Why can't I update data into database using LINQ to SQL?

Question

I am trying to update data while I am reading them from database, see below. But after the whole thing finish, the data didn't get updated.

Is there any transaction syntax i need to specify? (When I debug, I can see I have the right record retrieved.)

using (conn = new SqlConnection(MyConnectionString))
                using (SqlCommand cmd = new SqlCommand("dbo.MyProcedure", conn))
                {
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.AddWithValue("@Count", count);
                    conn.Open();
                    using (SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
                    {
                        while (reader.Read())
                        {
                            // wrapper object, not related to database
                            SampleModel c = new SampleModel();  
                            c.ID= (string)reader["ID"];
                            c.Name = (string)reader["Name"];
                            c.Type = (int)reader["Type"];

                            // modeList will return to outside, not related to database
                            modelList.Add(c);

                            sampleTable1  table1 = context.sampleTable1s.SingleOrDefault(t=> t.id = c.ID);   

                            // try to update the "isRead", but it doesn`t work....!!!
                            // about the datatype, in the data base, it is "smallInt"
                            // in linq to sql, it is "short?"
                            // PS Default value all should be 0
                            table1.isRead = 1;
                            context.SubmitChanges();  <--- here, it doesn`t do the job // context is new from Linq to SQL
                        }
                    }
                    conn.Close();
                }

Here is my procedure:

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE MyProcedure    
    @Count int = 100
AS
BEGIN

  SELECT TOP (@Count )
         t1.id AS ID, 
         t1.name AS Name, 
         t2.type AS TYPE    
    FROM sampleTable1 as t1 with (nolock), 
         sampleTable2 as t2 with (nolock)          
   WHERE (t1.t2Id = t2.Id)     
ORDER BY t1.name asc

END
GO

And if I put all my code inside TransactionScope block

using (TransactionScope scope = new TransactionScope())
{
    // all the C# code above
    scope.Complete();
}

I will get an exception "MSDTC on server 'localhost-sqlserver2005' is unavailable."

And if I only put some of the code, there is no exception, but the data did`t get updated

using (TransactionScope scope = new TransactionScope())
{
    sampleTable1  table1 = context.sampleTable1s.SingleOrDefault(t=> t.id = c.ID);   

    table1.isRead = 1;
    context.SubmitChanges(); 

    scope.Complete();
}

Thanks.

Answer 1

Check so at least one member in the entity class in question is marked as as primary key member in the L2S designer. If an entity doesn't have any PK members, L2S will silently ignore it when submitting updates (silently as in no exception thrown, and no update SQL statement generated and sent to db).

Answer 2

Make sure you have the primary key set for that table. If you can't do that in the db, do it in the linq2sql designer.

Answered this here, here and here. Also mentioned it linq to sql pitfalls.