yobject类型是所有其他类型的基础。 & o. L* L, ?0 h
' z. n) B- _/ b- z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、 , d' a' [0 ?- q6 Z: S0 S
int和long;无符号数有:byte、ushort、uint和ulong;浮点数有:float和double。 ; y4 _& c* U; R" v7 c
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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。 / P) S5 v( U. M0 E* Q( m* W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 0 `4 e2 j$ R; r都知道:*/ ! F1 e5 J5 J- a$ m& k1 y" _2 Pint i = 0; ( t! X [# H+ T! C8 P" Y; |8 @$ S
if (i = 0) { // Bug: 应该是 (i == 0) 8 `6 \5 t# h+ w- V
.... 0 G1 }! P' \% E2 ]
} 2 ]" j/ `7 O: d+ s/ k/* 是没有问题的。但在c#中会引发一个编译错误(error CS0029: Cannot implicitly convert * w8 d; ]/ Y/ G! p2 w1 ^$ @2 k' v% Otype '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:*/ , D* T6 ]: d- M4 m/ }string str; ; e7 }, X# {5 N2 Q' M
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if(str = Console.ReadLine()) { 8 ~- f1 @' Z! n' s- ~7 | Console.WriteLine("Your comments are: {0}",str); $ X' [. p( Y) g8 _.... ' F' c" b, v. E$ m0 S/* 而必须:*/ + U' Z" v! {- ~# u6 s9 ?3 z6 g' }using System; 1 u- h/ o& i) o1 H; |* gclass BoolTest , r3 c }1 o9 s$ U{ / \( n! ?/ {( S# `
static void Main() { ' O1 q8 R8 g- Q# N8 q% k6 n) u string str = Console.ReadLine();//也可以:string str; + ], H2 m7 N% T# t- r1 C/ T
if(str == "") // if((str = Console.ReadLine()) == "") 7 O$ G4 z! F1 D6 K# k9 Y6 x" ]
Console.WriteLine("i can't read your comments. Please tell me something! O.K.?"); 6 _4 Y7 l6 M! O) u- o5 ~
else / Y( |! \* ?: |* S7 K) G
Console.WriteLine("Your comments are: {0}",str); 6 I3 I9 H5 ~5 R. p8 N: e t) l } ; n9 S# E: `% [" o9 O9 c) T
} / b9 G! r" @; u/* ! d& x5 D1 A5 ?+ ?8 r2 P% n ]$ d9 x我抄了一张预定义类型的简表供大家参考。 - c* d, V; @5 D. Q7 } + h' a4 h3 l, T! ?Type Description Examples + Y, M* z% M! r) S0 b
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object The ultimate base type of all other types object o = new Stack(); 3 q6 ]: ^+ B8 X& Q9 y" J * d$ |( F5 q) S& s8 C! Cstring String type; a string is a sequence of string s = "Hello"; ' o H- o! @7 Z1 ^" l9 A, A, X. ` Unicode characters ^7 [( o g$ X# Z6 R8 [3 A3 R4 W/ j' P l
sbyte 8-bit signed integral type sbyte val = 12; 3 Q9 }1 F( Q, Y4 C0 ~+ V1 w4 B ! J3 \& v) h/ q k( F9 mshort 16-bit signed integral type short val = 12; ( \5 c8 B3 W' j9 d" R
2 Z% ]5 X5 E2 R) a; {) tint 32-bit signed integral type int val = 12; 5 `2 `! [0 N3 ?9 o4 p) d2 i8 J3 l/ w0 G/ {- J
long 64-bit signed integral type long val1 = 12; 3 X7 P, _ v: w6 Q long val2 = 34L; " J$ o% A) ^& V! T2 ?
