This class is in response to this question:
http://www.codeproject.com/Forums/1649/Csharp.aspx?fid=1649&tid=4084628[
^] . I doubt I'll actually use this code in a
real application, but it was an interesting exercise, perhaps the techniques used will be of interest to others.
This is a static class that spins off a
Thread to perform
System.Console.ReadKey and raise the
KeyPress event as required. Three fields are required: one to hold a reference to the
Thread, one to hold the event handlers, and one to allow locking to avoid threading problems.
namespace PIEBALD.Types
{
public static partial class Consolation
{
private static System.Threading.Thread thread ;
private static System.Windows.Forms.KeyPressEventHandler watchers ;
private static readonly object pickle ;
static Consolation
(
)
{
pickle = new object() ;
thread = null ;
return ;
}
}
}
The only public member is the
KeyPress event; it has custom accessors because add needs to spin off the
Thread when necessary. The
Thread only executes as long as there are handlers attached to the event.
public static event System.Windows.Forms.KeyPressEventHandler
KeyPress
{
add
{
lock ( pickle )
{
watchers += value ;
}
if ( thread == null )
{
thread = new System.Threading.Thread ( DoRead )
{
Priority = System.Threading.ThreadPriority.BelowNormal
,
IsBackground = true
} ;
thread.Start() ;
}
return ;
}
remove
{
lock ( pickle )
{
watchers -= value ;
}
return ;
}
}
The only other member of the class is the
DoRead method that executes on the
Thread as long as there are handlers.
private static void
DoRead
(
)
{
try
{
/* Clear existing characters from the buffer */
while ( System.Console.KeyAvailable )
{
System.Console.ReadKey ( true ) ;
}
while ( true )
{
lock ( pickle )
{
if ( watchers == null )
{
break ;
}
while ( System.Console.KeyAvailable )
{
watchers ( null , new System.Windows.Forms.KeyPressEventArgs
( System.Console.ReadKey ( true ).KeyChar ) ) ;
}
}
System.Threading.Thread.Sleep ( 10 ) ;
}
}
catch
{
/* Just let the thread exit neatly */
}
finally
{
thread = null ;
}
return ;
}
To test the class, I used the following code. It displays the character in c every second until that character is Z, the value of c is updated by the
KeyPress event handler.
public static partial class Template
{
private static char c = ' ' ;
[System.STAThreadAttribute()]
public static int
Main
(
string[] args
)
{
int result = 0 ;
try
{
PIEBALD.Types.Consolation.KeyPress += MyHandler ;
while ( c != 'Z' )
{
System.Console.Write ( c ) ;
System.Threading.Thread.Sleep ( 1000 ) ;
}
}
catch ( System.Exception err )
{
System.Console.WriteLine ( err ) ;
}
finally
{
PIEBALD.Types.Consolation.KeyPress -= MyHandler ;
}
return ( result ) ;
}
private static void
MyHandler
(
object sender
,
System.Windows.Forms.KeyPressEventArgs e
)
{
c = e.KeyChar ;
return ;
}
}
I expect that simply using
System.Console.KeyAvailable and
System.Console.ReadKey would be enough for most real-workd situations, but if you
really want to use events, this code might provide a basis for an implementation.
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