Added events to UOW.

src/Volo.Abp/Volo/Abp/Uow/ChildUnitOfWork.cs

@@ -2,11 +2,16 @@ using System;
 using System.Threading;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
+using Volo.ExtensionMethods;
 
 namespace Volo.Abp.Uow
 {
     internal class ChildUnitOfWork : IUnitOfWork
     {
+        public event EventHandler Completed;
+        public event EventHandler<UnitOfWorkFailedEventArgs> Failed;
+        public event EventHandler Disposed;
+
         public IServiceProvider ServiceProvider => _parent.ServiceProvider;
 
         private readonly IUnitOfWork _parent;
@@ -16,6 +21,10 @@ namespace Volo.Abp.Uow
             Check.NotNull(parent, nameof(parent));
 
             _parent = parent;
+
+            _parent.Completed += (sender, args) => { Completed.InvokeSafely(sender, args); };
+            _parent.Failed += (sender, args) => { Failed.InvokeSafely(sender, args); };
+            _parent.Disposed += (sender, args) => { Disposed.InvokeSafely(sender, args); };
         }
 
         public void SaveChanges()
@@ -30,7 +39,7 @@ namespace Volo.Abp.Uow
         
         public void Complete()
         {
-            _parent.Complete();
+            
         }
 
         public Task CompleteAsync(CancellationToken cancellationToken = default(CancellationToken))

src/Volo.Abp/Volo/Abp/Uow/IAmbientUnitOfWork.cs

@@ -1,9 +1,6 @@
-using JetBrains.Annotations;
-
-namespace Volo.Abp.Uow
+namespace Volo.Abp.Uow
 {
     public interface IAmbientUnitOfWork : IUnitOfWorkAccessor
     {
-        void SetUnitOfWork([CanBeNull] IUnitOfWork unitOfWork);
     }
 }

src/Volo.Abp/Volo/Abp/Uow/IBasicUnitOfWork.cs

@@ -7,6 +7,12 @@ namespace Volo.Abp.Uow
     //Find a better naming :(
     public interface IBasicUnitOfWork : IDisposable
     {
+        event EventHandler Completed;
+
+        event EventHandler<UnitOfWorkFailedEventArgs> Failed;
+
+        event EventHandler Disposed;
+
         void SaveChanges();
 
         Task SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken));

src/Volo.Abp/Volo/Abp/Uow/IUnitOfWork.cs

@@ -2,5 +2,6 @@
 {
     public interface IUnitOfWork : IBasicUnitOfWork, IDatabaseApiContainer
     {
+        
     }
 }

src/Volo.Abp/Volo/Abp/Uow/IUnitOfWorkAccessor.cs

@@ -6,5 +6,7 @@ namespace Volo.Abp.Uow
     {
         [CanBeNull]
         IUnitOfWork UnitOfWork { get; }
+
+        void SetUnitOfWork([CanBeNull] IUnitOfWork unitOfWork);
     }
 }

src/Volo.Abp/Volo/Abp/Uow/UnitOfWork.cs

@@ -3,22 +3,27 @@ using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using Volo.DependencyInjection;
+using Volo.ExtensionMethods;
 using Volo.ExtensionMethods.Collections.Generic;
 
 namespace Volo.Abp.Uow
 {
     public class UnitOfWork : IUnitOfWork, ITransientDependency
     {
+        public event EventHandler Completed;
+        public event EventHandler<UnitOfWorkFailedEventArgs> Failed;
+        public event EventHandler Disposed;
+
         public IServiceProvider ServiceProvider { get; }
 
         private readonly Dictionary<string, IDatabaseApi> _databaseApis;
-        private readonly IAmbientUnitOfWork _ambientUnitOfWork;
 
+        private Exception _exception;
+        private bool _isCompleted;
         private bool _isDisposed;
 
-        public UnitOfWork(IServiceProvider serviceProvider, IAmbientUnitOfWork ambientUnitOfWork)
+        public UnitOfWork(IServiceProvider serviceProvider)
         {
-            _ambientUnitOfWork = ambientUnitOfWork;
             ServiceProvider = serviceProvider;
 
             _databaseApis = new Dictionary<string, IDatabaseApi>();
@@ -32,7 +37,13 @@ namespace Volo.Abp.Uow
             }
 
