Do not add duplicate assemblies.

framework/src/Volo.Abp.Core/Volo/Abp/AbpApplicationBase.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 using JetBrains.Annotations;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
@@ -136,6 +137,8 @@ namespace Volo.Abp
                 }
             }
 
+            var assemblies = new HashSet<Assembly>();
+
             //ConfigureServices
             foreach (var module in Modules)
             {
@@ -143,7 +146,12 @@ namespace Volo.Abp
                 {
                     if (!abpModule.SkipAutoServiceRegistration)
                     {
-                        Services.AddAssembly(module.Type.Assembly);
+                        var assembly = module.Type.Assembly;
+                        if (!assemblies.Contains(assembly))
+                        {
+                            Services.AddAssembly(assembly);
+                            assemblies.Add(assembly);
+                        }
                     }
                 }
 

framework/test/Volo.Abp.Core.Tests/Volo/Abp/DependencyInjection/AutoServiceRegistration_Tests.cs

@@ -0,0 +1,41 @@
+using System.Linq;
+using Microsoft.Extensions.DependencyInjection;
+using Shouldly;
+using Volo.Abp.Modularity;
+using Xunit;
+
+namespace Volo.Abp.DependencyInjection
+{
+    public class AutoServiceRegistration_Tests
+    {
+        [Fact]
+        public void AutoServiceRegistration_Should_Not_Duplicate_Test()
+        {
+            using (var application = AbpApplicationFactory.Create<TestModule>())
+            {
+                //Act
+                application.Initialize();
+
+                //Assert
+                var services = application.ServiceProvider.GetServices<TestService>().ToList();
+                services.Count.ShouldBe(1);
+            }
+        }
+    }
+
+    [DependsOn(typeof(TestDependedModule))]
+    public class TestModule : AbpModule
+    {
+
+    }
+
+    public class TestDependedModule : AbpModule
+    {
+
+    }
+
+    public class TestService : ITransientDependency
+    {
+
+    }
+}