This is a proof of concept of how to bridge an existing ILogger.

Problem

Once I was given a library named ExternalLibrary, I had to add it as a service to the project implementing Dependency Injection. The library has a contructor definition like below

class ExternalLibrary  
{  
 public ExternalLibrary(ILogger<ExternalLibrary> logger, ...);
}

All services in the project had to log with a pre-defined format below. All logs will be pushed to a Serilog’s ElasticSearch sink. Any log does not follow the format, the log consumer will have an issue of parsing it later.

Log.LogInformation("{@ActionGroup} {@ActionTaken}", "GroupA", ActionA");

The problem came when I had to handle log messages from ExternalLibrary but log messages did not follow the pre-defined format. Here is how the log messages from ExternalLibrary were logged:

Log.LogInformation("Begin to fetching...");

Solution

I created a bridge logger injected to ExternalLibrary, it accepted a delegate CustomLogFormatter so that it could modify the format as well as the arguments of all log messages going through it.

The definition of the delegate CustomLogFormatter:

(string, object[]) CustomLogFormatter(string originalFormat, List<object> originalArguments)  
{  
 // ...  
 // Custom implementation  
 // ...  
   
 return (newFormat, newArguments);  
}

The illustration below shows how the bridge logger works.

Source Code

VanDng/BridgeLogger (github.com)

Did I reivent the wheel?

No, I did not want to reinvent the wheel. I did not find a way to solve my problem. If you have a better idea or know a project made to solve the problem already, please share me it. Thank you a lot.