Fixing null checks in equality operators (#311)

Author: CoryCharlton

Tests/IPAddressTests/IPAddressTests.cs

@@ -307,18 +307,26 @@ public void Equality_Tests()
         {
             var privateAddress = IPAddress.Parse("192.168.0.1");
             var publicAddress = IPAddress.Parse("1.1.1.1");
+            IPAddress defaultAddress = default;
+            IPAddress nullAddress = null;
+
+            // Is
+            Assert.IsTrue(nullAddress is null, "nullAddress is null");
 
             // Equal
             Assert.AreEqual(privateAddress, IPAddress.Parse("192.168.0.1"));
             Assert.AreEqual(publicAddress, IPAddress.Parse("1.1.1.1"));
             Assert.IsTrue(privateAddress == new IPAddress(new byte[] { 192, 168, 0, 1 }), "192.168.0.1 == 192.168.0.1");
             Assert.IsTrue(publicAddress == new IPAddress(new byte[] { 1, 1, 1, 1 }), "1.1.1.1 == 1.1.1.1");
+            Assert.IsTrue(defaultAddress == default, "default == default");
+            Assert.IsTrue(nullAddress == null, "nullAddress == null");
 
             // Not Equal
             Assert.AreNotEqual(privateAddress, IPAddress.Parse("1.1.1.1"));
             Assert.AreNotEqual(publicAddress, IPAddress.Parse("192.168.0.1"));
             Assert.IsTrue(privateAddress != new IPAddress(new byte[] { 192, 168, 0, 2 }), "192.168.0.1 == 192.168.0.2");
             Assert.IsTrue(publicAddress != new IPAddress(new byte[] { 1, 1, 1, 2 }), "1.1.1.1 == 1.1.1.2");
+            Assert.IsTrue((IPAddress) null != privateAddress, "(IPAddress) null != privateAddress");
         }
     }
 }

nanoFramework.System.Net/IPAddress.cs

@@ -168,7 +168,15 @@ public IPAddress(byte[] address)
         /// <param name="a">The <see cref="IPAddress"/> to compare with <paramref name="b"/>.</param>
         /// <param name="b">The <see cref="IPAddress"/> to compare with <paramref name="a"/>.</param>
         /// <returns><see langword="true"/> if <paramref name="b"/> is equal to <paramref name="a"/>; otherwise, <see langword="false"/>.</returns>   
-        public static bool operator ==(IPAddress a, IPAddress b) => a is not null && a.Equals(b);
+        public static bool operator ==(IPAddress a, IPAddress b)
+        {
+            if (a is null && b is null)
+            {
+                return true;
+            }
+
+            return a is not null && a.Equals(b);
+        }
 
         /// <summary>
         /// Indicates whether two <see cref="IPAddress"/> objects are not equal.