Insert Sequential Number in a C #

I have this table called ArticleBarCode :

IntheCodecolumnIneedtoenterasequentialnumber,ieIhavetoreadthemaximumnumberthatisthereandinsertthenextonethatisavailable!Ihavetousethefollowinglineofcodetoseewhattheavailablevalueis:

SELECTISNULL(MAX(Code),0)+1FROMArticleBarCode

Doesanyoneknowhowtohelpwiththissituation?Thanks!

ThisisthecodeIusetoinsertvaluesintothistable:

conn.Open();comm.CommandText=@"INSERT INTO ArticleBarCode(Code, Code_Article, BarCode, CreatedBy, CreatedOn, ModifiedBy, ModifiedOn, IsDeleted)
                                   VALUES (@code, @codearticle, @barcode, 1, @date, 1, @date, 0)";
comm.Parameters.AddWithValue("@code", next);
comm.Parameters.AddWithValue("@codearticle", code);
comm.Parameters.AddWithValue("@barcode", numbercode);
comm.Parameters.AddWithValue("@date", DateTime.Now);
comm.ExecuteNonQuery();
conn.Close();

That next has to be the sequential value! The rest works everything.

I have this code that can fetch the next available value and then try to insert:

 conn.Open();
 SqlCommand cmd5 = new SqlCommand("SELECT ISNULL(MAX(Code), 0) + 1 FROM ArticleBarCode", conn);
 Int32 next = (Int32) cmd5.ExecuteScalar();
 conn.Close();

 conn.Open();
 comm.CommandText = @"INSERT INTO ArticleBarCode(Code, Code_Article, BarCode, CreatedBy, CreatedOn, ModifiedBy, ModifiedOn, IsDeleted)
                    VALUES (@code, @codearticle, @barcode, 1, @date, 1, @date, 0)";
  comm.Parameters.AddWithValue("@code", next);
  comm.Parameters.AddWithValue("@codearticle", code);
  comm.Parameters.AddWithValue("@barcode", numbercode);
  comm.Parameters.AddWithValue("@date", DateTime.Now);
  comm.ExecuteNonQuery();
  conn.Close();

But when I do this, it gives me this error:

  

The INSERT statement conflicts with the FOREIGN KEY constraint   "FK_ArticleBarCode_Article". The conflict occurred in database   "CardozuGestDB", table "dbo.Article", column 'Code'.