Error when using case-sensitive configuration providers

[KuJIT1]

LoggingConfigurationElement.VariablesKey constant value = "Variables". This means that the correct configuration for the variable section should look like this:

{ 
  "NLog": { 
    "Variables": { 
      "DefaultMinLevel": "Debug", 
      "DefaultTargetNames": "logfile" 
  }
}

What does not match the json schema https://www.schemastore.org/appsettings.json

This does not affect work in normal cases, because the default configuration providers are case-insensitive, but for case-sensitive providers it is misleading.

[KuJIT1]

The following exception is thrown if you use the "variables" key with a lowercase letter when using a case-sensitive configuration provider:

Unhandled exception. NLog.NLogConfigurationException: Property 'value' has blank value, for element 'Variable' in section 'variables'
   at NLog.Config.LoggingConfigurationParser.AssertNonEmptyValue(String value, String propertyName, String elementName, String sectionName)
   at NLog.Config.LoggingConfigurationParser.AssertNotNullValue(Object value, String propertyName, String elementName, String sectionName)
   at NLog.Config.LoggingConfigurationParser.ParseVariableElement(ValidatedConfigurationElement variableElement)
   at NLog.Config.LoggingConfigurationParser.ParseNLogSection(ILoggingConfigurationElement configSection)
   at NLog.Config.LoggingConfigurationParser.LoadConfig(ILoggingConfigurationElement nlogConfig, String basePath)
   at NLog.Extensions.Logging.NLogLoggingConfiguration.LoadConfigurationSection(IConfigurationSection nlogConfig)
   at NLog.Extensions.Logging.NLogLoggingConfiguration..ctor(IConfigurationSection nlogConfig, LogFactory logFactory)
   at NLog.Extensions.Logging.RegisterNLogLoggingProvider.<>c__DisplayClass1_0.<TryLoadConfigurationFromSection>b__0(ISetupLoadConfigurationBuilder configBuilder)
   at NLog.SetupBuilderExtensions.LoadConfiguration(ISetupBuilder setupBuilder, Action`1 configBuilder)
   at NLog.Extensions.Logging.RegisterNLogLoggingProvider.TryLoadConfigurationFromSection(NLogLoggerProvider loggerProvider, IConfiguration configuration)
   at NLog.Extensions.Logging.RegisterNLogLoggingProvider.CreateNLogLoggerProvider(IServiceProvider serviceProvider, IConfiguration hostConfiguration, NLogProviderOptions options, LogFactory logFactory)
   at NLog.Extensions.Logging.ConfigureExtensions.CreateNLogLoggerProvider(IServiceProvider serviceProvider, IConfiguration hostConfiguration, NLogProviderOptions options, LogFactory logFactory)
   at NLog.Extensions.Logging.ConfigureExtensions.CreateNLogLoggerProvider(IServiceProvider serviceProvider, IConfiguration hostConfiguration, NLogProviderOptions options)
   at NLog.Extensions.Logging.RegisterNLogLoggingProvider.<>c__DisplayClass0_0.<TryAddNLogLoggingProvider>b__0(IServiceProvider serviceProvider)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitIEnumerable(IEnumerableCallSite enumerableCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(ServiceIdentifier serviceIdentifier)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier serviceIdentifier, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.Extensions.Hosting.HostBuilder.<>c__DisplayClass35_0.<PopulateServiceCollection>b__2(IServiceProvider _)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(ServiceIdentifier serviceIdentifier)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier serviceIdentifier, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.Extensions.Hosting.HostBuilder.ResolveHost(IServiceProvider serviceProvider, DiagnosticListener diagnosticListener)
   at Microsoft.Extensions.Hosting.HostBuilder.Build()

[snakefoot]

Think you need to provide the appsetting.json that is failing for you. I have just tried this (with lowercase variables) without any issues:

{
    "Logging": {
        "NLog": {
            "IncludeScopes": false,
        }
    },
    "NLog": {
        "internalLogLevel": "Info",
        "internalLogToConsole": true,
        "throwConfigExceptions": true,
        "variables": {
          "defaultlayout": "${date}|${level:uppercase=true}|${message} ${exception:format=tostring}|${logger}|${all-event-properties}"
        },
        "targets": {
            "console": {
                "type": "Console",
                "layout": "${defaultlayout}"
            }
        },
        "rules": [
            {
                "logger": "*",
                "minLevel": "Trace",
                "writeTo": "Console"
            }
        ]
    }
}

[KuJIT1]

If this config was read from a json file by a standard provider, then this is how it should be. We were talking about configuration providers that are case sensitive

[snakefoot]

The Microsoft Json-File-Parser has case-insensitive section-lookups, so it seems to be the standard. Pull-requests are ofcourse welcome if you see places that can be improved (along with unit-tests)