类和结构的区别

类是引用类型，结构是值类型，下面的例子中 大量使用结构类型

namespace CSharpTest
{
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct LOGFONTW
    {
        public int lfHeight;
        public int lfWidth;
        public int lfEscapement;
        public int lfOrientation;
        public int lfWeight;
        public byte lfItalic;
        public byte lfUnderline;
        public byte lfStrikeOut;
        public byte lfCharSet;
        public byte lfOutPrecision;
        public byte lfClipPrecision;
        public byte lfQuality;
        public byte lfPitchAndFamily;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
        public string lfFaceName;
    }
    public struct SYSTEMTIME
    {
        public ushort wYear;
        public ushort wMonth;
        public ushort wDayOfWeek;
        public ushort wDay;
        public ushort wHour;
        public ushort wMinute;
        public ushort wSecond;
        public ushort wMilliseconds;
    }
    /// <summary>
    /// Point
    /// </summary>
    public struct NP_POINT
    {
        /// <summary>
        /// //水平起始位置
        /// </summary>
        public int X;
        /// <summary>
        /// 垂直起始位置
        /// </summary>
        public int Y;
    }
    //Size
    public struct NP_SIZE
    {
        //宽度
        public int Width;
        //高度
        public int Height;
    };
    //Rectangle
    public struct NP_RECTANGLE
    {
        //x
        public int X;
        //y
        public int Y;
        //宽度
        public int Width;
        //高度
        public int Height;
    };
}

下述代码中两个都使用

 public struct TTimeStamp
    {
        public Int32 time;
        public Int32 date;
    }
    public struct TRoad
    {
        public uint name;
        public uint speed;
    }

    class CLEDSender
    {
        //通讯设备类型
        public readonly ushort DEVICE_TYPE_COM = 0;  //串口通讯
        public readonly ushort DEVICE_TYPE_UDP = 1;  //网络通讯
        public readonly ushort DEVICE_TYPE_485 = 2;  //485通讯

        //串口或者485通讯使用得通讯速度(波特率)
        public readonly ushort SBR_57600 = 0;
        public readonly ushort SBR_38400 = 1;
        public readonly ushort SBR_19200 = 2;
        public readonly ushort SBR_9600  = 3;
        //道路选择
        public readonly ushort ROAD_1 = 0;
         public readonly ushort ROAD_2 = 1;
        public readonly ushort ROAD_3 = 2;
        //速度选择
        public readonly ushort GREEN = 0;
        public readonly ushort RED = 1;
        public readonly ushort YELLOW = 2;

        //是否等待下位机应答，直接发送所有数据
        public readonly UInt32 NOTIFY_NONE  = 1;
        //是否阻塞方式；是则等到发送完成或者超时，才返回；否则立即返回
        public readonly UInt32 NOTIFY_BLOCK = 2;
        //是否将发送结果以Windows窗体消息方式送到调用得应用
        public readonly UInt32 NOTIFY_EVENT = 4;

        public readonly Int32 R_DEVICE_READY    = 0;
        public readonly Int32 R_DEVICE_INVALID  = -1;
        public readonly Int32 R_DEVICE_BUSY     = -2;
        public readonly Int32 R_FONTSET_INVALID = -3;
        public readonly Int32 R_DLL_INIT_IVALID = -4;
        public readonly Int32 R_IGNORE_RESPOND  = -5;

        //下位机应答标识
        public readonly ushort LM_RX_COMPLETE = 1;
        public readonly ushort LM_TX_COMPLETE = 2;
        public readonly ushort LM_RESPOND     = 3;
        public readonly ushort LM_TIMEOUT     = 4;
        public readonly ushort LM_NOTIFY      = 5;
        public readonly ushort LM_PARAM       = 6;
        public readonly ushort LM_TX_PROGRESS = 7;
        public readonly ushort LM_RX_PROGRESS = 8;
        public readonly ushort RESULT_FLASH = 0xff;

下面看下两者的区别

namespace Ch09Ex03
{
class MyClass
{
public int val;
}
struct myStruct
{
public int val;
}
class Program
{
static void Main(string[] args)
{
MyClass objectA = new MyClass();
MyClass objectB = objectA;
objectA.val = 10;
objectB.val = 20;
myStruct structA = new myStruct();
myStruct structB = structA;
structA.val = 30;
structB.val = 40;
Console.WriteLine("objectA.val = {0}", objectA.val);
Console.WriteLine("objectB.val = {0}", objectB.val);
Console.WriteLine("structA.val = {0}", structA.val);
Console.WriteLine("structB.val = {0}", structB.val);
Console.ReadKey();
}
}
}

运行类是引用类型也就是带有指针的，我们所引用的是指针，也就是地址，MyClass objectB = objectA;也即是两个引用类型共用了一个指针（地址相同），你可以这么试下

  static void Main(string[] args)
        {
            MyClass objectA = new MyClass();
            MyClass objectB = objectA;
            objectA.val = 10;
            //objectB.val = 20;
            myStruct structA = new myStruct();
            myStruct structB = structA;
            structA.val = 30;
            structB.val = 40;
            Console.WriteLine("objectA.val = {0}", objectA.val);
            Console.WriteLine("objectB.val = {0}", objectB.val);
            Console.WriteLine("structA.val = {0}", structA.val);
            Console.WriteLine("structB.val = {0}", structB.val);
            Console.ReadKey();
        }
    }

给任意一个值赋值，两个就有相同的值，明白否？