使用UniqueIdentifier列类型和[DatabaseGenerated（DatabaseGeneratedOption.Identity）]对于模型的键在EF代码中不起作用 [英] Use UniqueIdentifier column type and [DatabaseGenerated(DatabaseGeneratedOption.Identity)] for model's key doesn't work in EF Code First

问题描述

这是我的MVC模型：

public class Link
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid ID { get; set; }

    [DisplayName("Shorted URL")]
    public string SURL { get; set; }

    [DisplayName("General Link")]
    public string OriginalURL { get; set; }

    [DisplayName("Click Count")]
    public int ClickCount { get; set; }
}

这是 LinkDBContext class：

public class LinkDBContext : DbContext
{
    public DbSet<Link> Links { get; set; }
}

when I want to add some data to database using this code:

    private string GetNewID(string url, string id)
    {
        LinkDBContext Links = new LinkDBContext();
        //id = "http://" + id;
        List<Link> link = Links.Links.Where(a => (a.OriginalURL == id && a.SURL == id)).ToList();
        if (link.Count == 0)
        {
            List<Link> LLinks = Links.Links.ToList<Link>();
            Link li = new Link();
            //li.ID = new Guid();
            li.ClickCount = 0;
            li.SURL = id;
            li.OriginalURL = url;
            Links.Links.Add(li);
            Links.SaveChanges();
            Links.Dispose();
            return id.ToString();
        }

        return GetNewID(url);
    }

我只得到一个异常：将值NULL转换为列'ID'，表'GhiasiDB.dbo.Links';列不允许空值。 INSERT fails.The语句已终止。

I just get an exception that is: Cannot insert the value NULL into column 'ID', table 'GhiasiDB.dbo.Links'; column does not allow nulls. INSERT fails.The statement has been terminated.

问题是什么，如何解决？

what is the problem and how can I resolve it?

更新

我更改了 ID 从 Guid 到 int 列表< Link> LLinks = Links.Links.ToList< Link>（）; GetNewID 方法：链接无法设置为Guid值。您必须将此属性设置为类型Int32的非空值。
，我不知道它来自哪里。我将所有 Guid es改为 int ！

I changed the type of ID from Guid to int and when I tried again I got this exception from List<Link> LLinks = Links.Links.ToList<Link>(); of GetNewID method:The 'ID' property on 'Link' could not be set to a 'Guid' value. You must set this property to a non-null value of type 'Int32'. and I don't know where did it come from. I changed all Guides to int!

推荐答案

如果允许EF生成表，它将创建一个默认值设置为（newid（））的PK。如果您先设计数据库，可以手动设置。

If you allowed EF to generate the tables it would create the PK with a default value set to (newid()). You can set it manually if you designed the database first.

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