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byte 8-bit unsigned integral type byte val1 = 12; . m. {8 O. H8 J! v x2 ]8 P
byte val2 = 34U; " h0 w- f) |: n9 c' T( v
, V1 r$ E5 X' u3 I. C( }1 J% Wushort 16-bit unsigned integral type ushort val1 = 12; 7 c0 n1 D- w0 y# ~- J; g5 t9 Q' T
ushort val2 = 34U; ' [$ {! g% ~3 C: d+ K8 R, u7 |) o+ ]/ v9 t$ O
uint 32-bit unsigned integral type uint val1 = 12; 3 k- J% N4 @5 A {/ X" b
uint val2 = 34U; $ }" a$ D4 ~7 `& { , ~5 V: |0 P4 C2 {$ I1 w! Kulong 64-bit unsigned integral type ulong val1 = 12; ' |% S( s) q2 ~4 | ulong val2 = 34U; , ^( @- e4 s: O; q* b8 X, k ulong val3 = 56L; . Y% E+ ]+ {2 ?) n! D: W! W. P) r& Y+ y ulong val4 = 78UL; ' z# [4 b) \: n8 V
) u, B( M) [* o+ W+ i) ~float Single-precision floating point type float value = 1.23F; # @* G5 b/ m9 j6 i
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double Double-precision floating point type double val1 = 1.23 6 J1 j t( ^* R; K- K$ l# g! F( }8 S double val2 = 4.56D; 1 f+ V" k! g. v 6 W% N1 d4 i2 jbool Boolean type; a bool value is either bool value = true; * d3 O b" x" J! r2 k: \% J7 Z! j true or false 9 D5 H) z* A r ( T/ f: _4 P0 ochar Character type; a char value is a Unicode char value = 'h'; 6 r- O) ?7 G; z( c* i8 R5 q character 4 Z" E: G8 f7 T7 j( B" c6 z4 p
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decimal Precise decimal type with 28 significant digits decimal value = 1.23M; . L# d. q% U- \% [% c# U3 p
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你也可以自定义自己的预定义类型,可以这样:*/ ! C: O+ p9 Y2 b, f. B. w% }1 J# yusing System; ! e8 P/ }0 I. u8 _
struct Digit 6 D$ _& b# h+ T- e+ K; q `
{...} : F* Y5 X: B: V3 _/ n* \/ Y mclass Test + T5 [( ]3 w& ?( v+ ]$ e$ B5 `% ~{ " x; I$ Z/ H, X9 p" d: H8 n static void TestInt() { & `( [) V6 D& `1 n( g
int a = 1; ( q- @3 [' |2 U4 u4 Q4 w* i3 \
int b = 2; 1 \5 N0 b: H- q' e
int c = a + b; 9 j+ b& T6 L& j Console.WriteLine(c); ! ~1 _% ^1 n! R& ]" X8 n } : d" |2 j3 V; m/ x static void TestDigit() { 6 \1 O3 f' w+ S Digit a = (Digit) 1; / e; y# w1 j4 P" T; s
Digit b = (Digit) 2; + H' l! y$ v3 s$ @9 L% n$ j Digit c = a + b; 4 e" M/ f! I5 h, W2 F& P/ @ Console.WriteLine(c); ' u. @0 Y. d/ ]* y' Z5 O } + P7 s+ O% B: X$ m/ W% `
static void Main() { : s1 p) J) U ]! G4 y! O5 @" L& l TestInt(); # {: f# E. T" E: o* R6 y TestDigit(); ! g& B- F8 y- y' L } ! ^, w# v' e) ^# |3 b- D& r3 c9 s
} ( N% d4 _! F) d; D$ ?# H/* ) U; X) }& t; C( O! S: j+ Y+ g" I$ c, y这一节有点沉闷。:( O+ F5 W' ]: e* W# t: v( |& D 0 Q) l& S" J9 A6 C+ i<IMG> <IMG> <IMG> ~( _% L, g* [4 F: ^/ T
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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> Q0 C8 V7 D& _5 w% ?: 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>. O& h& i3 f8 k6 S. U8 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! % q+ N) S4 F+ O& J. v" t8 }4 S兄弟再来,我喜欢看。1 a7 S, \, `* Y$ k