c# - 使用 Entity Framework 自动递增主键

Question

我有一个表，我想在不指定 UserID 的情况下向其中插入项目。我希望自动生成此 ID。

CREATE TABLE [dbo].[UserMaster] 
(
    [UserID]       INT           NOT NULL ,
    [UserName]     VARCHAR (50)  NULL,
    [UserPassword] VARCHAR (50)  NULL,
    [UserRoles]    VARCHAR (500) NULL,
    [UserEmailID]  VARCHAR (100) NULL,

    PRIMARY KEY CLUSTERED ([UserID] ASC)
);

这里我尝试通过 C# 插入行:

using (LessonesDBEntities context = new LessonesDBEntities())
{
    var u = new UserMaster//Make sure you have a table called UserMaster in DB
    {
        UserName = "test username",
        UserPassword = "test password",
        UserEmailID = "test email",
        UserRoles = "User"
    };

    context.UserMaster.Add(u);
    context.SaveChanges();
}

但我得到异常:

Violation of PRIMARY KEY constraint 'PK__tmp_ms_x__1788CCACDB8355D2'. Cannot insert duplicate key in object 'dbo.UserMaster'. The duplicate key value is (0). The statement has been terminated.

Answer 1

将 [DatabaseGenerated(DatabaseGeneratedOption.Identity)] 属性添加到您的身份字段 UserId。

public class UserMaster
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }
    public string UserName { get; set; }
    public string UserPassword { get; set; }

    public string UserEmailID { get; set; }
    public string UserRoles { get; set; }
}

当您基于该模型创建迁移和表时，EF 会创建具有自动增量的标识字段。