Null or default comparison of generic argument in C#

To avoid boxing, the best way to compare generics for equality is with EqualityComparer<T>.Default. This respects IEquatable<T> (without boxing) as well as object.Equals, and handles all the Nullable<T> “lifted” nuances. Hence:

if(EqualityComparer<T>.Default.Equals(obj, default(T))) {
    return obj;
}

This will match:

• null for classes
• null (empty) for Nullable<T>
• zero/false/etc for other structs