Question

If I have a multi-layer Winform app with a Presentation, Business and Data Layer for example, and I encounter an error in either the Business Layer or Data Layer for which the only logical action is to log the error and inform the user that an error has occurred where should the logging take place?

Should I put the the methods in the Business and Data Layers in try catch blocks like so

try
{
    DoSomethingThatMightGiveErrors();
}
catch(Exception ex)
{
    logger.log(ex.ToString());
    throw;
}

Or should I just let the errors bubble up to the presentation layer and handle the logging and informing the user there?

Answer 1

I’d put the logging at the business layer level and then rethrow the error. If this layer is used in another project in the future, it’s already doing the logging. Rethrowing the exception allows consumers of this layer to convert the error into a friendly message.

EDIT: I think it depends a bit on the kind of logging: if you’re logging to a central database, which is independent from the UI, put the logging in the business logic layer. If the logging is specific to the UI, for example writing a log file to the application’s directory, put it in the UI.