Command Execution using the Asynchronous Programming Model

TdCommand supports the Asynchronous Programming Model (APM) of the .NET Framework. This model uses a "Begin" method to start the asynchronous execution, and a corresponding "End" method to finish the execution. The asynchronous methods also make available to applications the following objects that can be used to detect when processing of a request has been completed:

IAsyncResult object: Contains properties that can be used to check for completion (IsCompleted), or wait for completion (AsyncWaitEvent).
Callback Procedures: Delegate is specified as a parameter to the call to the Begin method.

The asynchronous methods will not block when an application sends a request that causes a long-running SQL Engine operation. Once the provider receives the request from an application, it will perform the following tasks before returning control to the application:

Process the parameters
Generate the SQL Engine message
Send the message to the SQL Engine

Once control has returned to the application, it can perform other tasks. One of the following methods can be used to wait for the processing of the request to complete:

Poll on the IAsyncResult.IsCompleted object.
Wait on IAsyncResult.AsyncWaitHandle.
Call the corresponding End method. When this method is called, control will not be returned to the application until processing of the request has completed.
Specify a Delegate in the call to the asynchronous method. Each asynchronous method contains an overload that accepts a delegate. The callback procedure referenced by the delegated is invoked after execution of the command has finished.

The following asynchronous TdCommand methods are supported:

Name	Description
BeginExecuteNonQuery()	Initiates the asynchronous request that is to be submitted to Teradata.
BeginExecuteNonQuery(AsyncCallback, Object)	Overload.
BeginExecuteReader()	Initiates the asynchronous request that is to be submitted to Teradata, and makes one or more result sets available to the application.
BeginExecuteReader(CommandBehavior)	Overload.
BeginExecuteReader(AsyncCallback, Object)	Overload.
BeginExecuteReader(AsyncCallback, Object, CommandBehavior)	Overload.
EndExecuteNonQuery(IAsyncResult)	Finishes the execution of the corresponding BeginExecuteNonQuery.
EndExecuteReader(IAsynchResult)	Finishes the execution of the corresponding BeginExecuteReader.