Initiates an asynchronous lookup operation that has a specified state object. This overload receives notification, through a callback, of the identity of the event handler for this operation.
AsyncCallback that will receive the notification of the asynchronous operation completion.The IAsyncResult that identifies the posted asynchronous request.
When you use this overload, the callback specified in the callback parameter is invoked directly when the lookup operation has completed; the LookupCompleted event is not raised. The other overloads of BeginLookup rely on this component to raise the LookupCompleted event.
To use BeginLookup, define an asynchronous callback method. BeginLookup initiates an asynchronous lookup operation; the DnsClient is notified, through a call to the callback method, when the lookup operation is completed. The DnsClient can then access the lookup status by calling EndLookup.
Use this overload to associate information with the operation that will be preserved throughout the operation's lifetime. The event handler can detect this information by looking at the AsyncState of the IAsyncResult that is associated with the operation.
Note: The BeginLookup method returns immediately, but the asynchronous operation is not completed until the event handler is called.
Because BeginLookup is asynchronous, you can call it to receive the lookup status without blocking the current thread of execution. To synchronously lookup, use the Lookup method.
Once an asynchronous operation completes, you can call BeginLookup again in the event handler to keep receiving notifications.
The IAsyncResult that BeginLookup returns identifies the asynchronous operation that the method call started. You can use this IAsyncResult throughout the lifetime of the operation, although you generally do not use it until EndLookup is called. However, if you start several asynchronous operations, you can place their IAsyncResult values in an array and specify whether to wait for all operations or any operation to complete. In this case, you use the AsyncWaitHandle property of the IAsyncResult to identify the completed operation.
The state object associates state information with the operation. For example, if you call BeginLookup multiple times to initiate multiple operations, you can identify each operation through a separate state object that you define.
You can also use the state object to pass information across process threads. If a thread is started but the callback is on a different thread in an asynchronous scenario, the state object is marshaled and passed back along with information from the event.
DnsClient Class | ComponentSpace.Dns Namespace | DnsClient.BeginLookup Overload List