关于C#数据类型之间转换的问题!

 

关于C#数据类型之间转换的讨论

在装箱，拆箱过程中，首先涉及到的是数据的转换。发下午几个小时，研究了C#中数据类型之间的转换涉及的一些问题，希望大家给予意见！

1、数据类型的类名

这里讲的数据的类名指的是： Sytem.data.DbType对应的类型，我是这样理解的。

类名      System中相对应的类型

bool     System.Boolean (布尔型，其值为 true 或者 false)
char     System.Char (字符型，占有两个字节，表示 1 个 Unicode 字符)
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)
ushort   System.UInt16 (无符号短整型，占 2 字节，表示 16 位正整数，范围 0 ~ 65,535)
uint     System.UInt32 (无符号整型，占 4 字节，表示 32 位正整数，范围 0 ~ 4,294,967,295)
ulong    System.UInt64 (无符号长整型，占 8 字节，表示 64 位正整数，范围 0 ~ 大约 10 的 20 次方)
short    System.Int16 (短整型，占 2 字节，表示 16 位整数，范围 -32,768 ~ 32,767)
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)
long     System.Int64 (长整型，占 8 字节，表示 64 位整数，范围大约 -(10 的 19) 次方到 10 的 19 次方)
float     System.Single (单精度浮点型，占 4 个字节)
double  System.Double (双精度浮点型，占 8 个字节)

代码如下：

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace TypeTest

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            bool bo = true;

            byte b = 9;

            char c = 'a';

            sbyte sb = 8;

            short s = 8;

            int i= 7;

            uint u = 6;

            long l = 5;

            this.textBox1.Text = "typetest";

            this.textBox1.AppendText("bool -> " + bo.GetType().FullName + ""n");

            this.textBox1.AppendText("byte -> " + b.GetType().FullName + ""n");

            this.textBox1.AppendText("char -> " + c.GetType().FullName + ""n");

            this.textBox1.AppendText("sbyte -> " + sb.GetType().FullName + ""n");

            this.textBox1.AppendText("short -> " +s.GetType().FullName + ""n");

            this.textBox1.AppendText("int -> " + i.GetType().FullName + ""n");

            this.textBox1.AppendText("uint -> " +u.GetType().FullName + ""n");

            this.textBox1.AppendText("long -> " +l.GetType().FullName + ""n");

            //其实类型就不写上，自己可以真接加上去！

        }

    }

}

结果可看到：

typetestbool -> System.Boolean

byte -> System.Byte

char -> System.Char

sbyte -> System.SByte

short -> System.Int16

int -> System.Int32

uint -> System.UInt32

long -> System.Int64

//

说明，以后所编的代码都是写在private void Form1_Load(object sender, EventArgs e)中的

2、Value Type间的转换。

bool bo = true;

            byte b = 9;

            char c = 'a';

            sbyte sb = 8;

            short s = 8;

            int i = 7;

            uint u = 6;

            long l = 5;

            this.textBox1.Text = "datatype";

            this.textBox1.AppendText("bool bo=" + bo.ToString() + ""n");

            this.textBox1.AppendText("byte b= " + b.ToString() + ""n");

            this.textBox1.AppendText("char c= " + c.ToString() + ""n");

            this.textBox1.AppendText("sbyte sb= " + sb.ToString() + ""n");

            this.textBox1.AppendText("short s= " + s.ToString() + ""n");

            this.textBox1.AppendText("int i= " + i.ToString() + ""n");

            this.textBox1.AppendText("uint u=" + u.ToString() + ""n");

        this.textBox1.AppendText("long l= " + l.ToString() + ""n");

此段代码并没有转换数据类型，只说明它们的类型公别还是System.bool型…System.long型。

追加一行：int g = 1;
short h = g;
this.textBox1.AppendText("h = " + h.ToString() + ""n");

结果编译报错：
　　G:"Projects"Visual C#"Convert"Form1.cs(118): 无法将类型“int”隐式转换为“short”
数据要进行强制转换。

如上例修改如下：

short g = 1;
byte h = (byte) g; // 将 short 型的 g 的值强制转换成byte型后再赋给变量 h
this.textBox1.AppendText("h = " + h.ToString() + ""n");

就可以了！

Short->byte

       short g = 265; //265 = 255 + 10
byte h = (byte) g;
this.textBox1.AppendText("h = " + h.ToString() + ""n");

