在.Net Framework中,我们常用的时间类型是DateTime。直到.Net6微软加入了两个新的时间类型:DateOnly和TimeOnly,才弥补了之前的不足。
DateOnly:表示仅日期。比如:某人的生日,我只关心日期,就适合用DateOnly。
TimeOnly:表示仅时间。比如:每天定时执行某个任务,我只关心时间,就适合用TimeOnly。
由此可见,DateOnly和TimeOnly都有相应的应用场景。可小编在实际项目中遇到了这样的业务场景:需要每月给客户生成月账单。这里我所关心的是某个月份,于是我首先想到用DateOnly表示(不考虑字符串)。
var date = new DateOnly(2023, 2, 1); // 代表2023年2月1日
虽然DateOnly可用,但从字面理解和表现形式上还是略显尴尬。 DateOnly真正表达的是某一天并不是某个月, 在代码层面也容易混淆,所以并不符合小编的心理期望。经过一番纠结和思考,小编决定自己动手创建一个表示年/月的时间类型:YearMonth。
var ym = new YearMonth(2023, 2); // 代表2023年2月
YearMonth的源码如下:
1 /// <summary>
2 /// 表示年/月的时间类型
3 /// </summary>
4 [JsonConverter(typeof(YearMonthJsonConverter))]
5 public readonly struct YearMonth
6 {
7 public int Year { get; }
8
9 public int Month { get; }
10
11 public YearMonth(int year, int month)
12 {
13 Year = year;
14 Month = month;
15 }
16
17 public YearMonth AddMonths(int value)
18 {
19 var date = new DateOnly(Year, Month, 1);
20 return FromDateOnly(date.AddMonths(value));
21 }
22
24 public YearMonth AddYears(int value)
25 {
26 var date = new DateOnly(Year, Month, 1);
27 return FromDateOnly(date.AddYears(value));
28 }
29
30 public DateOnly FirstDay()
31 {
32 return new DateOnly(Year, Month, 1);
33 }
34
35 public DateOnly LastDay()
36 {
37 var nextMonth = AddMonths(1);
38 var date = new DateOnly(nextMonth.Year, nextMonth.Month, 1);
39 return date.AddDays(-1);
40 }
41
42 public int DaysInMonth()
43 {
44 return DateTime.DaysInMonth(Year, Month);
45 }
46
47 public static YearMonth Current
48 {
49 get { return FromDateTime(DateTime.Now); }
50 }
51
52 public static YearMonth UtcCurrent
53 {
54 get { return FromDateTime(DateTime.UtcNow); }
55 }
56
57 public static YearMonth FromDateOnly(DateOnly dateOnly)
58 {
59 return new YearMonth(dateOnly.Year, dateOnly.Month);
60 }
61
62 public static YearMonth FromDateTime(DateTime dateTime)
63 {
64 return new YearMonth(dateTime.Year, dateTime.Month);
65 }
66
67 public static YearMonth FromString(string s)
68 {
69 if (DateTime.TryParse(s, out var date))
70 {
71 return FromDateTime(date);
72 }
73 throw new ArgumentException("format is error", nameof(s));
74 }
75
76 public override string ToString()
77 {
78 return $"{Year.ToString().PadLeft(4, '0')}-{Month.ToString().PadLeft(2, '0')}";
79 }
80
81 public static bool operator ==(YearMonth left, YearMonth right)
82 {
83 return left.Year == right.Year && left.Month == right.Month;
84 }
85
86 public static bool operator !=(YearMonth left, YearMonth right)
87 {
88 return !(left.Year == right.Year && left.Month == right.Month);
89 }
90
91 public static bool operator >=(YearMonth left, YearMonth right)
92 {
93 return (left.Year > right.Year) || (left.Year == right.Year && left.Month >= right.Month);
94 }
95
96 public static bool operator <=(YearMonth left, YearMonth right)
97 {
98 return (left.Year < right.Year) || (left.Year == right.Year && left.Month <= right.Month);
99 }
100
101 public static bool operator >(YearMonth left, YearMonth right)
102 {
103 return (left.Year > right.Year) || (left.Year == right.Year && left.Month > right.Month);
104 }
105
106 public static bool operator <(YearMonth left, YearMonth right)
107 {
108 return (left.Year < right.Year) || (left.Year == right.Year && left.Month < right.Month);
109 }
110
111 public override bool Equals(object obj)
112 {
113 return base.Equals(obj);
114 }
115
116 public override int GetHashCode()
117 {
118 return base.GetHashCode();
119 }
120 }
其中特性 [JsonConverter(typeof(YearMonthJsonConverter))]用于Json序列化和反序列化。
1 public class YearMonthJsonConverter : JsonConverter<YearMonth>
2 {
3 public override YearMonth Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
4 {
5 return YearMonth.FromString(reader.GetString());
6 }
7
8 public override void Write(Utf8JsonWriter writer, YearMonth value, JsonSerializerOptions options)
9 {
10 writer.WriteStringValue(value.ToString());
11 }
12 }
YearMonth的一些用法示例:
1 var ym = new YearMonth(2023, 2);
2 int n = ym.DaysInMonth(); //n:28
3 DateOnly d1 = ym.FirstDay(); //d1:2023/2/1
4 DateOnly d2 = ym.LastDay(); //d2:2023/2/28
5 string str = ym.ToString(); //str:2023-02
6 YearMonth ym2 = ym.AddMonths(1); //ym2: 2023-03
7 YearMonth ym3 = YearMonth.FromDateOnly(new DateOnly(2023, 2, 8)); //ym3: 2023-02
8 YearMonth ym4 = YearMonth.FromDateTime(new DateTime(2023, 2, 8, 12, 23, 45)); //ym4: 2023-02
9 bool b = new YearMonth(2023, 3) > new YearMonth(2023, 2); //b: true
至此,上面的YearMonth时间类型已经满足小编的开发需要,当然也可以根据需求继续扩展其它功能。