c# - 使用条件运算符时控制台将 char 显示为 int ( ? : )

Question

我对下面代码的输出感到惊讶

public static void Main(string[] args)
{
    char x = 'A';
    int i = 0;
    Console.WriteLine (true  ? x : 0);
    Console.WriteLine(false ? i : x); 
}

当我在阅读 C# 面试问题时，我看到了这段代码，上面代码的输出是

输出

65
65

我想知道这是怎么发生的。

有人可以解释一下吗？谢谢!

Answer 1

'A' 是一个 char 并且值为 65

然而，对于为什么这会导致一个整数(而不是 char 的字符串表示)有一个技术解释，您可以在 ECMA C# specifications 中找到它。

12.15 条件运算符

The second and third operands, x and y, of the ?: operator control the type of the conditional expression.

• If x has type X and y has type Y then,
  • If X and Y are the same type, then this is the type of the conditional expression.
  • Otherwise, if an implicit conversion (§11.2) exists from X to Y, but not from Y to X, then Y is the type of the conditional expression.
  • Otherwise, if an implicit enumeration conversion (§11.2.4) exists from X to Y, then Y is the type of the conditional expression.
  • Otherwise, if an implicit enumeration conversion (§11.2.4) exists from Y to X, then X is the type of the conditional expression.
  • Otherwise, if an implicit conversion (§11.2) exists from Y to X, but not from X to Y, then X is the type of the conditional expression.
  • Otherwise, no expression type can be determined, and a compile-time error occurs.
• If only one of x and y has a type, and both x and y are implicitly convertible to that type, then that is the type of the conditional expression.
• Otherwise, no expression type can be determined, and a compile-time error occurs

示例

char Y = 'A';
int X = Y;
Y = X; // compiler error

简而言之，没有从int到char的隐式转换，但是从char到int，所以结果类型是 int

是有意义的