Serilog ExpressionTemplate rename log level and apply formatting

Question

I'm trying to use serilog's ExpressionTemplate and write the log level in the following way:

{ "level": "INF", ... }

I know how to alias @l to level - level: @l and I know how to format the level to three upper-case letters - @l:u3 but I'm unable to combine the two

I have tried the following without success (fails when trying to format the template with an exception):

level: @l:u3

{'level': @l:u3}

Answer 1

At the time of writing this is a limitation in Serilog.Expressions, which will hopefully be addressed soon.

Update: version 3.4.0-dev-* now on NuGet supports ToString(@l, 'u3').

You can work around it with conditionals:

{'level': if @l = 'Information' then 'INF' else if @l = 'Warning' then 'WRN' else 'ERR'}

With a few more branches for remaining levels.

(Alternatively, you could write and plug in a user defined function along the lines of ToShortLevel(@l), and use that instead.)