sqlite数据读取器

在我的c#应用程序中，我在以下代码中面临问题，用于从数据库中删除项目，

if (orderedRelationSet.RemoveRelation(relation) != true)
{
    TouchServer.Log(Logger.MessageType.Error, 0,     OrderedRelationSet.error_msg + "Remove relation operation failed");
    throw new Exception("remove relation failed");
}

public bool RemoveRelation(Relation relation)
{
    Relation relationToRemove = null;
    relationToRemove = relation;
    int roweffected = 0;
    int flg_delete = 0;
    int ordinal_source = 0;
    if (relationToRemove != null)
    {
        SQLiteDataReader dr_readtype = db.ExecuteSQL("select typeid from item where id=" + relation.ThingId + "");
        try
        {
             dr_readtype.Read();
             type_id = Convert.ToInt32(dr_readtype[0]);
        }
        catch (Exception)
        {
        }
        finally
        {
            dr_readtype.Close();
            dr_readtype.Dispose();
        }
        SQLiteDataReader dr_ordinal = db.ExecuteSQL("select ordinal from relation where parent_itemid=" + relation.SourceThingId + " and child_itemid= " + relation.ThingId + ""); 
        try
        {
            dr_ordinal.Read();
            ordinal_source = Convert.ToInt32(dr_ordinal[0]); 
        }
        catch (Exception)
        {
        }
        finally
        {
            dr_ordinal.Close();
            dr_ordinal.Dispose();
        }

        if (flg_delete == 0 || db.currentUser.UserName=="System")
        {
            relations.Remove(relationToRemove);
            roweffected = relationToRemove.UnSet();
            type_id = 0;
        }
    }
    if (roweffected >= 1)
    {
        SQLiteDataReader dr_ordinal = db.ExecuteSQL("select ordinal,child_itemid from relation where parent_itemid=" + relation.SourceThingId + " and ordinal > " + ordinal_source + ""); 
        Hashtable list = new Hashtable();
        try
        {
            while (dr_ordinal.Read())
            {
                 list.Add(int.Parse(dr_ordinal[1].ToString()), int.Parse(dr_ordinal[0].ToString()));
                 //lis1.Add(int.Parse(dr_ordinal[1].ToString()));
            }
        }
        catch (Exception)
        {
        }
        finally
        {
            dr_ordinal.Close();
            dr_ordinal.Dispose()
        }
        int j = 0;
        foreach (int key in list.Keys)
        {
            int ordi = (int)list[key];
            int ordinal_result = ordi - 1;
            try
            {
                 string sqlExpr = "update relation set ordinal=@ordinal_result where parent_itemid=@relation_SourceThingId and child_itemid=@key";
                 SQLiteCommand _updateRelation = new SQLiteCommand();
                 _updateRelation.CommandText = sqlExpr;
                 _updateRelation.Parameters.AddWithValue("@ordinal_result", ordinal_result);
                _updateRelation.Parameters.AddWithValue("@relation_SourceThingId", relation.SourceThingId);
                _updateRelation.Parameters.AddWithValue("@key", key);
                int update_sql = db.ExecuteNonQuerySQL(_updateRelation);
            }
            catch (Exception)
            {
            }
            j++;
        }
        string sqlExprs = "UPDATE item SET modified =@dates,modifiedby =@currentUser WHERE id =@relation_SourceThingId";
        SQLiteCommand _updateItem = new SQLiteCommand();
        _updateItem.CommandText = sqlExprs;
        _updateItem.Parameters.AddWithValue("@dates", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));
       _updateItem.Parameters.AddWithValue("@currentUser", db.currentUser.id);
       _updateItem.Parameters.AddWithValue("@relation_SourceThingId", relation.SourceThingId);
       int affect = db.ExecuteNonQuerySQL(_updateItem);
       return true;
   }
   else
   {                   
       return false;
   }
   flg_delete = 0;
}

它没有删除数据。。请帮忙。。

    catch (Exception)         {         } 

    catch (Exception E)         
    {
        MessageBox.Show(E.ToString());
    }