Added BaseObjectEqualityComparer.cs for use in LINQ statements.

src/SharpArch/SharpArch.Core/DomainModel/BaseObjectEqualityComparer.cs

@@ -0,0 +1,24 @@
+using System.Collections.Generic;
+
+namespace SharpArch.Core.DomainModel
+{
+    /// <summary>
+    /// Provides a comparer for supporting LINQ methods such as Intersect, Union and Distinct
+    /// </summary>
+    public class BaseObjectEqualityComparer : IEqualityComparer<BaseObject>
+    {
+        public bool Equals(BaseObject firstObject, BaseObject secondObject) {
+            if (firstObject == null && secondObject == null)
+                return true;
+
+            if (firstObject == null ^ secondObject == null)
+                return false;
+
+            return firstObject.Equals(secondObject);
+        }
+
+        public int GetHashCode(BaseObject obj) {
+            return obj.GetHashCode();
+        }
+    }
+}

src/SharpArch/SharpArch.Core/SharpArch.Core.csproj

@@ -56,6 +56,7 @@
     <Compile Include="CommonValidator\IValidator.cs" />
     <Compile Include="DomainModel\BaseObject.cs" />
     <Compile Include="DesignByContract.cs" />
+    <Compile Include="DomainModel\BaseObjectEqualityComparer.cs" />
     <Compile Include="DomainModel\Entity.cs" />
     <Compile Include="DomainModel\IEntityWithTypedId.cs" />
     <Compile Include="DomainModel\IHasAssignedId.cs" />

src/SharpArch/SharpArch.Tests/SharpArch.Core/DomainModel/BaseObjectEqualityComparerTests.cs

@@ -0,0 +1,129 @@
+using NUnit.Framework;
+using SharpArch.Core.DomainModel;
+using System.Reflection;
+using System.Collections.Generic;
+using NUnit.Framework.SyntaxHelpers;
+using SharpArch.Testing;
+
+namespace Tests.SharpArch.Core.DomainModel
+{
+    [TestFixture]
+    public class BaseObjectEqualityComparerTests
+    {
+        [Test]
+        public void CanCompareNulls() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+            Assert.That(comparer.Equals(null, null));
+            Assert.That(comparer.Equals(null, new ConcreteBaseObject()), Is.False);
+            Assert.That(comparer.Equals(new ConcreteBaseObject(), null), Is.False);
+        }
+
+        [Test]
+        public void CannotSuccessfullyCompareDifferentlyTypedObjectsThatDeriveFromBaseObject() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+
+            ConcreteBaseObject object1 = new ConcreteBaseObject() {
+                Name = "Whatever"
+            };
+            ConcreteValueObject object2 = new ConcreteValueObject() {
+                Name = "Whatever"
+            };
+
+            Assert.That(comparer.Equals(object1, object2), Is.False);
+        }
+
+        [Test]
+        public void CanCompareBaseObjects() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+
+            ConcreteBaseObject object1 = new ConcreteBaseObject() {
+                Name = "Whatever"
+            };
+            ConcreteBaseObject object2 = new ConcreteBaseObject() {
+                Name = "Whatever"
+            };
+            Assert.That(comparer.Equals(object1, object2));
+
+            object2.Name = "Mismatch";
+            Assert.That(comparer.Equals(object1, object2), Is.False);
+        }
+
+        [Test]
+        public void CanCompareValueObjects() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+
+            ConcreteValueObject object1 = new ConcreteValueObject() {
+                Name = "Whatever"
+            };
+            ConcreteValueObject object2 = new ConcreteValueObject() {
+                Name = "Whatever"
+            };
+            Assert.That(comparer.Equals(object1, object2));
+
+            object2.Name = "Mismatch";
+            Assert.That(comparer.Equals(object1, object2), Is.False);
+        }
+
+        [Test]
+        public void CanCompareEntitiesWithNoDomainSignatureProperties() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+
+            ConcreteEntityWithNoDomainSignatureProperties object1 = new ConcreteEntityWithNoDomainSignatureProperties() {
+                Name = "Whatever"
+            };
+            ConcreteEntityWithNoDomainSignatureProperties object2 = new ConcreteEntityWithNoDomainSignatureProperties() {
+                Name = "Whatever"
+            };
+            Assert.That(comparer.Equals(object1, object2), Is.False);
+
+            EntityIdSetter.SetIdOf<int>(object1, 1);
+            EntityIdSetter.SetIdOf<int>(object2, 1);
+            Assert.That(comparer.Equals(object1, object2));
+        }
+
+        [Test]
+        public void CanCompareEntitiesWithDomainSignatureProperties() {
+            BaseObjectEqualityComparer comparer = new BaseObjectEqualityComparer();
+
+            ConcreteEntityWithDomainSignatureProperties object1 = new ConcreteEntityWithDomainSignatureProperties() {
+                Name = "Whatever"
+            };
+            ConcreteEntityWithDomainSignatureProperties object2 = new ConcreteEntityWithDomainSignatureProperties() {
+                Name = "Whatever"
+            };
+            Assert.That(comparer.Equals(object1, object2));
+
+            object2.Name = "Mismatch";
+            Assert.That(comparer.Equals(object1, object2), Is.False);
+
+            EntityIdSetter.SetIdOf<int>(object1, 1);
+            EntityIdSetter.SetIdOf<int>(object2, 1);
+            Assert.That(comparer.Equals(object1, object2));
+        }
+
+        private class ConcreteBaseObject : BaseObject
+        {
+            protected override IEnumerable<PropertyInfo> GetTypeSpecificSignatureProperties() {
+                return GetType().GetProperties();
+            }
+
+            public string Name { get; set; }
+        }
+
+        private class ConcreteEntityWithNoDomainSignatureProperties : Entity
+        {
+            public string Name { get; set; }
+        }
+
+        private class ConcreteEntityWithDomainSignatureProperties : Entity
+        {
+            [DomainSignature]
+            public string Name { get; set; }
+        }
+
+        private class ConcreteValueObject : ValueObject
+        {
+            public string Name { get; set; }
+        }
+    }
+}

src/SharpArch/SharpArch.Tests/SharpArch.Tests.csproj

@@ -88,6 +88,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SharpArch.Core.NHibernateValidator\CommonValidatorAdapter\ValidatorTests.cs" />
     <Compile Include="SharpArch.Core\DesignByContractTests.cs" />
+    <Compile Include="SharpArch.Core\DomainModel\BaseObjectEqualityComparerTests.cs" />
     <Compile Include="SharpArch.Core\DomainModel\EntityTests.cs" />
     <Compile Include="SharpArch.Core\DomainModel\ValueObjectTests.cs" />
     <Compile Include="SharpArch.Core\CommonValidator\NHibernateValidator\HasUniqueEntitySignatureValidatorTests.cs" />