Exception in Serilog Initialization

Question

I'm attempting to try Serilog out in an asp.net core web api (3.1) but seem to be having trouble with the following:

var configuration = new ConfigurationBuilder()
                    .AddJsonFile("appsettings.log.json", optional: true, reloadOnChange: true)
                    .AddEnvironmentVariables()
                    .Build();

//Configure logger
var loggerConfiguration = new LoggerConfiguration().ReadFrom.Configuration(configuration);

Log.Logger = loggerConfiguration.CreateLogger();   

It is throwing the exception:

Exception has occurred: CLR/System.InvalidOperationException
An unhandled exception of type 'System.InvalidOperationException' occurred in Microsoft.Extensions.Configuration.Binder.dll: 'Cannot create instance of type 'System.String' because it is missing a public parameterless constructor.'
   at Microsoft.Extensions.Configuration.ConfigurationBinder.CreateInstance(Type type)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance(Type type, Object instance, IConfiguration config, BinderOptions options)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.Get(IConfiguration configuration, Type type, Action`1 configureOptions)
   at Microsoft.Extensions.Configuration.ConfigurationBinder.Get(IConfiguration configuration, Type type)
   at Serilog.Settings.Configuration.ObjectArgumentValue.ConvertTo(Type toType, ResolutionContext resolutionContext)
   at Serilog.Settings.Configuration.ConfigurationReader.<>c__DisplayClass18_2.<CallConfigurationMethods>b__3(<>f__AnonymousType9`2 <>h__TransparentIdentifier0)
   at System.Linq.Utilities.<>c__DisplayClass2_0`3.<CombineSelectors>b__0(TSource x)
   at System.Linq.Enumerable.SelectListPartitionIterator`2.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Serilog.Settings.Configuration.ConfigurationReader.CallConfigurationMethods(ILookup`2 methods, IList`1 configurationMethods, Object receiver)
   at Serilog.Settings.Configuration.ConfigurationReader.ApplySinks(LoggerConfiguration loggerConfiguration)
   at Serilog.Settings.Configuration.ConfigurationReader.Configure(LoggerConfiguration loggerConfiguration)
   at Serilog.Configuration.LoggerSettingsConfiguration.Settings(ILoggerSettings settings)
   at Serilog.ConfigurationLoggerConfigurationExtensions.Configuration(LoggerSettingsConfiguration settingConfiguration, IConfiguration configuration, String sectionName, DependencyContext dependencyContext)
   at Serilog.ConfigurationLoggerConfigurationExtensions.Configuration(LoggerSettingsConfiguration settingConfiguration, IConfiguration configuration, DependencyContext dependencyContext)

My appsettings.log.json looks like this:

{
  "Serilog": {
    "Using": [ "Serilog.Sinks.Console" ],
    "MinimumLevel": "Debug",
    "WriteTo": [
      { "Name": "Console" },
      {
        "Name": "File",
        "Args": {
          "path": "%ProgramData%\\Logs\\BoxIt\\BoxIt-{Date}.txt",
          "rollOnFileSizeLimit": "true",
          "rollingInterval": "Day",
          "fileSizeLimitBytes": 10000000,
          "outputTemplate:": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}"
        }
      }
    ],
    "Enrich": [ "FromLogContext", "WithMachineName", "WithThreadId" ],
    "Destructure": [
      {
        "Name": "ToMaximumDepth",
        "Args": { "maximumDestructuringDepth": 4 }
      },
      {
        "Name": "ToMaximumStringLength",
        "Args": { "maximumStringLength": 100 }
      },
      {
        "Name": "ToMaximumCollectionCount",
        "Args": { "maximumCollectionCount": 10 }
      }
    ],
    "Properties": {
      "Application": "Box-It"
    }
  }
}

Most of the articles I've read initialize this in a very similar fashion so I'm not quite sure if there is something wrong with the config file or how I'm reading the configuration.

Answer 1

"outputTemplate:": was the issue here. The colon inside the double quotes was a mistake and was leading to the error above.