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");