前两天刚看书看到的,来这里跟大家分享一下有关C#处理指令的问题
前两天刚看书看到的,来这里跟大家分享一下,
这些东东就是C# 预处理器的指令了,在我们编译的时候会很有用处.
在处理之前要先定义的一个符号,可以在后面根据条件进行编译,
#define 这便是定义指令.必须在文件的开始处定义才行,不然是产生编译错误
如下定义
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在定义以后我们就要来进行条件设置了,不然就达不到效果,呵呵,
注意: #define 定义的符号在后面的条件计算是为 true
如:
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这样的结果是:Hello World first!在这里我们用到了#else这个跟条件语句里的else上一样的.
因为在开始的时候我们定义了first这个符号.从上面可以看出first是作为布尔变量来计算的.
现在我们将这段代码变换一下
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这里看到的效果是:Hello World Yes all!
上面用到了#elif这相当于条件语句里的 else if
接下来我们看看#undef
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现在看到的结果是:Hello World No all!
为什么,呵呵.是因为我们写了#undef取消了对Debug的定义,也就是说Debug已经不起作用了,
接下来该#warning上场了,故名思义,就是在编译的时候产生警告信息.
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可以看到有Hello Word!
在下面的信息框里可以看到警告信息,编译是已经通过了,
下面继续看其它的指令:#error这是一个产生错误信息的指令如下
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这里就看不到输入的字符了,不过可以在消息框里看到下面的信息
现在来看看#line指令
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这样可以看到消息框有台下信息
#line的功能就显而易见了,他就是将默认的行号改成自己定义的行号.#line后面跟default则是将现在的行号恢复至原来的行号
但是它还有一个功能就是可以隐藏某行代码,这是SDK里对它的解释
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下面的示例说明调试器如何忽略代码中的隐藏行。运行此示例时,它将显示三行文本。但是,当设置如示例所示的断点并按 F10 键逐句通过代码时,您将看到调试器忽略了隐藏行。另请注意,即使在隐藏行上设置断点,调试器仍会忽略它。]
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这段代码在运行后虽然可以看到有三行输入,但是在调试的时候可以发现第二行根本就没有被调试到.
还有最后两个指令了,
#region
#endregion
这两个我想大家都非常熟悉了吧