[英]LINQ to SQL exception when attempting to insert a new entry in a database table
I'm trying to insert a user in my database via LINK to SQL and I'm getting an exception: 我试图通过LINK to SQL在我的数据库中插入一个用户,我得到一个例外:
Cannot insert the value NULL into column 'UserID', table 'mydatabase.developer.Users'; 无法将值NULL插入列'UserID',表'mydatabase.developer.Users'; column does not allow nulls. 列不允许空值。 INSERT fails. INSERT失败。 The statement has been terminated. 该语句已终止。
I've marked the UserID as the primary key in my Users table and I was expecting that the SQL Server will automatically generate a PK when I try to insert a new user in the table. 我已将UserID标记为Users表中的主键,并且当我尝试在表中插入新用户时,我预计SQL Server将自动生成PK。
I pretty much copied and pasted the example from Pro ASP.NET MVC Framework Chapter 4 Section on "Setting Up LINQ to SQL." 我几乎复制并粘贴了Pro ASP.NET MVC框架第4章“设置LINQ to SQL”中的示例。 Everything is in order... my database has a Users table with a UserID (PK) column and a Name column (both non-nullable), below is the class corresponding to the database table: 一切都井然有序......我的数据库有一个Users表,其中包含UserID(PK)列和Name列(都是非可空的),下面是与数据库表对应的类:
public class User
{
[DisplayName("User ID")]
[Column(IsPrimaryKey=true, IsDbGenerated=true, AutoSync=AutoSync.OnInsert)]
internal int UserID { get; set; }
[DisplayName("Name")]
[Column]
public string Name{ get; set; }
}
I also have a repository class which allows me to modify the database: 我还有一个存储库类,允许我修改数据库:
public class UsersRepository : IUsersRepository
{
private DataContext database;
private Table<User> usersTable;
public UsersRepository(string connectionString)
{
database = new DataContext(connectionString);
usersTable = database.GetTable<User>();
}
public void AddUser(User user)
{
usersTable.InsertOnSubmit(user);
try
{
database.SubmitChanges();
}
catch (Exception e)
{
var msg = e.Message;
}
}
//...
}
IUsersRepository ur = new UsersRepository(connectionString);
ur.AddUser(new User{Name = "Joe"});
I've also tried setting the UserID to -1, 0 and 1, but I get the same exception! 我也尝试将UserID设置为-1,0和1,但我得到了相同的异常!
ur.AddUser(new User{UserID = -1, Name = "Joe"});
ur.AddUser(new User{UserID = 0, Name = "Joe"});
ur.AddUser(new User{UserID = 1, Name = "Joe"});
Does anybody know what may be happening here? 有谁知道这里可能会发生什么? I'm really baffled by this: what could cause the SQL server not generating the primary key? 我真的很困惑:什么可能导致SQL服务器不生成主键? Is there any way I can inspect the insert statement and verify what is actually being sent to the server? 有什么方法可以检查插入语句并验证实际发送到服务器的是什么?
Is your primary key an integer? 你的主键是整数吗? You need to set the identity specification: 您需要设置标识规范:
If you are using something like a uniqueidentifier, you need to generate on the client with 如果您使用的是uniqueidentifier之类的东西,则需要在客户端上生成
User user = new User();
user.Id = Guid.NewGuid();
Check the properties of the table and make sure UserId allow nulls is set to false; 检查表的属性,并确保UserId允许空值设置为false; make sure auto-increment is set to yes 确保自动增量设置为是
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