First we need to know what application blocks
are. Application Blocks are reusable software components and are part of
Microsoft's Enterprise Library. The enterprise library provides configurable
features to manage crosscutting concerns like validation, logging, exception
management etc. Here I elaborate on one of the feature of the Enterprise Library-
Logging Application Block. One can use the Logging Application Block to log
- Event logs
- A text file
- An email message
- A database
- A message queue
- Windows Management Instrumentation (WMI) event
- Customize the logging location
Create a windows form application. Now add a
reference to Enterprise Library Logging Application Block to the solution.
Now add a configuration file for configuring the log. Now edit it with the Enterprise Library Configuration.
It opens a window. In that select Blocks -> Add Logging Settings
It creates a default logging settings as follows:
It contains a category named "General", which is using an "Event Log Listener"
with a "Text Formatter". For now we can leave Special Categories. So, what all
these are doing?
Let's understand it with an example. There may be some logs which you need to
write in event log and a text file, and for some log you need to mail also. So
you create one category which writes all logs to event log and text file, and
another category for sending mail of only error logs. Then you have to create 3
listeners, for logging in event log, text file and mailing. You can also define
different formatters for different type of listeners. For example you need a
detailed log for logging in events log and precise log for mailing. All these
settings are defined in the configuration. All you need to do is when you write
a log just defines the category of the log and rest is done by the application
Category can filter the log entry and route it to different listeners. The
filter can be based on the severity, i.e., Critical, Error, Warning or
Logging Target Listeners:
Different listeners can be defined here. We only need to do configuration and
these listeners can write to event logs, a flat file, xml file, to database,
send mail etc.
Log Message formatters:
This is used to define a format in which the log is written. Text formatter is the
default formatter, which writes all the information. For customizing the
formatter, define a template.
A sample project was uploaded. This contains a general category which logs to
event logs and a flat file using text formatter. And mail category which sends
mail using mail formatter. And depending on the conditions it logs to general
category, or sends mail, or can do both.
So now you can see a configuration section called "loggingConfiguration" in the
This configuration section contains listeners, formatters, categorysources and
specialSources. One can configure listener, formatter, categories here.
To write a log you just need to create a LogEntry and specify the category. Of
category is not specified, log will be written to default category.
So, now you can see logging is so easy using Application blocks.