String comparison in .NET strange behavior !

Question

Someone can explain me why this test fails :

        [TestMethod]
     public void WierdComparison()
     {
      var machineConf = ConfigurationManager.OpenMachineConfiguration();
      var systemWeb = machineConf.GetSectionGroup("system.web") as SystemWebSectionGroup;
      var prov = systemWeb.Membership.Providers.OfType<ProviderSettings>().Where((s) => s.Name == "AspNetSqlMembershipProvider").First();

      bool result, expected;
      var connectionStringName = prov.ElementInformation.Properties["connectionStringName"].Value;


      result = connectionStringName.Equals("LocalSqlServer");
      expected = true;

      Assert.AreEqual(expected, result);

      result = connectionStringName == "LocalSqlServer";
      expected = true;

      Assert.AreEqual(expected, result); //This assertion fails
     }

Answer 1

That is because you are comparing an Object to a String.

If you compare two strings, the == operator is overloaded to compare the values of the strings. If you compare an object and a string, the == operator that compares two Object references is used, and that simply compares the references, not the values.

The Equals method is a virtual method, so eventhough you call it on an Object reference, it will still use the overridden method in the String class as the actual type of the object is String.