value 的默认参数必须是编译时常量吗? [英] Default parameter for value must be a compile time constant?

问题描述

这是我的方法签名.在尝试将 end 作为可选参数传递时，它给了我这个错误.我应该怎么做才能解决这个问题?为什么 DateTime.MinValue 不是常量?

This is my method signature. While trying to pass end as an optional parameter it gives me this error. What should I do to resolve this? Why isn't DateTime.MinValue a constant?

public static void DatesToPeriodConverter(DateTime start, DateTime end = DateTime.MinValue,
                                          out string date, out string time)

推荐答案

DateTime.MinValue 不是 const，因为语言不喜欢 const 在 DateTime 上.一种选择是使用 DateTime? 代替，即

DateTime.MinValue is not a const, because the language doesn't like const on DateTime. One option is to use DateTime? instead, i.e.

public static void DatesToPeriodConverter(DateTime start, DateTime? end = null,
     out string date, out string time)
{
    var effectiveEnd = end ?? DateTime.MinValue;
    // ...
}

但是，您仍然会遇到在默认参数之后使用非默认参数的问题 - 您可能需要重新排序它们以将其用作默认值.

However, you will still have the issue of having non-default parameters after default parameters - you may need to re-order them to use that as a default.

这篇关于value 的默认参数必须是编译时常量吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！