程序实现:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace _43_数据类型
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("int:" + sizeof(int));        //4字节宽度
            Console.WriteLine("int:" + sizeof(long));       //8字节宽度
            Console.WriteLine("int:" + sizeof(float));      //4字节宽度
            Console.WriteLine("int:" + sizeof(double));     //8字节宽度
            Console.WriteLine("int:" + sizeof(decimal));    //16字节宽度
            ////////////////////////////////////////
            Console.WriteLine("int:" + typeof(int));        //System.Int32
            Console.WriteLine("long:" + typeof(long));      //System.Int64
            Console.WriteLine("float:" + typeof(float));    //System.Single
            Console.WriteLine("double:" + typeof(double));  //System.Double
            Console.WriteLine("decimal:" + typeof(decimal));//System.Decimal
            ///////////////////////////////////////
            //判断某个变量的类型
            int n = 10; double f = 3.14;string s= "goood!";
            Cat kitty = new Cat();
            Console.WriteLine("n:"+n.GetType());            //n:System.Int32
            Console.WriteLine("f:"+f.GetType());            //f:System.Double
            Console.WriteLine("s:" + s.GetType());          //s:System.String
            Console.WriteLine("kitty:" + kitty.GetType());  //kitty:_数据类型_Cat
            Console.WriteLine();                            
        
            /////////////////////////////////////////////
            //获取kitty的类型,
            if (kitty.GetType() == typeof(Cat))
                Console.WriteLine("kitty is a Cat");
            else
                Console.WriteLine("kitty is not a cat");    //kitty is a cat;
        }
    }
    class Cat { }
}