C#中一些很基础但有经常导致错误的一些概念
char 的双重身份
char表示字符但却被看成是整数家族的一部分,它所表示的值是一个无符号整数,它可以参加计算,并可以隐式转换成int,long,ushort,uint和ulong
我看一下下面的例子就明白了:
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using System;
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public class Characters
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{
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public static void Main()
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{
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char firstSymbol;
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char secondSymbol;
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int intFirstSymbol;
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int intSecondSymbol;
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int result;
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firstSymbol = '\u0034';
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secondSymbol = '\u0039';
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Console.WriteLine("firset as charactor:{0}",firstSymbol);
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Console.WriteLine("SecondSymbol as Charactor:{0}",secondSymbol);
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intFirstSymbol = firstSymbol;
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intSecondSymbol = secondSymbol;
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Console.WriteLine("firstSymbol as int:{0}",intFirstSymbol);
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Console.WriteLine("SecondSymbol as int:{0}",intSecondSymbol);
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result = firstSymbol + secondSymbol;
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Console.WriteLine("result as int:{0}",result);
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Console.WriteLine("result as character:{0}",(char)result);
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}
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}
运行结果:![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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\u0034为字符4的Unicode值,\u0039为字符‘9’的Unicode值。
关于“++ --”操作符 放在操作数的前面和后面的区别
很多人都会认为 “++ --” 操作符放在变量的前后是没有区别的,看下面这段代码:
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using System;
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class PlusPlus
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{
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public static void Main()
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{
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int a=5;
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int b=10;
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Console.WriteLine("a++ = {0}",a++);
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Console.WriteLine("++b = {0}",++b);
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}
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}
运行结果:![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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a++ = 5
++b = 11
在代码中我们把操作符“++”分别放在变量“a”和变量“b”的前面和后面,但是输出的结果却是不同的,放在后面的a变量输出的结果没事使a变量增加,而操作符放在前面的b变量却自动增加了,一般我们都不会注意到这点,以至于我们在程序中出现了这样的错误我们都找不到原因,这是因为操作符“++ --”如果放在变量的后面是在整个表达式完成运算以后才会自增1,而放在放在前面则是先自增以后再参与表达式的运算。