在 C# 中将 DateTime 转换为 SmallDateTime
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Converting DateTime to SmallDateTime in c#
提问by kapozade
How can ? convert datetime to smalldatetime in c# ? I'm taking the date and ? need to convert it to be accordance with database. It is forbidden to change the datatype of column in sql.
怎么能 ？在 C# 中将 datetime 转换为 smalldatetime ？我要约会和？需要将其转换为与数据库一致。禁止在sql中更改列的数据类型。
采纳答案by Myk Willis
You can use the .NET DateTimetype for your entity framework model, but tell EF that it uses a non-default column type in the database. You do this by overriding the OnModelCreatingmethod of your DbContext, and using the HasColumnTypemethod:
您可以为实体框架模型使用 .NET DateTime类型，但告诉 EF 它在数据库中使用非默认列类型。您可以通过覆盖DbContext 的 OnModelCreating方法并使用HasColumnType方法来完成此操作：
public class Foo
{
public int Id { get; set; }
public DateTime IAmSoSmall { get; set; } // wants to be smalldatetime in SQL
}
public class MyContext : DbContext
{
public DbSet<Foo> Foos { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
var foo = modelBuilder.Entity<Foo>();
foo.Property(f => f.IAmSoSmall).HasColumnType("smalldatetime");
base.OnModelCreating(modelBuilder);
}
}
Of course, you'll have to do the appropriate range-checking on your DateTime property to be sure that the stored values fall between those supported by SQL's smalldatetime. I guess you could do that with a property attribute like:
当然，您必须对 DateTime 属性进行适当的范围检查，以确保存储的值介于 SQL 的 smalldatetime 支持的值之间。我想你可以用一个属性属性来做到这一点：
[Range(typeof(DateTime), "1/1/1900", "6/6/2079")]
public DateTime IAmSoSmall { get; set; } // wants to be smalldatetime in SQL
...based on a valid range from January 1, 1900, through June 6, 2079, as documented on MSDN.
...基于从 1900 年 1 月 1 日到 2079 年 6 月 6 日的有效范围，如 MSDN 上所述。
回答by user2335149
Maybe you can do something like YourDateTime.Date
也许你可以做一些类似 YourDateTime.Date
Normally, when you do that way, it will set time to 00:00:00.
通常，当您这样做时，它会将时间设置为 00:00:00。
回答by Nicholas Carey
Sql Server datetimeand smalldatetimeare both automaticallymapped to and from the CLR's System.DateTime. A smalldatetimehas a precision of 1 minute; a datetimehas a precision of approximately 1/300 of a second (Don't ask why. It just is). Since the CLR's System.DateTime1has a precision of 100-nanoseconds, the runtime takes care of rounding.
Sql Serverdatetime并且smalldatetime都自动映射到 CLR 的System.DateTime. Asmalldatetime的精度为 1 分钟；adatetime具有大约 1/300 秒的精度（不要问为什么。它就是这样）。由于 CLR 的System.DateTime1精度为 100 纳秒，因此运行时负责舍入。
smalldatetimeis internally a 32-bit integer, containing a count of minutes since thesmalldatetimeepoch (1900-01-01 00:00).In conversion, seconds and fractional seconds are rounded using SQL Server's arcane date/time rounding rules, so the date 2013-01-31 23:59:59 gets rounded to the next date 2013-02-01 00:00:00'.
datetimeis a pair of 32-bit integers internally. The high-order word is a count of days since the epoch; the low-order word is a count of milliseconds since start-of-day (00:00:00). The epoch of adatetimeis 1900-01-01 00:00:00.000.And again, values are rounded in the conversion in the same arcane way, with franctional seconds getting placed into one of the appropriate millisecond buckets for SQL Server, a multiple of 3ms — there is no SQL Server `datetime value like 2013-05-01 13:57:23.004. That will get "rounded" to either 23.003ms or 23.006ms.
smalldatetime内部是一个 32 位整数，包含自smalldatetime纪元 (1900-01-01 00:00)以来的分钟数。在转换中，秒和小数秒使用 SQL Server 的神秘日期/时间舍入规则舍入，因此日期 2013-01-31 23:59:59 被舍入到下一个日期2013-02-01 00:00:00'。
datetime内部是一对 32 位整数。高位词是自纪元以来的天数；低位字是自一天开始 (00:00:00) 以来的毫秒数。a 的纪元datetime是 1900-01-01 00:00:00.000。再次，值在转换中以同样神秘的方式四舍五入，小数秒被放置到 SQL Server 的适当毫秒桶之一中，3ms 的倍数 - 没有像 2013-05-01 这样的 SQL Server `datetime 值13:57:23.004。这将“四舍五入”到 23.003 毫秒或 23.006 毫秒。
If you want more control over things, you'll need to adjust your datetime values in C# before sending them to the database.
如果您想对事物进行更多控制，则需要在将它们发送到数据库之前在 C# 中调整日期时间值。
