refactor and add some comment.

src/DotNetCore.CAP.Kafka/CAP.KafkaCapOptionsExtension.cs

@@ -5,7 +5,7 @@ using Microsoft.Extensions.DependencyInjection;
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
-    public class KafkaCapOptionsExtension : ICapOptionsExtension
+    internal sealed class KafkaCapOptionsExtension : ICapOptionsExtension
     {
         private readonly Action<KafkaOptions> _configure;
 
@@ -16,10 +16,8 @@ namespace DotNetCore.CAP
 
         public void AddServices(IServiceCollection services)
         {
-            services.Configure(_configure);
-
             var kafkaOptions = new KafkaOptions();
-            _configure(kafkaOptions);
+            _configure?.Invoke(kafkaOptions);
             services.AddSingleton(kafkaOptions);
 
             services.AddSingleton<IConsumerClientFactory, KafkaConsumerClientFactory>();

src/DotNetCore.CAP.Kafka/CAP.Options.Extensions.cs

@@ -6,6 +6,10 @@ namespace Microsoft.Extensions.DependencyInjection
 {
     public static class CapOptionsExtensions
     {
+        /// <summary>
+        /// Configuration to use kafka in CAP.
+        /// </summary>
+        /// <param name="bootstrapServers">Kafka bootstrap server urls.</param>
         public static CapOptions UseKafka(this CapOptions options, string bootstrapServers)
         {
             return options.UseKafka(opt =>
@@ -14,6 +18,11 @@ namespace Microsoft.Extensions.DependencyInjection
             });
         }
 
+        /// <summary>
+        /// Configuration to use kafka in CAP.
+        /// </summary>
+        /// <param name="configure">Provides programmatic configuration for the kafka .</param>
+        /// <returns></returns>
         public static CapOptions UseKafka(this CapOptions options, Action<KafkaOptions> configure)
         {
             if (configure == null) throw new ArgumentNullException(nameof(configure));

src/DotNetCore.CAP.Kafka/CAP.SubscribeAttribute.cs

@@ -3,6 +3,9 @@
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
+    /// <summary>
+    /// An attribute for subscribe Kafka messages.
+    /// </summary>
     public class CapSubscribeAttribute : TopicAttribute
     {
         public CapSubscribeAttribute(string name)

src/DotNetCore.CAP.Kafka/KafkaConsumerClient.cs

@@ -6,7 +6,7 @@ using Confluent.Kafka.Serialization;
 
 namespace DotNetCore.CAP.Kafka
 {
-    public class KafkaConsumerClient : IConsumerClient
+    internal sealed class KafkaConsumerClient : IConsumerClient
     {
         private readonly string _groupId;
         private readonly KafkaOptions _kafkaOptions;

src/DotNetCore.CAP.Kafka/KafkaConsumerClientFactory.cs

@@ -3,13 +3,13 @@ using Microsoft.Extensions.Options;
 
 namespace DotNetCore.CAP.Kafka
 {
-    public class KafkaConsumerClientFactory : IConsumerClientFactory
+    internal sealed class KafkaConsumerClientFactory : IConsumerClientFactory
     {
         private readonly KafkaOptions _kafkaOptions;
 
-        public KafkaConsumerClientFactory(IOptions<KafkaOptions> kafkaOptions)
+        public KafkaConsumerClientFactory(KafkaOptions kafkaOptions)
         {
-            _kafkaOptions = kafkaOptions?.Value ?? throw new ArgumentNullException(nameof(kafkaOptions));
+            _kafkaOptions = kafkaOptions;
         }
 
         public IConsumerClient Create(string groupId)

src/DotNetCore.CAP.Kafka/PublishQueueExecutor.cs

@@ -4,22 +4,21 @@ using System.Threading.Tasks;
 using Confluent.Kafka;
 using DotNetCore.CAP.Processor.States;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Options;
 
 namespace DotNetCore.CAP.Kafka
 {
-    public class PublishQueueExecutor : BasePublishQueueExecutor
+    internal class PublishQueueExecutor : BasePublishQueueExecutor
     {
         private readonly ILogger _logger;
         private readonly KafkaOptions _kafkaOptions;
 
         public PublishQueueExecutor(IStateChanger stateChanger,
-            IOptions<KafkaOptions> options,
+            KafkaOptions options,
             ILogger<PublishQueueExecutor> logger)
             : base(stateChanger, logger)
         {
             _logger = logger;
-            _kafkaOptions = options.Value;
+            _kafkaOptions = options;
         }
 
         public override Task<OperateResult> PublishAsync(string keyName, string content)

src/DotNetCore.CAP.MySql/CAP.MySqlCapOptionsExtension.cs

@@ -7,7 +7,7 @@ using Microsoft.Extensions.DependencyInjection;
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
-    public class MySqlCapOptionsExtension : ICapOptionsExtension
+    internal class MySqlCapOptionsExtension : ICapOptionsExtension
     {
         private readonly Action<MySqlOptions> _configure;
 

src/DotNetCore.CAP.MySql/FetchedMessage.cs

@@ -2,7 +2,7 @@
 
 namespace DotNetCore.CAP.MySql
 {
-    public class FetchedMessage
+    internal class FetchedMessage
     {
         public int MessageId { get; set; }
 

