Introduce AddNLog with NLog-config parameter

src/NLog.Extensions.Hosting/Extensions/ConfigureExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Reflection;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
@@ -36,30 +37,28 @@ public static IHostBuilder UseNLog(this IHostBuilder builder)
         public static IHostBuilder UseNLog(this IHostBuilder builder, NLogProviderOptions options)
         {
             if (builder == null) throw new ArgumentNullException(nameof(builder));
+            builder.ConfigureServices((builderContext, services) => AddNLogLoggerProvider(services, builderContext.Configuration, options, CreateNLogLoggerProvider));
+            return builder;
+        }
 
-            builder.ConfigureServices((hostbuilder, services) =>
-            {
-                ConfigurationItemFactory.Default.RegisterItemsFromAssembly(typeof(ConfigureExtensions).GetTypeInfo()
-                    .Assembly);
-
-                if (hostbuilder.Configuration != null)
-                    ConfigSettingLayoutRenderer.DefaultConfiguration = hostbuilder.Configuration;
+        private static void AddNLogLoggerProvider(IServiceCollection services, IConfiguration configuration, NLogProviderOptions options, Func<IServiceProvider, IConfiguration, NLogProviderOptions, NLogLoggerProvider> factory)
+        {
+            ConfigurationItemFactory.Default.RegisterItemsFromAssembly(typeof(ConfigureExtensions).GetTypeInfo().Assembly);
+            services.Replace(ServiceDescriptor.Singleton<ILoggerProvider, NLogLoggerProvider>(serviceProvider => factory(serviceProvider, configuration, options)));
+        }
 
-                // Try adding Singleton-implementation if not already exists
-                services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, NLogLoggerProvider>(serviceProvider =>
+        private static NLogLoggerProvider CreateNLogLoggerProvider(IServiceProvider serviceProvider, IConfiguration configuration, NLogProviderOptions options)
+        {
+            NLogLoggerProvider provider = new NLogLoggerProvider(options);
+            if (configuration != null)
+            {
+                ConfigSettingLayoutRenderer.DefaultConfiguration = configuration;
+                if (options == null)
                 {
-                    var provider = new NLogLoggerProvider(options ?? new NLogProviderOptions());
-                    if (hostbuilder.Configuration != null)
-                    {
-                        ConfigSettingLayoutRenderer.DefaultConfiguration = hostbuilder.Configuration;
-                        if (options == null)
-                            provider.Configure(hostbuilder.Configuration.GetSection("Logging:NLog"));
-                    }
-                    return provider;
-                }));
-            });
-
-            return builder;
+                    provider.Configure(configuration.GetSection("Logging:NLog"));
+                }
+            }
+            return provider;
         }
     }
 }

src/NLog.Extensions.Logging/Extensions/ConfigureExtensions.cs

@@ -56,7 +56,7 @@ public static ILoggerFactory AddNLog(this ILoggerFactory factory, NLogProviderOp
 #endif
         public static ILoggerFactory AddNLog(this ILoggerFactory factory, IConfiguration configuration)
         {
-            var provider = CreateNLogProvider(configuration);
+            var provider = CreateNLogLoggerProvider(null, configuration, null);
             factory.AddProvider(provider);
             return factory;
         }
@@ -69,7 +69,7 @@ public static ILoggerFactory AddNLog(this ILoggerFactory factory, IConfiguration
         /// <returns>ILoggerFactory for chaining</returns>
         public static ILoggingBuilder AddNLog(this ILoggingBuilder factory)
         {
-            return factory.AddNLog(NLogProviderOptions.Default);
+            return factory.AddNLog((NLogProviderOptions)null);
         }
 
         /// <summary>
@@ -80,8 +80,7 @@ public static ILoggingBuilder AddNLog(this ILoggingBuilder factory)
         /// <returns>ILoggerFactory for chaining</returns>
         public static ILoggingBuilder AddNLog(this ILoggingBuilder factory, IConfiguration configuration)
         {
-            // Try adding Singleton-implementation if not already exists
-            factory.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, NLogLoggerProvider>(s => CreateNLogProvider(configuration)));
+            AddNLogLoggerProvider(factory.Services, configuration, null, CreateNLogLoggerProvider);
             return factory;
         }
 
