如何在 C# 中返回命名元组? [英] How to return named tuples in C#?

问题描述

我有一个属性返回两个 DateTime 类型的项目.返回这些值时，我必须将它们引用为 Item1 和 Item2.我如何使用自定义名称返回，例如

I have a property that returns two items of type DateTime. When returning these values I have to reference them as Item1 and Item2. How do I return with custom names e.g.

filter?.DateRanges.From
filter?.DateRanges.To

 

public Tuple<DateTime, DateTime> DateRanges
{
    get
    {
        From = DateTime.Now.AddDays(-1).Date.AddMonths(-1);
        To = DateTime.Now.AddDays(-1).Date;

        if (Preset != 0)
        {
            if (Preset == DatePreset.SpecificRange)
            {
                From = From.Date;
                To = To.Date;
            }
            else
            {
                var dateRange = DateTime.Today.AddDays(-1).GetDateRangeByPreset(Preset);
                From = dateRange.From;
                To = dateRange.To;
            }
        }

        return new Tuple<DateTime, DateTime>(From, To);
    }

用法:

var from = filter?.DateRanges.Item1;
var to = filter?.DateRanges.Item2;

推荐答案

像这样:

public (DateTime Start, DateTime End) DateRanges
{
    get
    {
        return (DateTime.MinValue, DateTime.MaxValue);
    }
}

注意:这需要最新版本的 C# 和 .Net.

Note: This requires a recent version of C# and .Net.

顺便提一下，注意这种使用模式:

Incidentally, watch out for this usage pattern:

var from = filter?.DateRanges.Start;
var to = filter?.DateRanges.End;

这是低效的，因为它会导致创建两个相同的元组.

That's inefficient because it causes two identical tuples to be created.

这样更好:

var range = filter?.DateRanges;

if (range.HasValue)
{
    var from  = range.Value.Start;
    var to    = range.Value.End;
}

但是请注意元组不能为空(它们是值类型)所以你可以这样写:

However note that tuples cannot be null (they are value types) so you could write it like so:

if (filter != null)
{
    var range = filter.DateRanges;
    var from  = range.Start;
    var to    = range.End;
    ...
}

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