Reacting to events

Events in .NET occur when something of interest happens to an object. For instance, System.IO.FileSystemWatcher can be used to monitor a file system for changes; when something changes, an event will be raised.

Many different types of objects raise events when changes occur. Get-Member can be used to explore an instance of an object for Event members. For example, a Process object returned by the Get-Process command includes several events, shown as follows:

PS> Get-Process | Get-Member -MemberType Event
   TypeName: System.Diagnostics.Process
Name               MemberType Definition
----               ---------- ----------
Disposed           Event      System.EventHandler Disposed(Syst...
ErrorDataReceived  Event      System.Diagnostics.DataReceivedEv...
Exited             Event      System.EventHandler Exited(System...
OutputDataReceived Event      System.Diagnostics.DataReceivedEv...

PowerShell can react to these events, executing code when an...