Using Serilog with configuration from appsettings.json

[StevenBoelens]

Hi,

is it possible to use the Uno platform with Serilog logging and configure the sinks using configuration in the Serilog section of appsettings.json?
Does someone have an example that shows how to set this up?

My app is for desktop platforms only (Mac, Windows, Linux) and uses skia, MVVM and of course Serilog.

In another solution (not Uno platform) I already use Serilog with the following configuration in appsettings.json.

  // Logging configuration
  "Serilog": {
    "MinimumLevel": {
      // Default logs anything of severity Debug and higher.
      "Default": "Debug"
    },

    "WriteTo": [
      // Log expression to log anything to the console.
      {
        "Name": "Console",
        "Args": {
          "formatter": {
            "type": "Serilog.Templates.ExpressionTemplate, Serilog.Expressions",
            "template": "{@t:HH:mm:ss} {@l:u3} {Coalesce(Substring(SourceContext, LastIndexOf(SourceContext, '.') + 1), 'Application'), -30} {@m}\n{@x}",
            "theme": "Serilog.Templates.Themes.TemplateTheme::Code, Serilog.Expressions"
          }
        }
      },

      // Log expression to log anything with severity warning or higher to a seperate err_.txt file.
      {
        "Name": "Logger",
        "Args": {
          "configureLogger": {
            "Filter": [
              {
                "Name": "ByIncludingOnly",
                "Args": {
                  "expression": "(@l = 'Error' or @l = 'Fatal' or @l = 'Warning')"
                }
              }
            ],
            "WriteTo": [
              {
                "Name": "File",
                "Args": {
                  "path": "logs/Myapp-err-.log",
                  "rollingInterval": "Day",
                  "outputTemplate": "[{Timestamp:HH:mm:ss} {SourceContext}]{NewLine}{Message:lj}{NewLine}{Exception}"
                }
              }
            ]
          }
        }
      }
    ]
  },

Regards,
Steven.

[DevTKSS]

Hello @StevenBoelens ,
First of all: Happy New Year 2026! 🎉

Now to your Question about using Serilog usage in Uno Projects:

Indeed, Serilog is my preferred Logging kind in one of my Repos: https://github.com/DevTKSS/DevTKSS.MyManufacturerERP

• appsetting.json Reference from my Uno Client in there, which is primary targeting Desktop, but includes also the other targets except from Windows, because of [DataTemplate][Windows] Property Not Found Exception at Styles/Generic.xaml #19977
• Uno Wasm "Server" initial provided by the Uno Extension Wizard but meanwhile updated with the (from Serilog) recommended Logging Setup using CreateBootstrapLogger(...), which is (just like the appsettings.json section itself) so far not provided by the Uno.Templates too.

Added Links on this Uno.Templates Repo Issue about the missing appsettings*.json in our Templated Uno Apps:

• [Bug] Serilog + Configuration Templated app does not include initial Serilog Config section uno.templates#1756

I hope they will check the other Problems filed there too, because fun-fact: from what I see Uno doing:

• in Uno.Extensions.Logging.Serilog/HostbuilderExtensions.cs AddConsoleLogging + AddFileLogging, as soon as you are setting consoleLoggingEnabled = true or fileLoggingEnabled in the UseSerilog() Hostbuilder Extension, they will just silently override your ExpressionTemplate.Template for Console Logging and if you would use Android / iOS, also for FileLogging. 🤔 It's just my opinion, but I do not find this very nice...

Or how would you read this calling those seperate functions? Maybe I am just blind... 👀

https://github.com/unoplatform/uno.extensions/blob/9e1337c5d07679dba1c31a0324a4d9ca5993d45b/src/Uno.Extensions.Logging.Serilog/HostBuilderExtensions.cs#L59-L92

From what I understand, if I would do this in my code:

1. get a Configuration from the appsettings*.json
2. use loggerConfiguration.WriteTo.Console(...) or whatever Platform specific logger call, because if they would even consider checking if we might had provided a template already, it would be okay, to execute this if we not did this! 🤔
3. use loggerConfiguration.WriteToFile(logFilePath, outputTemplate: ...), where logFilePath is silently also overridden from GetLogFilePath internally, which calls IAppHostEnvironment.AppDataPath
4. And then the configureLogger Action we can provide manually in the Uno HostBuilder for Serilog is applyed.

So... I guess, if we want to use this extension with having our own templates applyed (no the Serilog Extension provides no access to HostBuilderContext 🫤 so if you want to get your own config in there, I would think, you will need a backing field that is filled with an additional HostBuilder/ConfigurationBuilder before you enter the Uno Hostbuilder...

In my Apps, I prefer to use Serilog especially, when it comes to file logging requirement, which (from my POV) makes always sense as soon as it shall run in Production in any Future 👍