Inheritance

Use DeepCopyExtension to create copies of instances within class hierarchy.

Example

Your code:

[DeepCopyExtension]
public static BaseClass DeepCopy(this BaseClass baseClass) => baseClass;

public class BaseClass { ... }
public class DerivedClass : BaseClass { ... }
public class OtherDerivedClass : BaseClass { ... }

What gets compiled:

public static BaseClass DeepCopy(this BaseClass baseClass) {
    if (baseClass == null)
        return (BaseClass) null;
    if (baseClass is DerivedClass derivedClass)
        return (BaseClass) new DerivedClass(derivedClass);
    if (baseClass is OtherDerivedClass otherDerivedClass)
        return (BaseClass) new OtherDerivedClass(otherDerivedClass);
    return new BaseClass(baseClass);
}

Example for abstract base class

Your code:

[DeepCopyExtension]
public static AbstractBaseClass DeepCopy(this AbstractBaseClass baseClass) => baseClass;

public class AbstractBaseClass { ... }
public class DerivedClass : AbstractBaseClass { ... }
public class OtherDerivedClass : AbstractBaseClass { ... }

What gets compiled:

public static AbstractBaseClass DeepCopy(this AbstractBaseClass baseClass) {
    if (baseClass == null)
        return (AbstractBaseClass) null;
    if (baseClass is DerivedClass derivedClass)
        return (AbstractBaseClass) new DerivedClass(derivedClass);
    if (baseClass is OtherDerivedClass otherDerivedClass)
        return (AbstractBaseClass) new OtherDerivedClass(otherDerivedClass);
    throw new InvalidOperationException();
}