为什么EF5代码在将可空的日期时间插入数据库时​​首先使用datetime2？

Question

我将Cart对象保存到具有可为空的日期时间的数据库.这是我得到的错误:

将datetime2数据类型转换为日期时间数据类型会导致超出范围的值.

有很多stackoverflow帖子记录了此问题的修复程序.但是,当代码首先创建数据库时,它将创建字段作为DateTime(允许空值).但由于某种原因,代码首先尝试使用DateTime2字段插入.

我想知道为什么EF以单向方式创建字段,但是为同一字段使用不同类型插入.

这是域对象:

using System;
using System.Collections.Generic;

namespace Core.Domain.Cart
{
    public partial class Cart : BaseEntity, ILocalizedEntity
    {
        private ICollection<Catalog> _catalogs;

        /// <summary>
        /// Gets or sets the name
        /// </summary>
        public virtual string Name { get; set; }

        /// <summary>
        /// Gets or sets the zone identifier
        /// </summary>
        public virtual int ZoneId { get; set; }

        /// <summary>
        /// Gets or sets the brand identifier
        /// </summary>
        public virtual int BrandId { get; set; }

        /// <summary>
        /// Gets or sets the customer type identifier
        /// </summary>
        public virtual int CustomerTypeId { get; set; }

        /// <summary>
        /// Gets or sets the date and time of the opening of a cart
        /// </summary>
        public virtual DateTime? OpeningDateUtc { get; set; }

        /// <summary>
        /// Gets or sets the date and time of the closing of a cart
        /// </summary>
        public virtual DateTime? ClosingDateUtc { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether the entity is online or not
        /// </summary>
        public virtual bool IsOnline { get; set; }

        /* Truncated for relevance */
    }    
}

该模型:

using FluentValidation.Attributes;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Web.Mvc;
using Telerik.Web.Mvc;


namespace Admin.Models.Cart
{
        [Validator(typeof(CartValidator))]
        public partial class CartModel : BaseNopEntityModel, ILocalizedModel<CartLocalizedModel>
        {            
            public CartModel()
            {
                Locales = new List<CartLocalizedModel>();
                Catalogs = new List<CatalogModel>();
                UnassociatedCatalogs = new List<CatalogModel>();
            }
            [NopResourceDisplayName("Admin.Carts.Fields.Name")]
            [AllowHtml]
            public string Name { get; set; }

            //Zone dropdown
            [NopResourceDisplayName("Admin.Carts.Fields.ZoneList")]
            public SelectList ZoneList { get; set; }        //The dropdown with zones
            public int ZoneId { get; set; }                 //The selected value of the dropdown once the form is submitted
            public string ZoneName { get; set; }            //The name of the zone to display in data-grid List view.

            //Brand dropdown
            [NopResourceDisplayName("Admin.Carts.Fields.BrandList")]
            public SelectList BrandList { get; set; }       //The dropdown with brands
            public int BrandId { get; set; }                //The selected value of the dropdown once the form is submitted
            public string BrandName { get; set; }           //The name of the brand to display in the data-grid List view. 

            //Customer type dropdown
            [NopResourceDisplayName("Admin.Carts.Fields.CustomerTypeList")]
            public SelectList CustomerTypeList { get; set; }//The dropdown with CustomerType
            public int CustomerTypeId { get; set; }         //The selected value of the dropdown once the form is submitted
            public string CustomerTypeName { get; set; }    //The name of the CustomerType to display in the data-grid List view. 

            [NopResourceDisplayName("Admin.Carts.Fields.OpeningDateUtc")]
            [UIHint("DateNullable")]
            public DateTime? OpeningDateUtc { get; set; }

            [NopResourceDisplayName("Admin.Carts.Fields.ClosingDateUtc")]
            [UIHint("DateNullable")]
            public DateTime? ClosingDateUtc { get; set; }

            [NopResourceDisplayName("Admin.Carts.Fields.IsOnline")]
            public bool IsOnline { get; set; }

            /* Truncated for relevance */
        }

}

所以无论是OpeningDateUtc和ClosingDateUtc的类型为日期时间的？

这是EF代码首先生成数据库的方式:

该OpeningDateUtc和ClosingDateUtc作为一个可空DateTime字段创建.

那么为什么当我使用the保存时IDBContext.SaveChanges(),为查询生成的SQL是:

exec sp_executesql N'update [dbo].[Cart]
set [Name] = @0, [ZoneId] = @1, [BrandId] = @2, [CustomerTypeId] = @3, [OpeningDateUtc] = @4, [ClosingDateUtc] = @5, [IsOnline] = @6, [IsReadonly] = @7, [IsPreviewMode] = @8, [CreatedOnUtc] = @9
where ([Id] = @10)
',N'@0 nvarchar(100),@1 int,@2 int,@3 int,@4 datetime2(7),@5 datetime2(7),@6 bit,@7 bit,@8 bit,@9 datetime2(7),@10 int',@0=N'Cart1',@1=7,@2=4,@3=5,@4='2013-01-09 00:00:00',@5='2013-01-18 00:00:00',@6=0,@7=0,@8=1,@9='0001-01-01 00:00:00',@10=1

有趣的部分是@4 datetime2(7),@5 datetime2(7).

我知道我可以通过添加.HasColumnType("datetime2")到购物车地图来解决这个问题,但它没有回答为什么EF5(可能是旧版本)将它们设置为可以为空的日期时间.

Answer 1

DateTime.NET中的类型与datetime2SQL Server中的类型和精度相同.当EF 在SQL Server中插入或更新一个datetime或一个datetime2列时,它将模型属性转换为可以包含整个DateTime.NET 范围的类型,即datetime2.datetime如果DateTime属性不在datetimeSQL Server 的范围内,转换将失败.

顺便说一下,导致异常的问题不是两个可空OpeningDateUtc和ClosingDateUtc列,而是SQL片段中的CreatedOnUtc值'0001-01-01 00:00:00',即CreatedOnUtc显然未在模型实体中初始化.datetimeSQL Server可以存储的最早日期是在1750年,因此0001年不适合该类型(但它适合datetime2).

因此,解决方案是设置CreatedOnUtc为有效值,datetime或者 - 如您所知 - datetime2在映射中定义类型.

但是我同意,如果EF DateTime默认将属性映射到,那么混淆会更少datetime2.

Answer 2

EF团队在其中一次设计会议中实际讨论了这一特定项目.决定是保持当前行为不变.以下是会议记录,可以为您提供更多背景信息.