Standardized implementation of IEquatable, !=, ==, Equals and GetHashCode for MongoGridFSFileInfo.

Author: rstam

Driver/GridFS/MongoGridFSFileInfo.cs

@@ -233,25 +233,38 @@ public DateTime UploadDate
 
         // public operators
         /// <summary>
-        /// Compares two MongoGridFSFileInfos.
+        /// Determines whether two specified MongoGridFSFileInfo objects have different values.
         /// </summary>
-        /// <param name="lhs">The first MongoGridFSFileInfo.</param>
-        /// <param name="rhs">The other MongoGridFSFileInfo.</param>
-        /// <returns>True if the two MongoGridFSFileInfos are not equal (or one is null and the other is not).</returns>
+        /// <param name="lhs">The first value to compare, or null.</param>
+        /// <param name="rhs">The second value to compare, or null.</param>
+        /// <returns>True if the value of lhs is different from the value of rhs; otherwise, false.</returns>
         public static bool operator !=(MongoGridFSFileInfo lhs, MongoGridFSFileInfo rhs)
         {
-            return !(lhs == rhs);
+            return !MongoGridFSFileInfo.Equals(lhs, rhs);
         }
 
         /// <summary>
-        /// Compares two MongoGridFSFileInfos.
+        /// Determines whether two specified MongoGridFSFileInfo objects have the same value.
         /// </summary>
-        /// <param name="lhs">The first MongoGridFSFileInfo.</param>
-        /// <param name="rhs">The other MongoGridFSFileInfo.</param>
-        /// <returns>True if the two MongoGridFSFileInfos are equal (or both null).</returns>
+        /// <param name="lhs">The first value to compare, or null.</param>
+        /// <param name="rhs">The second value to compare, or null.</param>
+        /// <returns>True if the value of lhs is the same as the value of rhs; otherwise, false.</returns>
         public static bool operator ==(MongoGridFSFileInfo lhs, MongoGridFSFileInfo rhs)
         {
-            return object.Equals(lhs, rhs);
+            return MongoGridFSFileInfo.Equals(lhs, rhs);
+        }
+
+        // public static methods
+        /// <summary>
+        /// Determines whether two specified MongoGridFSFileInfo objects have the same value.
+        /// </summary>
+        /// <param name="lhs">The first value to compare, or null.</param>
+        /// <param name="rhs">The second value to compare, or null.</param>
+        /// <returns>True if the value of lhs is the same as the value of rhs; otherwise, false.</returns>
+        public static bool Equals(MongoGridFSFileInfo lhs, MongoGridFSFileInfo rhs)
+        {
+            if ((object)lhs == null) { return (object)rhs == null; }
+            return lhs.Equals(rhs);
         }
 
         // public methods
@@ -334,13 +347,14 @@ public void Delete()
         }
 
         /// <summary>
-        /// Compares this MongoGridFSFileInfo to another MongoGridFSFileInfo.
+        /// Determines whether this instance and another specified MongoGridFSFileInfo object have the same value.
         /// </summary>
-        /// <param name="rhs">The other MongoGridFSFileInfo.</param>
-        /// <returns>True if the two MongoGridFSFileInfos are equal.</returns>
+        /// <param name="rhs">The MongoGridFSFileInfo object to compare to this instance.</param>
+        /// <returns>True if the value of the rhs parameter is the same as this instance; otherwise, false.</returns>
         public bool Equals(MongoGridFSFileInfo rhs)
         {
-            if (object.ReferenceEquals(rhs, null) || GetType() != rhs.GetType()) { return false; }
+            if ((object)rhs == null || GetType() != rhs.GetType()) { return false; }
+            if ((object)this == (object)rhs) { return true; }
             return
                 (_aliases == null && rhs._aliases == null || _aliases != null && rhs._aliases != null && _aliases.SequenceEqual(rhs._aliases)) &&
                 _chunkSize == rhs._chunkSize &&
@@ -354,19 +368,19 @@ public bool Equals(MongoGridFSFileInfo rhs)
         }
 
