DatabaseGeneratedOption.Identity不生成ID [英] DatabaseGeneratedOption.Identity not generating an Id

问题描述

首先使用EntityFramework代码，我创建了一个简单的Foo表.这是我的实体:

Using EntityFramework code-first, I've created a simple Foo table. Here's my entity:

public class Foo
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public virtual string Id { get; set; }

    public virtual string Name { get; set; }
}

但是，每当我尝试插入新行时，都会得到一个Cannot insert the value NULL into column 'Id'.为什么添加DatabaseGenerated属性时会发生这种情况?删除和重新创建我的表没有任何区别.

However whenever I try to insert a new row, I get a Cannot insert the value NULL into column 'Id'. Why is this happening when I've added a DatabaseGenerated attribute? Deleting and recreating my table makes no difference.

推荐答案

SQL Server不支持string列类型的标识. (您希望这样的字符串看起来如何?)要使其正常工作，您可以-例如-在SQL Server中添加一个计算列/用户定义的函数，该函数可格式化普通int身份列中的字符串-如此处.

Identities for string column types are not supported with SQL Server. (How do you expect such a string to look like?) To get this working you could - for example - add a computed column/user defined function in SQL Server that formats a string from an ordinary int identity column - as shown here.

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