Question

I have written the following method to return a list of Unserializable classes (LINQ classes) from a list of Serializable classes (POCOs):

List<UnSerializableEntity> ToListOfUnserializables(List<SerializableEntity> entityList) {     var tempList = new List<UnSerializableEntity>();     entityList.ForEach(e =>     {         if (e != null)         {             tempList.Add(ConvertFromSerializableToUnserializable(e));          }      });      return tempList; } 

Now, Resharper has ‘complained’ about this line: if (e != null), and suggested to change it to this:

if (!Equals(e, default(SerializableEntity)))  

My question is to what has this change actually improved or prevented from happening? and I know the default keyword in this context has to do something with generics, but I’m not sure what it represents exactly.

PS. UnSerializableEntity and SerializableEntity are class generics.

Answer 1

If SerializableEntity is a value type, it can never be null. Therefore, the body of your if statement will always execute because it is checking for null. The default keyword will return the default value of the generic type. For reference types, the default value is null. For value types, it is zero (or whatever zero represents for that value type).

If you only want reference types as entities, you should set constraints on your generic parameters. For example:

List<UnSerializableEntity> ToListOfUnserializables(List<SerializableEntity> entityList)     where SerializableEntity : class