             _isDisposed = true;
-            _ambientUnitOfWork.SetUnitOfWork(null);
+
+            if (!_isCompleted || _exception != null)
+            {
+                OnFailed(_exception);
+            }
+
+            OnDisposed();
         }
 
         public void SaveChanges()
@@ -56,12 +67,33 @@ namespace Volo.Abp.Uow
 
         public void Complete()
         {
-            SaveChanges();
+            PreventMultipleComplete();
+            try
+            {
+                SaveChanges();
+                OnCompleted();
+            }
+            catch (Exception ex)
+            {
+                _exception = ex;
+                throw;
+            }
         }
 
         public async Task CompleteAsync(CancellationToken cancellationToken = default(CancellationToken))
         {
-            await SaveChangesAsync(cancellationToken);
+            PreventMultipleComplete();
+
+            try
+            {
+                await SaveChangesAsync(cancellationToken);
+                OnCompleted();
+            }
+            catch (Exception ex)
+            {
+                _exception = ex;
+                throw;
+            }
         }
 
         public IDatabaseApi FindDatabaseApi(string id)
@@ -76,5 +108,30 @@ namespace Volo.Abp.Uow
 
             return _databaseApis.GetOrAdd(id, factory);
         }
+
+        protected virtual void OnCompleted()
+        {
+            Completed.InvokeSafely(this);
+        }
+
+        protected virtual void OnFailed(Exception exception)
+        {
+            Failed.InvokeSafely(this, new UnitOfWorkFailedEventArgs(exception));
+        }
+
+        protected virtual void OnDisposed()
+        {
+            Disposed.InvokeSafely(this);
+        }
+
+        private void PreventMultipleComplete()
+        {
+            if (_isCompleted)
+            {
+                throw new AbpException("Complete is called before!");
+            }
+
+            _isCompleted = true;
+        }
     }
 }

src/Volo.Abp/Volo/Abp/Uow/UnitOfWorkFailedEventArgs.cs

@@ -0,0 +1,28 @@
+using System;
+using JetBrains.Annotations;
+
+namespace Volo.Abp.Uow
+{
+    /// <summary>
+    /// Used as event arguments on <see cref="IUnitOfWork.Failed"/> event.
+    /// </summary>
+    public class UnitOfWorkFailedEventArgs : EventArgs
+    {
+        /// <summary>
+        /// Exception that caused failure. This is set only if an error occured during <see cref="IBasicUnitOfWork.Complete"/>.
+        /// Can be null if there is no exception, but <see cref="IBasicUnitOfWork.Complete"/> is not called. 
+        /// Can be null if another exception occurred during the UOW.
+        /// </summary>
+        [CanBeNull]
+        public Exception Exception { get; private set; }
+
+        /// <summary>
+        /// Creates a new <see cref="UnitOfWorkFailedEventArgs"/> object.
+        /// </summary>
+        /// <param name="exception">Exception that caused failure</param>
+        public UnitOfWorkFailedEventArgs([CanBeNull] Exception exception)
+        {
+            Exception = exception;
+        }
+    }
+}

src/Volo.Abp/Volo/Abp/Uow/UnitOfWorkManager.cs

@@ -25,10 +25,13 @@ namespace Volo.Abp.Uow
                 return new ChildUnitOfWork(_ambientUnitOfWork.UnitOfWork);
             }
 
+            var parentUow = _ambientUnitOfWork.UnitOfWork;
+
             var scope = _serviceProvider.CreateScope();
+            IUnitOfWork unitOfWork;
             try
             {
-                _ambientUnitOfWork.SetUnitOfWork(scope.ServiceProvider.GetRequiredService<IUnitOfWork>());
+                unitOfWork = scope.ServiceProvider.GetRequiredService<IUnitOfWork>();
             }
             catch
             {
@@ -36,7 +39,28 @@ namespace Volo.Abp.Uow
                 throw;
             }
 
