问题描述

我想在属性参数中放置一个恒定的日期时间，我如何制作一个恒定的日期时间?它与 EntLib 验证应用程序块的 ValidationAttribute 相关，但也适用于其他属性.

I would like to put a constant date time in an attribute parameter, how do i make a constant datetime? It's related to a ValidationAttribute of the EntLib Validation Application Block but applies to other attributes as well.

当我这样做时:

private DateTime _lowerbound = new DateTime(2011, 1, 1);
[DateTimeRangeValidator(_lowerbound)]

我会得到:

An object reference is required for the non-static field, method, or property _lowerbound

通过这样做

private const DateTime _lowerbound = new DateTime(2011, 1, 1);
[DateTimeRangeValidator(_lowerbound)]

我会得到:

类型System.DateTime"不能声明为 const

The type 'System.DateTime' cannot be declared const

有什么想法吗?走这条路并不可取:

Any ideas? Going this way is not preferable:

[DateTimeRangeValidator("01-01-2011")]

推荐答案

我一直读到的解决方案是要么走字符串的路线，要么将日/月/年作为三个单独的参数传递，如C# 目前不支持 DateTime 文字值.

The solution I've always read about is to either go the route of a string, or pass in the day/month/year as three separate parameters, as C# does not currently support a DateTime literal value.

这是一个简单的例子，它可以让您将三个 int 类型的参数或 string 类型的参数传递给属性:

Here is a simple example that will let you pass in either three parameters of type int, or a string into the attribute:

public class SomeDateTimeAttribute : Attribute
{
    private DateTime _date;

    public SomeDateTimeAttribute(int year, int month, int day)
    {
        _date = new DateTime(year, month, day);
    }

    public SomeDateTimeAttribute(string date)
    {
        _date = DateTime.Parse(date);
    }

    public DateTime Date
    {
        get { return _date; }
    }

    public bool IsAfterToday()
    {
        return this.Date > DateTime.Today;
    }
}

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