Logging messages in a class based on who is using it...?

[JohnW]

Hi,
I'm not sure of the terminology here but...

I have a standalone assembly (Foo) and I log errors using a simple call
in my "catch" blocks: e.g.

class Foo
....
public DoSomething()
{
....
catch
{
LogError("blah", Severity.Error, etc....);
}
....
void LogError(msg,sev,...) { output.write(...) }
....
This assembly DLL will be referenced by other assemblies however each
of these calling assemblies may wish to log any errors their own way.
Can I make it so that the calling assembly somehow "overrides" the
LogError calls and writes the errors however it wishes. Ideally I'd
like:

using Foo
class Bar
....
Foo.DoSomething()
....
void LogError(msg) { showpopup(msg) } <--(I want THIS LogError to run
when DoSomething goes wrong)


I'm looking at interfaces, abstract classes, virtual functions, etc.
but I'm not inherting anything here - just making calls to an assembly.

Hope someone can help.

Thanks.

 

[Michael Nemtsev]

Hello JohnW,

A bit off-top, why do u want to use your own logger?
There are already a lot of nice realiziation of loggers - MS Enterprise,
log4net.

J> Hi,
J> I'm not sure of the terminology here but...
J> I have a standalone assembly (Foo) and I log errors using a simple
J> call in my "catch" blocks: e.g.
J>

---
WBR,
Michael Nemtsev :: blog: http://spaces.msn.com/members/laflour

"At times one remains faithful to a cause only because its opponents do not
cease to be insipid." (c) Friedrich Nietzsche

 

[JohnW]

Hi,
Well that's the thing - I want calling apps to be able to use those
loggers if they want to. My own logger is just basic.

Thanks.

 

[John Wood]

You could probably pass in the 'this' pointer to the log call, and have the
logging method check in the passed-in object for a specific interface, or
look for a specific class name in its assembly (or class with a specific
attribute) that will provide the overridden logging functionality. If it
doesn't find it, it just falls back to default behavior of writing to that
file. That's the least intrusive solution I can think of right now.

 

[=?iso-8859-1?Q?Anders=20Nor=e5s?=]

You can use an event to allow client code to be notified whenever something
needs to be logged.
The example below shows a naïve implementation of this. You'll have to write
your own EventArgs implementation to contain the information to be logged.
public class MyClass
{
public void MyMethod()
{
try
{
throw new ApplicationException("Something went wrong");
}
catch
{
OnLog(new EventArgs());
}
}
private void OnLog(EventArgs e)
{
if (Logging!=null)
{
Logging(this,e);
}
}
public event LoggingEventHandler Logging;
public delegate void LoggingEventHandler(object sender, EventArgs e);
}

Anders Norås
http://dotnetjunkies.com/weblog/anoras/