int占几个字节？

class Program19
    {
        static void Main(string[] args)
        {
            // true，或false
            Console.WriteLine("bool占用:" + sizeof(bool));
            //0-255
            Console.WriteLine("byte 占用:"+sizeof(byte));
            //-128 到 127
            Console.WriteLine("sbyte 占用:" + sizeof(sbyte));
            Console.WriteLine("char 占用:" + sizeof(char));
            //-79228162514264337593543950335 到 + 79228162514264337593543950335
            Console.WriteLine("decimal 占用:" + sizeof(decimal));
            //±5.0 × 10−324 到 ±1.7 × 10308     15-16 位
            Console.WriteLine("double 占用:" + sizeof(double));
            //±1.5 x 10−45 至 ±3.4 x 1038 7位
            Console.WriteLine("float 占用:" + sizeof(float));
            //-2,147,483,648 到 2,147,483,647     带符号的 32 位整数
            Console.WriteLine("int 占用:" + sizeof(int));
            //0 到 4,294,967,295     无符号的 32 位整数
            Console.WriteLine("uint 占用:" + sizeof(uint));
            //-9,223,372,036,854,775,808 到 9,223,372,036,854,775,807     64 位带符号整数
            Console.WriteLine("long 占用:" + sizeof(long));
            //0 到 18,446,744,073,709,551,615     无符号 64 位整数
            Console.WriteLine("ulong 占用:" + sizeof(ulong));
            //-32,768 到 32,767     有符号 16 位整数
            Console.WriteLine("short 占用:" + sizeof(short));
            //0 到 65,535     无符号 16 位整数
            Console.WriteLine("ushort 占用:" + sizeof(ushort));
            byte[] bytes = Encoding.UTF8.GetBytes("我们");
            Console.WriteLine(Encoding.GetEncoding("gb2312").GetBytes("我们").Length);
            Console.WriteLine(bytes.Length);
            Console.ReadLine();
        }
    }

string占用的字节数和编码有关系，如果是UTF8则每个汉字占用3个字节，如果是gb2312则占用2个字节

 2、而在实际的运行中，到底分配多少字节是和编译器有关系，来看一下c#生成好的EXE文件的IL代码：

 static void Main()
        {
            int a8 = 8;
            int a = 32;
            Int16 a16 = 32767;
            Int32 a32 = 2147483647;
            Int64 a64 = 9223372036854775807;
            Int64 aa64 = 8;
            Int64 aaa64 = 32;
            Console.WriteLine(a);
            Console.WriteLine(a8);
            Console.WriteLine(a16);
            Console.WriteLine(a32);
            Console.WriteLine(a64);
        }

看一下IL代码：

.method private hidebysig static void  Main() cil managed
{
  .entrypoint
  // Code size       75 (0x4b)
  .maxstack  1
  .locals init ([0] int32 a8,
           [1] int32 a,
           [2] int16 a16,
           [3] int32 a32,
           [4] int64 a64,
           [5] int64 aa64,
           [6] int64 aaa64)
  IL_0000:  nop
  IL_0001:  ldc.i4.8
  IL_0002:  stloc.0
  IL_0003:  ldc.i4.s   32
  IL_0005:  stloc.1
  IL_0006:  ldc.i4     0x7fff
  IL_000b:  stloc.2
  IL_000c:  ldc.i4     0x7fffffff
  IL_0011:  stloc.3
  IL_0012:  ldc.i8     0x7fffffffffffffff
  IL_001b:  stloc.s    a64
  IL_001d:  ldc.i4.8
  IL_001e:  conv.i8
  IL_001f:  stloc.s    aa64
  IL_0021:  ldc.i4.s   32
  IL_0023:  conv.i8
  IL_0024:  stloc.s    aaa64
  IL_0026:  ldloc.1
  IL_0027:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_002c:  nop
  IL_002d:  ldloc.0
  IL_002e:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_0033:  nop
  IL_0034:  ldloc.2
  IL_0035:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_003a:  nop
  IL_003b:  ldloc.3
  IL_003c:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_0041:  nop
  IL_0042:  ldloc.s    a64
  IL_0044:  call       void [mscorlib]System.Console::WriteLine(int64)
  IL_0049:  nop
  IL_004a:  ret
} // end of method Program2::Main

可以看到，同样定义的是Int64的类型，1个是8，1个是32，1个是9223372036854775807

前两个都是4个字节：ldc.i4.8   ldc.i4.s 

而后一个就是8个字节：ldc.i8