左位转移255（作为一个字节） [英] Left bit shifting 255 (as a byte)

问题描述

任何人都可以解释为什么以下不编译？

Can anyone explain why the following doesn't compile?

byte b = 255 << 1

错误：

恒值'510'不能被转换为字节

Constant value '510' cannot be converted to a 'byte'

我期待在二元以下内容：

I'm expecting the following in binary:

1111 1110

该类型转换难倒我了。

The type conversion has stumped me.

推荐答案

在C＃数字文本是 INT ，而不是字节（和位移位将被由编译器进行评价的，因此只有510遗体）。因此，您尝试将值赋给字节不适合。你可以用255面膜：

Numeric literals in C# are int, not byte (and the bit shift will be evaluated by the compiler, hence only the 510 remains). You are therefore trying to assign a value to a byte which does not fit. You can mask with 255:

byte b = (255 << 1) & 0xFF

再次降低结果为8位。与Java，C＃不允许通过溢出未被发现去。基本上，你有两个选择明智试图分配510字节时：要么在最大值钳，那么你会得到255，或者扔掉不适合位，在这种情况下，你会得到254。

to reduce the result to 8 bits again. Unlike Java, C# does not allow overflows to go by undetected. Basically you'd have two sensible options when trying to assign 510 to a byte: Either clamp at the maximum value, then you'd get 255, or throw away the bits that do not fit, in which case you'd get 254.

您也可以使用选中，作为<一个href=\"http://stackoverflow.com/questions/737781/left-bit-shifting-255-as-a-byte/737810#737810\">lassevk上述：

byte b = unchecked((byte)(255 << 1));

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