4 T- [* C6 H6 K9 i1 \2 pc#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。 $ j/ m+ {+ a3 C* {+ o
object类型是所有其他类型的基础。 ) u4 D* P o9 y: f5 w! C3 ?8 G8 X# J- @; g5 [# V% d
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、 ; U1 s8 `% C' Z1 U: {1 _8 e& m
int和long；无符号数有：byte、ushort、uint和ulong；浮点数有：float和double。 & H7 i$ P* w. g
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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。 0 q5 g; x h0 |( \3 e
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 $ R! \& G* G3 {% d4 s9 X: ~都知道：*/ + ?5 t- ?" @; m( X- |1 T/ i. j
int i = 0; - q. A6 W5 ~! P7 f" X& `if (i = 0) { // Bug: 应该是 (i == 0) ' B/ X# W9 B+ I3 E. @/ {2 c
.... 4 @! e9 N/ o) C1 i} - o3 Y$ z% W0 ?. {6 `/* 是没有问题的。但在c#中会引发一个编译错误（error CS0029: Cannot implicitly convert $ f6 q6 ^7 e1 _# D: b
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：*/ $ X# W5 n- L5 `# B1 U- ? [& ]
string str; 5 B7 Z/ X# G' B; _) P8 m4 Z1 S.... ; O8 i) Y# h+ D' }6 s3 g1 k, Lif(str = Console.ReadLine()) { 5 d8 G) W0 b2 k* `
Console.WriteLine("Your comments are: {0}",str); 0 o3 _# r/ Q5 M6 X1 o3 F
.... % @. F. Z# F: ~( A/* 而必须：*/ 6 e( u8 @% A; p2 S2 s0 gusing System; * g8 u, r+ K' F) M8 C/ S. m6 N2 }
class BoolTest 6 _4 g" M% X; X" N' h8 a, y{ 9 F0 y6 `: s S4 S
static void Main() { 6 V/ f5 x1 O) P string str = Console.ReadLine();//也可以：string str; . Q0 d) r( y+ [! h; B
if(str == "") // if((str = Console.ReadLine()) == "") # P# s7 W1 A3 t, S0 B r l Console.WriteLine("i can't read your comments. Please tell me something! O.K.?"); 3 @+ E+ [* S7 m5 v+ C; b; h else ) N1 K' U2 B! |& l K
Console.WriteLine("Your comments are: {0}",str); . Q2 T* h6 w9 ?/ H
} 4 K2 w" y4 E5 h0 P" W
} ; m; z' X* Y+ C' n; Z3 ]/* 2 X$ b4 }" H0 U- w6 a( z) s* x
我抄了一张预定义类型的简表供大家参考。 , i* t6 w) t: t8 Z, ~$ \; n( ~0 D5 S0 V$ G$ H
Type Description Examples + p5 t4 S5 ?4 r& J- O 0 H I: G5 W, yobject The ultimate base type of all other types object o = new Stack(); 5 W4 N, f5 A) k8 ?- k% T $ i0 I4 q9 V! Q6 Q1 kstring String type; a string is a sequence of string s = "Hello"; * |3 l ~7 G- G3 O2 t
Unicode characters ) X7 F- w6 Y% f- q6 p; G" X 8 B* h& r( k7 a9 _' o1 J0 |sbyte 8-bit signed integral type sbyte val = 12; , d6 B5 A* u! l1 l! G
4 {- [+ E/ I. u1 y( e# X* Y( u2 Gshort 16-bit signed integral type short val = 12; ' {, z& ~' G0 `; r* @: q. u & L- r; \. u6 h: zint 32-bit signed integral type int val = 12; 3 j @$ W. H- ?3 m* ]; I3 O) u, L7 y
