ContextProviders.md

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Context Providers

By implementing the RockLib.Logging.IContextProvider interface, defining the AddContext method, and providing it to a Logger, you are able to automatically modify a LogEntry whenever it is written to its destination.

The following implementation of IContextProvider will add the version of the operating system (OS) under which the application is running as an extended property to any LogEntry emitted by the logger:

   public class OsContextProvider : IContextProvider
    {
        public void AddContext(LogEntry logEntry)
        {
            logEntry.SetExtendedProperties(new {OSVersion = System.Environment.OSVersion.VersionString});
        }
    }

Context providers are passed to the Logger upon instantiation via an array of type IContextProvider. For example, the following code will provide a new instance of the above context provider to a new Logger:

var logger = new Logger(contextProviders: new [] { new OsContextProvider() });

Alternatively, context providers can be assigned to a Logger by means of configuration. In the following example, we will assign our context provider to the default Logger:

{
  "RockLib.Logging": {
    "LogProviders": {
        "Type": "RockLib.Logging.ConsoleLogProvider, RockLib.Logging"
    },
    "ContextProviders": {
        "Type": "MyProject.OsContextProvider, MyProject"
    }
  }
}