@@ -93,10 +92,50 @@ public static ILoggingBuilder AddNLog(this ILoggingBuilder factory, IConfigurati
         /// <returns>ILoggerFactory for chaining</returns>
         public static ILoggingBuilder AddNLog(this ILoggingBuilder factory, NLogProviderOptions options)
         {
-            // Try adding Singleton-implementation if not already exists
-            factory.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, NLogLoggerProvider>(s => new NLogLoggerProvider(options)));
+            AddNLogLoggerProvider(factory.Services, null, options, CreateNLogLoggerProvider);
             return factory;
         }
+
+        /// <summary>
+        /// Enable NLog as logging provider for Microsoft Extension Logging
+        /// </summary>
+        /// <param name="builder"></param>
+        /// <param name="configuration">New NLog config.</param>
+        /// <returns></returns>
+        public static ILoggingBuilder AddNLog(this ILoggingBuilder builder, LoggingConfiguration configuration)
+        {
+            AddNLogLoggerProvider(builder.Services, null, null, (serviceProvider, config, options) =>
+            {
+                var provider = CreateNLogLoggerProvider(serviceProvider, config, options);
+                // Delay initialization of targets until we have loaded config-settings
+                LogManager.Configuration = configuration;
+                return provider;
+            });
+            return builder;
+        }
+
+        /// <summary>
+        /// Enable NLog as logging provider for Microsoft Extension Logging
+        /// </summary>
+        /// <param name="builder"></param>
+        /// <param name="configFileRelativePath">relative path to NLog configuration file.</param>
+        /// <returns></returns>
+        public static ILoggingBuilder AddNLog(this ILoggingBuilder builder, string configFileRelativePath)
+        {
+            AddNLogLoggerProvider(builder.Services, null, null, (serviceProvider, config, options) =>
+            {
+                var provider = CreateNLogLoggerProvider(serviceProvider, config, options);
+                // Delay initialization of targets until we have loaded config-settings
+                LogManager.LoadConfiguration(configFileRelativePath);
+                return provider;
+            });
+            return builder;
+        }
+
+        private static void AddNLogLoggerProvider(IServiceCollection services, IConfiguration configuration, NLogProviderOptions options, Func<IServiceProvider, IConfiguration, NLogProviderOptions, NLogLoggerProvider> factory)
+        {
+            services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, NLogLoggerProvider>(serviceProvider => factory(serviceProvider, configuration, options)));
+        }
 #endif
 
         /// <summary>
@@ -157,15 +196,18 @@ public static NLogLoggerProvider Configure(this NLogLoggerProvider nlogProvider,
             return nlogProvider;
         }
 
-        private static NLogLoggerProvider CreateNLogProvider(IConfiguration configuration)
+        private static NLogLoggerProvider CreateNLogLoggerProvider(IServiceProvider serviceProvider, IConfiguration configuration, NLogProviderOptions options)
         {
-            var provider = new NLogLoggerProvider(new NLogProviderOptions());
+            NLogLoggerProvider provider = new NLogLoggerProvider(options ?? NLogProviderOptions.Default);
+            configuration = configuration ?? (serviceProvider?.GetService(typeof(IConfiguration)) as IConfiguration);
             if (configuration != null)
             {
                 ConfigSettingLayoutRenderer.DefaultConfiguration = configuration;
-                provider.Configure(configuration.GetSection("Logging:NLog"));
+                if (options == null)
+                {
+                    provider.Configure(configuration.GetSection("Logging:NLog"));
+                }
             }
-
             return provider;
         }
     }

test/NLog.Extensions.Logging.Tests/Extensions/ConfigureExtensionsTests.cs

@@ -60,8 +60,7 @@ public void AddNLog_LogginBuilder_LogInfo_ShouldLogToNLog()
             var config = CreateConfigWithMemoryTarget(out var memoryTarget);
 
             // Act
-            builder.AddNLog();
-            LogManager.Configuration = config;
+            builder.AddNLog(config);
             var provider = GetLoggerProvider(builder);
             var logger = provider.CreateLogger("logger1");
 
@@ -84,7 +83,7 @@ internal class LoggingBuilderStub : ILoggingBuilder
             public IServiceCollection Services { get; set; } = new ServiceCollection();
         }
 #endif
-        
+
         private static void AssertSingleMessage(MemoryTarget memoryTarget, string expectedMessage)
         {
             Assert.Equal(1, memoryTarget.Logs.Count);