         /// <summary>
-        /// Compares this MongoGridFSFileInfo to another object.
+        /// Determines whether this instance and a specified object, which must also be a MongoGridFSFileInfo object, have the same value.
         /// </summary>
-        /// <param name="obj">The other object.</param>
-        /// <returns>True if the other object is a MongoGridFSFileInfo and equal to this one.</returns>
+        /// <param name="obj">The MongoGridFSFileInfo object to compare to this instance.</param>
+        /// <returns>True if obj is a MongoGridFSFileInfo object and its value is the same as this instance; otherwise, false.</returns>
         public override bool Equals(object obj)
         {
             return Equals(obj as MongoGridFSFileInfo); // works even if obj is null or of a different type
         }
 
         /// <summary>
-        /// Gets the hash code.
+        /// Returns the hash code for this MongoGridFSFileInfo object.
         /// </summary>
-        /// <returns>The hash code.</returns>
+        /// <returns>A 32-bit signed integer hash code.</returns>
         public override int GetHashCode()
         {
             // see Effective Java by Joshua Bloch

DriverUnitTests/GridFS/MongoGridFSFileInfoTests.cs

@@ -72,29 +72,34 @@ public void TestCreateWithRemoteFileNameAndCreateOptions()
         public void TestEquals()
         {
             var createOptions = new MongoGridFSCreateOptions { ChunkSize = 123 };
-            var a = new MongoGridFSFileInfo(_gridFS, "f", createOptions);
-            var b = new MongoGridFSFileInfo(_gridFS, "f", createOptions);
-            var c = new MongoGridFSFileInfo(_gridFS, "g", createOptions);
-            var n = (MongoCredentials)null;
+            var a1 = new MongoGridFSFileInfo(_gridFS, "f", createOptions);
+            var a2 = new MongoGridFSFileInfo(_gridFS, "f", createOptions);
+            var a3 = a2;
+            var b = new MongoGridFSFileInfo(_gridFS, "g", createOptions);
+            var null1 = (MongoGridFSFileInfo)null;
+            var null2 = (MongoGridFSFileInfo)null;
 
-            Assert.IsTrue(object.Equals(a, b));
-            Assert.IsFalse(object.Equals(a, c));
-            Assert.IsFalse(a.Equals(n));
-            Assert.IsFalse(a.Equals(null));
+            Assert.AreNotSame(a1, a2);
+            Assert.AreSame(a2, a3);
+            Assert.IsTrue(a1.Equals((object)a2));
+            Assert.IsFalse(a1.Equals((object)null));
+            Assert.IsFalse(a1.Equals((object)"x"));
 
-            Assert.IsTrue(a == b);
-            Assert.IsFalse(a == c);
-            Assert.IsFalse(a == null);
-            Assert.IsFalse(null == a);
-            Assert.IsTrue(n == null);
-            Assert.IsTrue(null == n);
+            Assert.IsTrue(a1 == a2);
+            Assert.IsTrue(a2 == a3);
+            Assert.IsFalse(a1 == b);
+            Assert.IsFalse(a1 == null1);
+            Assert.IsFalse(null1 == a1);
+            Assert.IsTrue(null1 == null2);
 
-            Assert.IsFalse(a != b);
-            Assert.IsTrue(a != c);
-            Assert.IsTrue(a != null);
-            Assert.IsTrue(null != a);
-            Assert.IsFalse(n != null);
-            Assert.IsFalse(null != n);
+            Assert.IsFalse(a1 != a2);
+            Assert.IsFalse(a2 != a3);
+            Assert.IsTrue(a1 != b);
+            Assert.IsTrue(a1 != null1);
+            Assert.IsTrue(null1 != a1);
+            Assert.IsFalse(null1 != null2);
+
+            Assert.AreEqual(a1.GetHashCode(), a2.GetHashCode());
         }
     }
 }