Don't allow set endtime before starttime.

eventhub/src/EventHub.Domain.Shared/EventHubErrorCodes.cs

@@ -4,5 +4,6 @@
     {
         public const string OrganizationNameAlreadyExists = "EventHub:OrganizationNameAlreadyExists";
         public const string NotAuthorizedToCreateEventInThisOrganization = "EventHub:NotAuthorizedToCreateEventInThisOrganization";
+        public const string EventEndTimeCantBeEarlierThanStartTime = "EventHub:EventEndTimeCantBeEarlierThanStartTime";
     }
 }

eventhub/src/EventHub.Domain.Shared/Localization/EventHub/en.json

@@ -18,6 +18,7 @@
     "DisplayName:Capacity": "Capacity",
     "EventHub:OrganizationNameAlreadyExists": "The organization {Name} already exists. Please use another name.",
     "EventHub:NotAuthorizedToCreateEventInThisOrganization": "You are not authorized to create events for the organization {OrganizationName}",
+    "EventHub:EventEndTimeCantBeEarlierThanStartTime": "Event end time can not be earlier than the start time.",
     "Events": "Events",
     "Members": "Members",
     "SeeOrganization": "See Organization",

eventhub/src/EventHub.Domain/Events/Event.cs

@@ -25,7 +25,7 @@ namespace EventHub.Events
 
         }
 
-        public Event(
+        internal Event(
             Guid id,
             Guid organizationId,
             string title,
@@ -54,6 +54,11 @@ namespace EventHub.Events
 
         public Event SetTime(DateTime startTime, DateTime endTime)
         {
+            if (startTime > endTime)
+            {
+                throw new BusinessException(EventHubErrorCodes.EventEndTimeCantBeEarlierThanStartTime);
+            }
+
             StartTime = startTime;
             EndTime = endTime;
             return this;

eventhub/src/EventHub.Domain/Events/EventManager.cs

@@ -7,20 +7,22 @@ namespace EventHub.Events
 {
     public class EventManager : DomainService
     {
-        public async Task<Event> CreateAsync(
+        public ValueTask<Event> CreateAsync(
             Organization organization,
             string title,
             DateTime startTime,
             DateTime endTime,
             string description)
         {
-            return new Event(
-                GuidGenerator.Create(),
-                organization.Id,
-                title,
-                startTime,
-                endTime,
-                description
+            return ValueTask.FromResult(
+                new Event(
+                    GuidGenerator.Create(),
+                    organization.Id,
+                    title,
+                    startTime,
+                    endTime,
+                    description
+                )
             );
         }
     }

eventhub/test/EventHub.Domain.Tests/Events/EventTests.cs

@@ -0,0 +1,28 @@
+using System;
+using Shouldly;
+using Volo.Abp;
+using Xunit;
+
+namespace EventHub.Events
+{
+    public class EventTests
+    {
+        [Fact]
+        public void Should_Not_Allow_End_Time_To_Be_Earlier_Than_Start_Time()
+        {
+            var exception = Assert.Throws<BusinessException>(() =>
+            {
+                new Event(
+                    Guid.NewGuid(),
+                    Guid.NewGuid(),
+                    "Introduction to the ABP Framework",
+                    DateTime.Now,
+                    DateTime.Now.AddDays(-2),
+                    "In this event, we will introduce the ABP Framework and explore the fundamental features."
+                );
+            });
+
+            exception.Code.ShouldBe(EventHubErrorCodes.EventEndTimeCantBeEarlierThanStartTime);
+        }
+    }
+}