Question

I have a single entity that always duplicate a row when it needs to update:

    protected static Task RegisterToDisc(Task task)
    {         
        try
        {
            using (DataContext context = new DataContext())
            {
                //this will print an actual existing id from the db
                _log.Debug(task.ID);

                context.Tasks.InsertOnSubmit(task);
                context.SubmitChanges();
            }
        }
        catch(Exception e)
        {
           //...
        }
        return task;
    }

When I print the id before the save, it is actually prints out an id that is really exists in the db.

this is the table:

CREATE TABLE [dbo].[TaskSet](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Message] [nvarchar](max) NOT NULL,
    [Result] [nvarchar](max) NOT NULL,
    [Status] [int] NOT NULL,
    [Priority] [int] NOT NULL,
    [Name] [nvarchar](max) NOT NULL,
    [DateTimeAsked] [datetime] NOT NULL,
    [DateTimePerfomed] [datetime] NOT NULL,
    [SessionID] [nvarchar](max) NOT NULL,
 CONSTRAINT [PK_TaskSet] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

Edit

The task is comming from the database already, task.ID contains a number that is exists in the database, how come Linq inserts an entity with PK that is not null and in the db already.

in java hibernate you neet to context.insertOrUpdate(task); and it will decide what to do by the primary key.

Answer 1

InsertOnSubmit always marks the object for insertion. if you want to update the object u need to read it from database like

var objToUpdate = context.Tasks.SingleOrDefault(x=>x.Id == Id);
objToUpdate.Property1 = "updated value";
objToUpdate.Property2 = "updated value";
//do it for all properties that need updating
context.SubmitChanges();//since the object is tracked by context it will automatically generate sql to reflect update in db