src/DotNetCore.CAP.MySql/IAdditionalProcessor.Default.cs

@@ -7,7 +7,7 @@ using MySql.Data.MySqlClient;
 
 namespace DotNetCore.CAP.MySql
 {
-    public class DefaultAdditionalProcessor : IAdditionalProcessor
+    internal class DefaultAdditionalProcessor : IAdditionalProcessor
     {
         private readonly IServiceProvider _provider;
         private readonly ILogger _logger;

src/DotNetCore.CAP.RabbitMQ/CAP.Options.Extensions.cs

@@ -4,7 +4,7 @@ using DotNetCore.CAP;
 // ReSharper disable once CheckNamespace
 namespace Microsoft.Extensions.DependencyInjection
 {
-    public static class CapOptionsExtensions
+    internal static class CapOptionsExtensions
     {
         public static CapOptions UseRabbitMQ(this CapOptions options, string hostName)
         {

src/DotNetCore.CAP.RabbitMQ/CAP.RabbitMQCapOptionsExtension.cs

@@ -5,7 +5,7 @@ using Microsoft.Extensions.DependencyInjection;
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
-    public class RabbitMQCapOptionsExtension : ICapOptionsExtension
+    internal sealed class RabbitMQCapOptionsExtension : ICapOptionsExtension
     {
         private readonly Action<RabbitMQOptions> _configure;
 
@@ -16,12 +16,9 @@ namespace DotNetCore.CAP
 
         public void AddServices(IServiceCollection services)
         {
-            services.Configure(_configure);
-
-            var rabbitMQOptions = new RabbitMQOptions();
-            _configure(rabbitMQOptions);
-
-            services.AddSingleton(rabbitMQOptions);
+            var options = new RabbitMQOptions();
+            _configure?.Invoke(options);
+            services.AddSingleton(options);
 
             services.AddSingleton<IConsumerClientFactory, RabbitMQConsumerClientFactory>();
             services.AddTransient<IQueueExecutor, PublishQueueExecutor>();

src/DotNetCore.CAP.RabbitMQ/CAP.SubscribeAttribute.cs

@@ -3,6 +3,9 @@
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
+    /// <summary>
+    /// An attribute for subscribe RabbitMQ messages.
+    /// </summary>
     public class CapSubscribeAttribute : TopicAttribute
     {
         public CapSubscribeAttribute(string name) : base(name)

src/DotNetCore.CAP.RabbitMQ/PublishQueueExecutor.cs

@@ -8,18 +8,18 @@ using RabbitMQ.Client;
 
 namespace DotNetCore.CAP.RabbitMQ
 {
-    public class PublishQueueExecutor : BasePublishQueueExecutor
+    internal sealed class PublishQueueExecutor : BasePublishQueueExecutor
     {
         private readonly ILogger _logger;
         private readonly RabbitMQOptions _rabbitMQOptions;
 
         public PublishQueueExecutor(IStateChanger stateChanger,
-            IOptions<RabbitMQOptions> options,
+            RabbitMQOptions options,
             ILogger<PublishQueueExecutor> logger)
             : base(stateChanger, logger)
         {
             _logger = logger;
-            _rabbitMQOptions = options.Value;
+            _rabbitMQOptions = options;
         }
 
         public override Task<OperateResult> PublishAsync(string keyName, string content)

src/DotNetCore.CAP.RabbitMQ/RabbitMQConsumerClient.cs

@@ -7,7 +7,7 @@ using RabbitMQ.Client.Events;
 
 namespace DotNetCore.CAP.RabbitMQ
 {
-    public class RabbitMQConsumerClient : IConsumerClient
+    internal sealed class RabbitMQConsumerClient : IConsumerClient
     {
         private readonly string _exchageName;
         private readonly string _queueName;

src/DotNetCore.CAP.RabbitMQ/RabbitMQConsumerClientFactory.cs

@@ -2,13 +2,13 @@
 
 namespace DotNetCore.CAP.RabbitMQ
 {
-    public class RabbitMQConsumerClientFactory : IConsumerClientFactory
+    internal sealed class RabbitMQConsumerClientFactory : IConsumerClientFactory
     {
         private readonly RabbitMQOptions _rabbitMQOptions;
 
-        public RabbitMQConsumerClientFactory(IOptions<RabbitMQOptions> rabbitMQOptions)
+        public RabbitMQConsumerClientFactory(RabbitMQOptions rabbitMQOptions)
         {
-            _rabbitMQOptions = rabbitMQOptions.Value;
+            _rabbitMQOptions = rabbitMQOptions;
         }
 
         public IConsumerClient Create(string groupId)

src/DotNetCore.CAP.SqlServer/CAP.SqlServerCapOptionsExtension.cs

@@ -7,7 +7,7 @@ using Microsoft.Extensions.DependencyInjection;
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
 {
-    public class SqlServerCapOptionsExtension : ICapOptionsExtension
+    internal class SqlServerCapOptionsExtension : ICapOptionsExtension
     {
         private readonly Action<SqlServerOptions> _configure;
 

src/DotNetCore.CAP.SqlServer/FetchedMessage.cs

@@ -2,7 +2,7 @@
 
 namespace DotNetCore.CAP.SqlServer
 {
-    public class FetchedMessage
+    internal class FetchedMessage
     {
         public int MessageId { get; set; }