c# 基础数据类型

持续创作，加速成长！这是我参与「掘金日新计划 · 6 月更文挑战」的第6天，点击查看活动详情 c# 基础数据类型格式及范围

bool -> System.Boolean (布尔型，其值为 true 或者 false)
decimal->System.Decimal(表示十进制数，占16个字节)
byte -> System.Byte (字节型，占 1 字节，表示 8 位正整数，范围 0 ~ 255)
sbyte -> System.SByte (带符号字节型，占 1 字节，表示 8 位整数，范围 -128 ~ 127)
char -> System.Char (字符型，占有两个字节，表示 1 个 Unicode 字符)
short -> System.Int16 (短整型，占 2 字节，表示 16 位整数，范围 -32,768 ~ 32,767)
ushort -> System.UInt16 (无符号短整型，占 2 字节，表示 16 位无符号整数，范围 0 ~ 65,535)
uint -> System.UInt32 (无符号整型，占 4 字节，表示 32 位无符号整数，范围 0 ~ 4,294,967,295)
int -> System.Int32 (整型，占 4 字节，表示 32 位整数，范围 -2,147,483,648 到 2,147,483,647)
float -> System.Single (单精度浮点型，占 4 个字节，范围-3.40282347E+38F到3.40282347E+38F)
ulong -> System.UInt64 (无符号长整型，占 8 字节， 表示 64 位无符号整数，范围 0 ~ 大约 10 的 20 次方)
long -> System.Int64 (长整型，占 8 字节， 表示 64 位有符号整数，范围大约 -(10 的 19) 次方 到 10 的 19 次方)
double -> System.Double (双精度浮点型，占8 个字节，范围（-1.7976931348623157E+308，1.7976931348623157E+308）)

• c# Duff优化for循环耗时

看Js高级编程的时候 发现了一个叫duff 可以优化for循环的

感觉比较有趣简单 写了一个c#版的

winfrom的三个button的代码如下 如果要效果明显 可以增大for 循环长量的值

        public const int Counts= 10000000;
        private void button1_Click(object sender, EventArgs e)
        {
            double A = 0;
            List<int> Old = new List<int>();
            for (int j= 0; j < Counts; j++)
            {
                Old.Add(j);
            }
            Stopwatch sw = new Stopwatch();
            sw.Start();

            //  
            int iterations =(int)Math.Ceiling((Old.Count*1.0 / 8));
            int startAt = Old.Count % 8;
            var i = 0;
            do
            {
                switch (startAt)
                {
                    case 0:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 7:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 6:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 5:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 4:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 3:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 2:
                        A += (Old[i++]);
                        A += (Old[i++]);
                        break;
                    case 1:
                        A += (Old[i++]);
                        break;
                }
                startAt = 0;
            } while (--iterations > 0);

            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine(A.ToString());
            Console.WriteLine("Stopwatch总共花费{0}ms.", ts2.TotalMilliseconds);

        }

        private void button2_Click(object sender, EventArgs e)
        {
            double A2 = 0;
            List<int> Old2 = new List<int>();
            for (int j = 0; j < Counts; j++)
            {
                Old2.Add(j);
            }
            Stopwatch sw = new Stopwatch();
            sw.Start();

            for (int i = 0; i < Old2.Count; i++)
            {
                A2 += Old2[i];
            }

            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine(A2.ToString());
            Console.WriteLine("Stopwatch总共花费{0}ms.", ts2.TotalMilliseconds);
        }

        private void button3_Click(object sender, EventArgs e)
        {
            double A3 = 0;
            List<int> Old3 = new List<int>();
            for (int j = 0; j < Counts; j++)
            {
                Old3.Add(j);
            }
            Stopwatch sw = new Stopwatch();
            sw.Start();
            int a = Old3.Count;
            for (int i = 0; i < a; i++)
            {
                A3 += Old3[i];
            }

            sw.Stop();
            TimeSpan ts2 = sw.Elapsed;
            Console.WriteLine(A3.ToString());
            Console.WriteLine("Stopwatch总共花费{0}ms.", ts2.TotalMilliseconds);
        }