23502: null value in column "id" violates not-null constraint in postgreSQL - postgresql

Question

I create a table with primary key.
I tried to insert new data with entityframework6, but it would get 23502 error.
But I add the default value to the column before I insert it.
I don't understand why it would get this error.
Table DDL:
CREATE TABLE ERRORLOG(
id numeric NOT NULL,
message varchar(50) NULL,
CONSTRAINT pterrorlog_pk PRIMARY KEY (id)
);
Model:
public partial class ERRORLOG
{
[Key]
[Column(Order = 0)]
public long ID { get; set; } = DateTimeOffset.Now.ToUnixTimeMilliseconds();
public string MESSAGE { get; set; }
}
Funcation:
using (DbContext Db as new DbContext)
using (TransactionScope transactionScope = new TransactionScope())
{
ERRORLOG iLog = new ERRORLOG();
iLog.MESSAGE = Message;
Db.ERRORLOG.Add(iLog);
Db.SaveChanges(); //Get 23502 error
}
Here is the insert script, it looks like didn't insert the id, why is that?
INSERT INTO "pterrorlog"("message") VALUES (#p_0) RETURNING "id"
Edit:
After I add this script on the Model, it works fine now.
public partial class ERRORLOG
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public long ID { get; set; } = DateTimeOffset.Now.ToUnixTimeMilliseconds();
public string MESSAGE { get; set; }
}

Answer 1

Looks like Entity Framework auto insert a value to the column.
After I add the script to prevent this issue, it works fine now.
[DatabaseGenerated(DatabaseGeneratedOption.None)]
Model would like:
public partial class ERRORLOG
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public long ID { get; set; } = DateTimeOffset.Now.ToUnixTimeMilliseconds();
public string MESSAGE { get; set; }
}

Answer 2

You can use PGAdmin to profile the SQL that EF is actually attempting to execute on SaveChanges. C# is case sensitive while Postgres defaults to lower case. If I recall NPGSQL will format all EF SQL Queries with double-quotes so if your Entities were declared with properties like ID, it would be generating statements like INSERT INTO "ERRORLOG" ( "ID", "MESSAGE" ) VALUES ( ... ) so a column named "id" wouldn't be getting set.
If you want your entities to use a different case than the DB, and leave Postgres using lower case then I'd recommend using [Column] attributes to rename the columns:
public partial class ERRORLOG
{
[Key, Column(Name = "id")]
public long ID { get; set; } = DateTimeOffset.Now.ToUnixTimeMilliseconds();
[Column(Name = "message")]
public string MESSAGE { get; set; }
}
The other detail is that Order on the Column attribute is only needed when dealing with composite keys, such as many-to-many joining tables where the PK is made up of two or more columns. It isn't needed for normal single-value PKs.
If that isn't the cause, checking the insert statement in PGAdmin should give you a clue what NPGSQL / EF is attempting to execute.