C# 4 and .NET 4

Building P2P applications ❘ 1349
Event handlers for the ResolveProgressChanged event use the ResolveProgressChangedEventArgs
event arguments parameter, which derives from the standard System.ComponentModel.
ProgressChangedEventArgs class. You can use the PeerNameRecord property of the event argument
object you receive in the event handler to get a reference to the peer name record that was found.
Similarly, the ResolveCompleted event requires an event handler that uses a parameter of type ResolveComplete
dEventArgs, which derives from AsyncCompletedEventArgs. This type includes a PeerNameRecordCollection
parameter you can use to obtain a complete list of the peer name records that were found.
The following code shows an implementation of event handlers for these events:
private pnres_ResolveProgressChanged(object sender,
ResolveProgressChangedEventArgs e)
{
// Use e.ProgressPercentage (inherited from base event args)
// Process PeerNameRecord from e.PeerNameRecord
}
private pnres_ResolveCompleted(object sender,
ResolveCompletedEventArgs e)
{
// Test for e.IsCancelled and e.Error (inherited from base event args)
// Process PeerNameRecordCollection from e.PeerNameRecordCollection
}
After you have one or more PeerNameRecord objects you can proceed to process them. This
PeerNameRecord class exposes Comment and Data properties to examine the comment and data set in the
peer name registration (if any), a PeerName property to get the PeerName object for the peer name record,
and, most importantly, an EndPointCollection property. As with PeerNameRegistration, this property
is a System.Net.IPEndPointCollection collection of System.Net.IPEndPoint objects. You can use
these objects to connect to endpoints exposed by the peer in any way you want.
Code access security in system.net.PeerToPeer
The System.Net.PeerToPeer namespace also includes the following two classes that you can use with
Code Access Security (CAS). See Chapter 21, “Security” for more details.
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PnrpPermission, which inherits from CodeAccessPermission
PnrpPermissionAttribute, which inherits from CodeAccessSecurityAttribute
You can use these classes to provide permissions functionality for PNRP access in the usual CAS way.
sample application
The downloadable code for this chapter includes a sample P2P application (P2PSample) that uses the
concepts and namespace introduced in this section. It is a WPF application that uses a WCF service for a
peer endpoint.
The application is configured with an application configuration file, in which you can specify the name of
the peer and a port to listen on as follows:
code snippet App.config
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