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long 64-bit signed integral type long val1 = 12; ; F; R& E6 F9 @, Q# |! ?7 d
long val2 = 34L; 9 m* O% W2 p" t6 i" a* N
, c) S& o2 x; q) K. X& O% F+ b( Cbyte 8-bit unsigned integral type byte val1 = 12; : X7 h7 f. u9 s) Y byte val2 = 34U; - @8 s5 ~, j" E4 R8 {& o. m* u, D6 O P, G
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ushort 16-bit unsigned integral type ushort val1 = 12; $ \+ o* u* j* a$ C% b2 g9 B; Y ushort val2 = 34U; & @$ `8 @+ L2 E0 d* b8 F# L
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uint 32-bit unsigned integral type uint val1 = 12; + z8 T- k8 ~0 Q7 n
uint val2 = 34U; 2 M2 T* b6 o$ B2 \; @. p3 b7 b! a8 _1 H* [- i
ulong 64-bit unsigned integral type ulong val1 = 12; 7 ?: i" ?5 E" m1 n$ e+ z2 l ulong val2 = 34U; ; L( R4 Y N7 f T: }
ulong val3 = 56L; 7 p' y8 u7 h7 O( o; U ulong val4 = 78UL; 6 ~- C8 E: p' o2 g8 r 4 K" e& i5 S1 h6 b! p# zfloat Single-precision floating point type float value = 1.23F; ! D9 H( ]7 I7 m1 Z4 u / _; X/ s) }2 qdouble Double-precision floating point type double val1 = 1.23 1 `& @5 V, ^3 R4 V double val2 = 4.56D; & B) I4 q" e8 C5 b4 y! v5 ~
- l( n m- |3 `2 | ^2 n8 [bool Boolean type; a bool value is either bool value = true; 7 O g2 A/ ~/ G; r4 e! o: M9 L' L) J
true or false * s, x$ x5 Y( D3 L- R- ^ 1 u$ b( V+ [; o" t- Fchar Character type; a char value is a Unicode char value = 'h'; ! R5 e, W8 h& l0 e character 9 @# j1 d' m' b$ ~/ o/ a
- U/ J4 v+ b1 n- Hdecimal Precise decimal type with 28 significant digits decimal value = 1.23M; + P4 E, ^* m* ^( K: n
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你也可以自定义自己的预定义类型，可以这样：*/ + Y- R5 M- Z6 }8 Y8 ~using System; , w" U2 T9 Q3 _
struct Digit ( h- w/ B9 H; w2 O
{...} & y# R; v* p3 a1 w, aclass Test % a# \. m% g/ v6 w8 c. L+ H{ 9 f/ X* B7 q" J. W: m* {5 t static void TestInt() { 5 Y+ }, J0 ^* V& T3 H, ^/ n9 s+ B' Q
int a = 1; : T: {4 _8 F, M/ W9 B1 m8 r
int b = 2; : `" c0 w" B- T5 C |8 u int c = a + b; 1 m0 I* E4 s2 V) S Console.WriteLine(c); 3 K8 @1 m0 Y, q9 H
} 9 P: r) \, @( H6 w( w" I static void TestDigit() { ' i' s* `9 _3 [# X4 V/ W Digit a = (Digit) 1; 6 Q5 L$ g9 e' u; r Digit b = (Digit) 2; ' g0 O$ v: f6 M% E( o; m8 q
Digit c = a + b; ; z; ]8 b: X2 B5 W0 Z+ i y Console.WriteLine(c); * y! l& i7 r# o% x. k7 d( ]/ T
} . n4 w. i2 c8 U- l static void Main() { % N* f/ `1 V- F* y2 | TestInt(); ) i+ y1 B8 W5 q8 b6 `& s# K4 O* \
TestDigit(); 8 n+ E9 l/ Z1 K. N3 D& P } + @+ B* n0 h3 p
} 3 e" r/ E6 R# j' Y, k. T
/* 0 i; e, M, c4 @) E, ]7 f$ {1 M% u这一节有点沉闷。：（8 w' b" d. r2 M