/// <summary>
/// Execute the batch and catch the errors.
/// </summary>
/// <param name="batch">A batch of commands to be executed.</param>
/// <returns>Any exceptions from executing the batch, null if there are none.</returns>
public static bool Execute(Batch batch, Control owner, BatchExceptionEventHandler batchExceptionEventHandler)
{
bool success = false;
// Execute the batch and process the results.
if (batch != null)
{
success = true;
try
{
// Execute the batch on the server and process the results.
ClientMarketData.Execute(batch);
}
catch (BatchException batchException)
{
success = false;
owner.BeginInvoke(batchExceptionEventHandler, new object[] { typeof(ClientMarketData),
new BatchExceptionEventArgs(batchException) });
}
}
return(success);
}
/// <summary>
/// Event trigger when any record in the data model has changed.
/// </summary>
/// <param name="sender">Object originating the event.</param>
public static void OnEndMerge(object sender)
{
// If a handler has been associated with this event, invoke it.
if (ClientMarketData.EndMerge != null)
{
ClientMarketData.EndMerge(sender, EventArgs.Empty);
}
}
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
System.Resources.ResourceManager resources = new System.Resources.ResourceManager(typeof(AdvertisementViewer));
this.clientClientMarketData = new MarkThree.Guardian.Client.ClientMarketData(this.components);
this.SuspendLayout();
//
// AdvertisementViewer
//
this.Name = "AdvertisementViewer";
this.ResumeLayout(false);
}
/// <summary>
/// Execute a command batch and synchronizes the client data model with the newer records from the server.
/// </summary>
public static void Execute(Batch batch)
{
// This 'try' block will insure that the mutual exclusion locks are released.
try
{
// Make sure only one thread at a time tries to refresh the data model.
ClientMarketData.clientDataMutex.WaitOne();
// Switching credentials without exiting the application will force the data model to be cleared and the row
// counting to begin at zero again. That is, it effectively resets the client data model.
if (ClientMarketData.isReset)
{
ClientMarketData.isReset = false;
ClientMarketData.rowVersion = 0;
ClientMarketData.Clear();
}
// IMPORTANT CONCEPT: The rowVersion keeps track of the state of the client in-memory database. The server
// returns a value for us to use on the next cycle.
long rowVersion = ClientMarketData.rowVersion;
// IMPORTANT CONCEPT: Executing the 'GetClientMarketData' with a rowVersion returns to the client a DataSet
// with only records that are the same age or younger than the rowVersion. This reduces the traffic on the
// network to include only the essential records. We are also merging it with the current ClientMarketData,
// which adds new records and records that were deleted by the server.
AssemblyPlan assembly = batch.Assemblies.Add("Server Market Data");
TypePlan type = assembly.Types.Add("MarkThree.Guardian.Server.ServerMarketData");
TransactionPlan transaction = batch.Transactions.Add();
MethodPlan method = transaction.Methods.Add(type, "Reconcile");
Parameter rowVersionParameter = method.Parameters.Add(new InputParameter("rowVersion", rowVersion));
// Execute the the command to get the incremental changes from the server.
WebTransactionProtocol.Execute(batch);
// This is the updated data model information returned from the server.
ArrayList reconciledData = (ArrayList)method.Parameters.Return.Value;
// Optimization: Don't merge the results if there's nothing to merge.
if (reconciledData != null)
{
// IMPORTANT CONCEPT: Since the results will still be on the server if the client misses a refresh
// cycle, we take the attitude that thBzis update process doesn't have to wait for locks. That is, if we
// can't get all the tables locked quickly, we'll just wait until the next refresh period to get the
// results. This effectively prevents deadlocking on the client. Make sure all the tables are locked
// before populating them.
foreach (TableLock tableLock in ClientMarketData.TableLocks)
{
tableLock.AcquireWriterLock(ClientTimeout.LockWait);
}
// IMPORTANT CONCEPT: This broadcast can be used to set up conditions for the data event handlers. Often,
// optimizing algorithms will be used to consolidate the results of a merge. This will allow the event
// driven logic to clear previous results and set up initial states for handling the bulk update of data.
ClientMarketData.OnBeginMerge(typeof(ClientMarketData));
// IMPORANT CONCEPT: Once all the write locks have been obtained, we can merge the results. This will
// trigger the events associated with the tables for updated and deleted rows. Note that this 'Merge'
// method has different characteristics than the original one provided by Microsoft (that is, this one
// works).
ClientMarketData.rowVersion = MarketData.Merge(reconciledData);
// IMPORTANT CONCEPT: When the merge is complete, this will broadcast an event which allows optimization code
// to consolidate the results, examine the changed values and update reports based on the changed data.
ClientMarketData.OnEndMerge(typeof(ClientMarketData));
}
}
finally
{
// No matter what happens above, we need to release the locks acquired above.
foreach (TableLock tableLock in ClientMarketData.TableLocks)
{
if (tableLock.IsWriterLockHeld)
{
tableLock.ReleaseWriterLock();
}
}
// Other threads can now request a refresh of the data model.
ClientMarketData.clientDataMutex.ReleaseMutex();
}
// Throw a specialized exception if the server returned any errors in the Batch structure.
if (batch.HasExceptions)
{
throw new BatchException(batch);
}
}
