Beginner with c# 4

1¡£4 Ô¤¶¨ÒåÀàÐÍ£¨Predefined types£©

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¶¼ÖªµÀ£º*/
int i = 0;
if (i = 0) { // Bug: Ó¦¸ÃÊÇ (i == 0)
....
}
/* ÊÇûÓÐÎÊÌâµÄ¡£µ«ÔÚc#ÖлáÒý·¢Ò»¸ö±àÒë´íÎó£¨error CS0029: Cannot implicitly convert
type 'int' to 'bool'£©¡£µ±È»£¬ÕâÑùÎþÉüÁËÒ»µãûÓбØÒªµÄÁé»îÐÔ¡£ÎÒÃÇÔÙÒ²²»ÄÜÕâÑù£º*/
string str;
....
if(str = Console.ReadLine()) {
  Console.WriteLine("Your comments are: {0}",str);
....
/* ¶ø±ØÐ룺*/
using System;
class BoolTest
{
  static void Main() {
    string str = Console.ReadLine();//Ò²¿ÉÒÔ£ºstring str;
    if(str == "")                   //        if((str = Console.ReadLine()) == "")
      Console.WriteLine("i can't read your comments. Please tell me something! O.K.?");
    else
      Console.WriteLine("Your comments are: {0}",str);
  }
}
/*
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Type      Description                                      Examples

object    The ultimate base type of all other types        object o = new Stack();

string    String type; a string is a sequence of           string s = "Hello";
          Unicode characters

sbyte     8-bit signed integral type                       sbyte val = 12;

short     16-bit signed integral type                      short val = 12;

int       32-bit signed integral type                      int val = 12;

long      64-bit signed integral type                      long val1 = 12;
                                                           long val2 = 34L;

byte      8-bit unsigned integral type                     byte val1 = 12;
                                                           byte val2 = 34U;

ushort    16-bit unsigned integral type                    ushort val1 = 12;
                                                           ushort val2 = 34U;

uint      32-bit unsigned integral type                    uint val1 = 12;
                                                           uint val2 = 34U;

ulong     64-bit unsigned integral type                    ulong val1 = 12;
                                                           ulong val2 = 34U;
                                                           ulong val3 = 56L;
                                                           ulong val4 = 78UL;

float     Single-precision floating point type             float value = 1.23F;

double    Double-precision floating point type             double val1 = 1.23
                                                           double val2 = 4.56D;

bool     Boolean type; a bool value is either              bool value = true;
         true or false

char     Character type; a char value is a Unicode         char value = 'h';
         character

decimal  Precise decimal type with 28 significant digits   decimal value = 1.23M;

ÄãÒ²¿ÉÒÔ×Ô¶¨Òå×Ô¼ºµÄÔ¤¶¨ÒåÀàÐÍ£¬¿ÉÒÔÕâÑù£º*/
using System;
struct Digit
{...}
class Test
{
 static void TestInt() {
  int a = 1;
  int b = 2;
  int c = a + b;
  Console.WriteLine(c);
 }
 static void TestDigit() {
  Digit a = (Digit) 1;
  Digit b = (Digit) 2;
  Digit c = a + b;
  Console.WriteLine(c);
 }
 static void Main() {
  TestInt();
  TestDigit();
 }
}
/*
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