注意：溢出问题！

3、ASCII<->Unicode
char ch = 'a';

            short ii = 65;

            this.textBox1.Text = "";

            this.textBox1.AppendText("The ASCII code of "'" + ch + ""' is: " + (short)ch + ""n");

            this.textBox1.AppendText("ASCII is " + ii.ToString() + ", the char is: " + (char)ii + ""n");

            char name1 = '屈';

            char name2 = '志';

            short name3 = 21195;

            this.textBox1.AppendText("The Unicode of "'" + name1 + ""' is: " + (short)name1 + ""n");

            this.textBox1.AppendText("The Unicode of "'" + name2 + ""' is: " + (short)name2+ ""n");

            this.textBox1.AppendText("Unicode is " + name3.ToString() + ", the name3 is: " + (char)name3 + ""n");
　　它的运行结果是

The ASCII code of 'a' is: 97

ASCII is 65, the char is: A

The Unicode of '屈' is: 23624

The Unicode of '志' is: 24535

Unicode is 21195, the name3 is: 勋

4、int<->string

float f = 12.3f;

            string str = "258";

            this.textBox1.Text = "";

            this.textBox1.AppendText("f = " + f.ToString() + ""n");//float->string

            if (int.Parse(str) == 258) //string->int

            {

                this.textBox1.AppendText("str convert to int successfully.");

            }

            else

            {

                this.textBox1.AppendText("str convert to int failed.");

5、String<->char[]

string str = "quzhixun";

            char[] chars = str.ToCharArray();//string->char[]

            this.textBox1.Text = "";

            this.textBox1.AppendText("Length of ""quzhixun"" is " + str.Length + ""n");

            this.textBox1.AppendText("Length of char array is " + chars.Length + ""n");

            this.textBox1.AppendText("char[2] = " + chars[2] + ""n");

char[] name = { 'q', 'u', 'z', 'h', 'i', 'x', 'u','n' };

            string sname = new String(name);//char[]->string

            this.textBox1.AppendText("sname = """ + sname + """"n");

6、tring<->byte[]

string s = "hi,屈志勋";

            byte[] b1 = System.Text.Encoding.Default.GetBytes(s);//sting->byte[],半个英文1个字节，汉字2 个字节。

            byte[] b2 = System.Text.Encoding.Unicode.GetBytes(s); //sting->byte[],都是两个字节。

            string t1 = "", t2 = "";

            foreach (byte b in b1)

            {

                t1 += b.ToString("") + " ";

            }

            foreach (byte b in b2)

            {

                t2 += b.ToString("") + " ";

            }

            this.textBox1.Text = "";

            this.textBox1.AppendText("b1.Length = " + b1.Length + ""n");

            this.textBox1.AppendText(t1 + ""n");

            this.textBox1.AppendText("b2.Length = " + b2.Length + ""n");

        this.textBox1.AppendText(t2 + ""n");

//

byte[] b = { 65, 66, 67 };

            string s = System.Text.Encoding.ASCII.GetString(b);//byte[]->string

            this.textBox1.AppendText("The string is: " + s + ""n");

//

7、转换十六进制

int a = 159357;

            this.textBox1.Text = "";

            this.textBox1.AppendText("a(10) = " + a.ToString() + ""n");

            this.textBox1.AppendText("a(16) = " + a.ToString("x6") + ""n");

       this.textBox1.AppendText("a(16) = " + a.ToString("X6") + ""n");

8、DateTime<->long

double doubleDate = DateTime.Now.ToOADate();//按原来的double值输出，DateTime->long

            DateTime theDate = DateTime.FromOADate(doubleDate);//从原来的的double值获得System.DateTime对象,long->DateTime

            this.textBox1.Text = "";

            this.textBox1.AppendText("Double value of now: " + doubleDate.ToString() + ""n");

       this.textBox1.AppendText("DateTime from double value: " + theDate.ToString() + ""n");

//

9、form DateTime

DateTime now = DateTime.Now;

            string format;

            this.textBox1.Text = "";

            format = """year"":yyyy,""month"":MM,""day"":dd HH:mm:ss";

            this.textBox1.AppendText(format + ": " + now.ToString(format) + ""n");

            format = "yy年M日d日";

       this.textBox1.AppendText(format + ": " + now.ToString(format) + ""n");