为什么C＃不要求转换长增加一倍显式转换？ [英] Why C# does not require explicit casting for convert Long To Double?

问题描述

首先，对不起，我的英语不好。
我的代码片段：

At first, sorry for my bad english. I have fragment of code:

long x = 9223372036854775807L;
double f = x;
Console.WriteLine(x);           
Console.WriteLine(f);

输出是：

9223372036854775807
9,22337203685478E+18

我没有变任何错误，在编译和执行这些代码。
我们有精度损失，而长转换为双。
为什么C＃不要求在这种情况下显式转换？

I'm not getting any errors while compiling and execution this code. We have a loss of precision while converting Long to Double. Why C# does not require explicit casting in that case ?

谢谢大家。

推荐答案

语言有内置的一些隐式转换。

The language has some implicit conversion built into it.

下表是从文档，这就是为什么你被允许没有显式类型转换或转换指定值：

The following table is from the documentation, which is why you are allowed to assign the value without an explicit cast or conversion:

From        To
===============================================================================
sbyte       short , int, long, float, double, or decimal
byte        short , ushort, int, uint, long, ulong, float, double, or decimal
short       int , long, float, double, or decimal
ushort      int , uint, long, ulong, float, double, or decimal
int         long , float, double, or decimal
uint        long , ulong, float, double, or decimal
long        float , double, or decimal
char        ushort , int, uint, long, ulong, float, double, or decimal
float       double
ulong       float , double, or decimal

和文档中其国家（重点煤矿）：

And in the documentation it states (emphasis mine):

的精度，但幅度可能在会丢失从
INT，UINT，长或ulong的转换，从长期浮动和或ULONG翻番

Precision but not magnitude might be lost in the conversions from int, uint, long, or ulong to float and from long or ulong to double.

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