SQL列默认值与实体框架 [英] SQL column default value with Entity Framework

问题描述

我试图使用默认SQL值的Code-First EF6。

I am trying to use Code-First EF6 with default SQL values.

例如，我有一个CreatedDate列/属性not null，SQL中的默认值为getdate（）

For example, I have a "CreatedDate" column/property not null with a default in SQL of "getdate()"

如何在我的代码模型中代表这个？目前我有：

How do I represent this in my code Model? Currently I have:

<DatabaseGenerated(DatabaseGeneratedOption.Computed)>
Public Property CreatedDate As DateTime

这是否工作，或者我需要使用可空即使实际的列不应该为空，所以当EF未设置时，EF不会发送一个值：

Will this work, or will I need to use a nullable even though the actual column should be not null, so EF doesn't send a value when it hasn't been set:

<DatabaseGenerated(DatabaseGeneratedOption.Computed)>
Public Property CreatedDate As DateTime?

还是有更好的解决方案？

Or is there a better solution out there?

我不希望EF处理我的默认值 - 我知道这是可用的，但我目前的情况是不可能的。

I don't want EF to handle my defaults - I know this is available to me but not possible in my current situation.

推荐答案

目前在EF6中没有定义用于特定属性默认值的数据库函数的属性。您可以对Codeplex进行投票，以实现它：

Currently in EF6 there is not an attribute to define database functions used for a certain property default value. You can vote on Codeplex to get it implemented:

https：// entityframework .codeplex.com / workitem / 44

实现类似的方法是使用计算的属性与迁移您指定默认数据库函数。

The accepted way to implement something like that is to use Computed properties with Migrations where you specify the default database function.

您的课程可能在C＃中看起来像这样：

Your class could look like this in C#:

public class MyEntity
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public DateTime Created { get; set; }
}

计算的属性不必为空。

然后您必须运行迁移并手动修改它以包括默认的SQL函数。迁移可能如下所示：

Then you have to run a migration and modify it by hand to include the default SQL function. A migration could look like:

public partial class Initial : DbMigration
{
    public override void Up()
    {
        CreateTable(
            "dbo.MyEntities",
            c => new
                {
                    Id = c.Int(nullable: false, identity: true),
                    Name = c.String(),
                    Created = c.DateTime(nullable: false, defaultValueSql: "GetDate()"),
                })
            .PrimaryKey(t => t.Id);

    }

    public override void Down()
    {
        DropTable("dbo.MyEntities");
    }
}

您将注意到defaultValueSql函数。这是获得计算工作的关键

You will notice the defaultValueSql function. That is the key to get the computation working

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