c# data matrix generator TRANSACTIONS in C#

Encoder Data Matrix ECC200 in C# TRANSACTIONS

Figure 12-1. A set of tables to update within a transaction So for the sample scenarios, your transaction will be composed of the following steps: 1. Create a new order for the customer in the order table 2. For each order item, decrease the on-hand amount for the item by the quantity being ordered. 3. Audit the attempt to secure the quantity. 4. Create an order item for the order. If there is not enough on hand for any item in the order, then the transaction should roll back. However, the audits should succeed whether the order is created or not. Here s the method to create the order. (See XAction.cs in the App_Code directory of the Web12 project.) public void AddOrder(int orderId, int customerID, DateTime orderDate) { using (TransactionScope tx = new TransactionScope(TransactionScopeOption.Required)) { string sql = "INSERT INTO [Order](OrderID, CustomerID, OrderDate) " + "VALUES (@orderID, @customerID, @orderDate)"; SqlConnection cn = new SqlConnection(connStr); SqlCommand cm = new SqlCommand(sql, cn); cm.Parameters.Add(new SqlParameter("@orderId", SqlDbType.Int)).Value = orderId; cm.Parameters.Add(new SqlParameter("@customerID", SqlDbType.Int)).Value = customerID; cm.Parameters.Add(new SqlParameter("@orderDate", SqlDbType.DateTime)).Value = orderDate;

cn.Open(); cm.ExecuteNonQuery(); cn.Close(); tx.Complete(); } } The method to create a new order item follows (also in XAction.cs in the App_Code directory of the Web12 project). public bool AddOrderItem(int orderId, int itemId, int quantity) { using (TransactionScope tx = new TransactionScope(TransactionScopeOption.Required)) { if (UpdateQuantity(itemId, quantity)) { string sql = "INSERT INTO OrderItem(OrderID, InventoryID, Quantity) " + "VALUES (@OrderID, @InventoryID, @Quantity)"; SqlConnection cn = new SqlConnection(connStr); SqlCommand cm = new SqlCommand(sql, cn); cm.Parameters.Add(new SqlParameter("@OrderID", SqlDbType.Int)).Value = orderId; cm.Parameters.Add(new SqlParameter("@InventoryID", SqlDbType.Int)).Value = itemId; cm.Parameters.Add(new SqlParameter("@Quantity", SqlDbType.Int)).Value = quantity; cn.Open(); cm.ExecuteNonQuery(); cn.Close(); tx.Complete(); return true; } else return false; } } Notice the first thing that this method does after enlisting in the transaction is to call the UpdateQuantity method (listed previously). If this method fails, it means you re out of stock on the item being ordered, and so this method will not create the order item. It also does not call Complete in this case, which in effect dooms the entire transaction. UpdateQuantity is what

calls for the audit. The code creating the entry in the audit table follows (also in XAction.cs in the App_Code directory of the Web12 project). public void AuditItemUpdate(int itemId, int quantity) { using (TransactionScope tx = new TransactionScope(TransactionScopeOption.RequiresNew)) { string sql = "INSERT INTO InventoryAudit(InventoryID, Quantity, AttemptDate) " + "VALUES (@InventoryID, @Quantity, @AttemptDate)"; SqlConnection cn = new SqlConnection(connStr); SqlCommand cm = new SqlCommand(sql, cn); cm.Parameters.Add(new SqlParameter("@InventoryID", SqlDbType.Int)).Value = itemId; cm.Parameters.Add(new SqlParameter("@Quantity", SqlDbType.Int)).Value = quantity; cm.Parameters.Add(new SqlParameter("@AttemptDate", SqlDbType.DateTime)).Value = DateTime.Now; cn.Open(); cm.ExecuteNonQuery(); cn.Close(); tx.Complete(); } } Here you ll notice that the transaction option selected when creating the TransactionScope instance is RequiresNew. This breaks the work done in this method out into its own transaction. Since you want the audit to persist regardless of the outcome of the containing transaction, this work is done independent from the transaction of the caller. Using TransactionOption.Suppress would have the some effect, except the work done within this method would occur without a transaction at all. The entire transaction is then managed by this orchestration method, which gets handed a hash table of inventory IDs and quantities. (See XActionHost.aspx in the Web12 project.) private void PlaceOrder(int CustomerID, DateTime OrderDate, Hashtable OrderItems) { XAction dalTx = new XAction(); int OrderId = GetNextOrderID(); bool bSuccess = true; using (TransactionScope tx = new TransactionScope()) { dalTx.AddOrder(OrderId, CustomerID, DateTime.Now); foreach(int ItemId in OrderItems.Keys)

{ if (!dalTx.AddOrderItem(OrderId, ItemId, Convert.ToInt32(OrderItems[ItemId]))) { bSuccess = false; break; } } if (bSuccess) tx.Complete(); } if (bSuccess) { lblOutput.Text = "Success"; } else { lblOutput.Text = "Rolled back"; } } This is what you could call the root transaction object in COM+. It s the root of the call stack for the entire transaction. All of the work at lower levels in the stack is enlisted within the transaction created by this method (with the exception, of course, of the audit method, which declares its need for a transaction of its own). The entire call stack breaks down like this (see Figure 12-2).