-            Debug.Assert(_ambientUnitOfWork.UnitOfWork != null, "_ambientUnitOfWork.UnitOfWork can not be null since it's set by _ambientUnitOfWork.SetUnitOfWork method!");
+            _ambientUnitOfWork.SetUnitOfWork(unitOfWork);
+
+            Debug.Assert(
+                _ambientUnitOfWork.UnitOfWork != null,
+                "_ambientUnitOfWork.UnitOfWork can not be null since it's set by _ambientUnitOfWork.SetUnitOfWork method!"
+            );
+
+            unitOfWork.Completed += (sender, args) =>
+            {
+                _ambientUnitOfWork.SetUnitOfWork(parentUow);
+            };
+
+            unitOfWork.Failed += (sender, args) =>
+            {
+                _ambientUnitOfWork.SetUnitOfWork(parentUow);
+            };
+
+            unitOfWork.Disposed += (sender, args) =>
+            {
+                scope.Dispose();
+            };
+
             return _ambientUnitOfWork.UnitOfWork;
         }
     }

test/Volo.Abp.Tests/Volo/Abp/Uow/UnitOfWork_Events_Tests.cs

@@ -0,0 +1,113 @@
+using System;
+using Microsoft.Extensions.DependencyInjection;
+using Shouldly;
+using Volo.Abp.Modularity;
+using Volo.Abp.TestBase;
+using Xunit;
+
+namespace Volo.Abp.Uow
+{
+    public class UnitOfWork_Events_Tests : AbpIntegratedTest<IndependentEmptyModule>
+    {
+        private readonly IUnitOfWorkManager _unitOfWorkManager;
+
+        public UnitOfWork_Events_Tests()
+        {
+            _unitOfWorkManager = ServiceProvider.GetRequiredService<IUnitOfWorkManager>();
+        }
+
+        [Fact]
+        public void Should_Trigger_Complete_On_Success()
+        {
+            var completed = false;
+            var disposed = false;
+
+            using (var uow = _unitOfWorkManager.Begin())
+            {
+                uow.Completed += (sender, args) => completed = true;
+                uow.Disposed += (sender, args) => disposed = true;
+
+                uow.Complete();
+
+                completed.ShouldBeTrue();
+            }
+
+            disposed.ShouldBeTrue();
+        }
+
+        [Fact]
+        public void Should_Trigger_Complete_On_Success_In_Child_Uow()
+        {
+            var completed = false;
+            var disposed = false;
+
+            using (var uow = _unitOfWorkManager.Begin())
+            {
+                using (var childUow = _unitOfWorkManager.Begin())
+                {
+                    childUow.Completed += (sender, args) => completed = true;
+                    uow.Disposed += (sender, args) => disposed = true;
+
+                    childUow.Complete();
+
+                    completed.ShouldBeFalse(); //Parent has not been completed yet!
+                    disposed.ShouldBeFalse();
+                }
+
+                completed.ShouldBeFalse(); //Parent has not been completed yet!
+                disposed.ShouldBeFalse();
+
+                uow.Complete();
+
+                completed.ShouldBeTrue(); //It's completed now!
+                disposed.ShouldBeFalse(); //But not disposed yet!
+            }
+
+            disposed.ShouldBeTrue();
+        }
+
+
+        [Fact]
+        public void Should_Not_Trigger_Complete_If_Uow_Is_Not_Completed()
+        {
+            var completed = false;
+            var failed = false;
+            var disposed = false;
+
+            using (var uow = _unitOfWorkManager.Begin())
+            {
+                uow.Completed += (sender, args) => completed = true;
+                uow.Failed += (sender, args) => failed = true;
+                uow.Disposed += (sender, args) => disposed = true;
+            }
+
+            completed.ShouldBeFalse();
+            failed.ShouldBeTrue();
+            disposed.ShouldBeTrue();
+        }
+
+        [Fact]
+        public void Should_Trigger_Failed_If_Uow_Throws_Exception()
+        {
+            var completed = false;
+            var failed = false;
+            var disposed = false;
+
+            Assert.Throws<Exception>(new Action(() =>
+            {
+                using (var uow = _unitOfWorkManager.Begin())
+                {
+                    uow.Completed += (sender, args) => completed = true;
+                    uow.Failed += (sender, args) => failed = true;
+                    uow.Disposed += (sender, args) => disposed = true;
+
+                    throw new Exception("test exception");
+                }
+            })).Message.ShouldBe("test exception");
+
+            completed.ShouldBeFalse();
+            failed.ShouldBeTrue();
+            disposed.ShouldBeTrue();
+        }
+    }
+}