c# - null 动态变量和函数重载

Question

示例代码:

private void DoSomething(object obj)
{
    MessageBox.Show("called object");
}

private void DoSomething(params object[] obj)
{
    MessageBox.Show("called object[]");
}


private void button1_Click(object sender, EventArgs e)
{
    decimal? amount = null;
    dynamic obj = amount;

    DoSomething(obj); 
}

单击按钮 1 时，将显示消息“调用的对象[]”。似乎在此示例中首选带有 object[] 参数的重载方法。任何想法为什么？我只是好奇胜过一切。

(背景:此行为在具有动态 View 的 Razor 中导致了一些意外结果 Formatting nullable decimal in RazorEngine ).

Answer 1

那是因为您可以将 object[] 转换为 object 而不是相反。 object[] 更具体，因此在方法解析中更受欢迎。

7.5.3.2 Better function member

(...)

Given an argument list A with a set of argument expressions { E1, E2, ..., EN } and two applicable function members MP and MQ with parameter types { P1, P2, ..., PN } and { Q1, Q2, ..., QN }, MP is defined to be a better function member than MQ if

• for each argument, the implicit conversion from EX to QX is not better than the implicit conversion from EX to PX, and
• for at least one argument, the conversion from EX to PX is better than the conversion from EX to QX.

随后定义了更好的转化目标:

7.5.3.5 Better conversion target

Given two different types T1 and T2, T1 is a better conversion target than T2 if at least one of the following holds:

• An implicit conversion from T1 to T2 exists, and no implicit conversion from T2 to T1 exists

(...)

在您的示例中，T1 是 object[]，T2 是 object。