c# - 将整数转换为ASCII然后再返回整数后，为什么会得到一个不同的值？

Question

为什么当我将INT值转换为字节，再转换为ASCII并返回时，又得到另一个值？
例子:

var asciiStr = new string(Encoding.ASCII.GetChars(BitConverter.GetBytes(2000)));
var intVal = BitConverter.ToInt32(Encoding.ASCII.GetBytes(asciiStr), 0);
Console.WriteLine(intVal);

// Result: 1855

Answer 1

ASCII仅是7位-不支持127以上的代码点。每个the docs on ? 会将不支持的字符转换为Encoding.ASCII:

The ASCIIEncoding object that is returned by this property might not have the appropriate behavior for your app. It uses replacement fallback to replace each string that it cannot encode and each byte that it cannot decode with a question mark ("?") character.

因此 2000十进制= D0 07 00 00十六进制(小端)= [unsupported character] [BEL character] [NUL character] [NUL character] = ? [BEL character] [NUL character] [NUL character] = 3F 07 00 00十六进制(小端)= 1855十进制。