Add HasValue and IsEmpty properties

ValueOf.Tests/HasValue.cs

@@ -0,0 +1,72 @@
+using System;
+using NUnit.Framework;
+
+namespace ValueOf.Tests
+{
+    public class IntId : ValueOf<int, IntId> { }
+    public class StringId : ValueOf<string, StringId> { }
+    public class GuidId : ValueOf<Guid, GuidId> { }
+
+    public class HasValue
+    {
+        [Test]
+        public void HasValueWhenDefaultIntegerIdThenHasValueIsFalseAndIsEmptyIsTrue()
+        {
+            var id = new IntId();
+
+            Assert.IsFalse(id.HasValue);
+            Assert.IsTrue(id.IsEmpty);
+        }
+
+        [Test]
+        public void HasValueWhenEmptyStringIdThenHasValueIsFalseAndIsEmptyIsTrue()
+        {
+            var id = new StringId();
+
+            Assert.IsFalse(id.HasValue);
+            Assert.IsTrue(id.IsEmpty);
+        }
+
+        [Test]
+        public void HasValueWhenDefaultGuidIdThenHasValueIsFalseAndIsEmptyIsTrue()
+        {
+            var id = new GuidId();
+
+            Assert.IsFalse(id.HasValue);
+            Assert.IsTrue(id.IsEmpty);
+        }
+
+        [Test]
+        public void HasValueWhenIntegerIdThenHasValueIsTrueAndIsEmptyIsFalse()
+        {
+            var value = new Random().Next(1, 100);
+            var id = IntId.From(value);
+
+            Assert.IsTrue(id.HasValue);
+            Assert.IsFalse(id.IsEmpty);
+            Assert.AreEqual(value, id.Value);
+        }
+
+        [Test]
+        public void HasValueWhenStringIdThenHasValueIsTrueAndIsEmptyIsFalse()
+        {
+            var value = Guid.NewGuid().ToString();
+            var id = StringId.From(value);
+
+            Assert.IsTrue(id.HasValue);
+            Assert.IsFalse(id.IsEmpty);
+            Assert.AreEqual(value, id.Value);
+        }
+
+        [Test]
+        public void HasValueWhenGuidIdThenHasValueIsTrueAndIsEmptyIsFalse()
+        {
+            var value = Guid.NewGuid();
+            var id = GuidId.From(value);
+
+            Assert.IsTrue(id.HasValue);
+            Assert.IsFalse(id.IsEmpty);
+            Assert.AreEqual(value, id.Value);
+        }
+    }
+}

ValueOf.Tests/ValueOf.Tests.csproj

@@ -5,9 +5,9 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="nunit" Version="3.13.2" />
-    <PackageReference Include="NUnit.Console" Version="3.14.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+    <PackageReference Include="nunit" Version="3.13.3" />
+    <PackageReference Include="NUnit.Console" Version="3.16.3" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.4.2" />
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
   </ItemGroup>
 

ValueOf/ValueOf.cs

@@ -41,6 +41,10 @@ static ValueOf()
 
         public TValue Value { get; protected set; }
 
+        public bool HasValue => Value != null && !Value.Equals(default(TValue));
+
+        public bool IsEmpty => !HasValue;
+
         public static TThis From(TValue item)
         {
             TThis x = Factory();