• It is an on-demand loading which provides an efficient technique to improve performance.
  • The opposite of lazy loading is eager loading.

Lazy Initialization

• With lazy initialization, the object to be lazily loaded is initially set to null.
• Every request for the object checks for null and creates it "on the fly" before returning it first.
• This method is the simplest to implement.
  • However, if null is a legitimate return value, it may be necessary to use a placeholder object to signal that it has not been initialized.

private Widget _MyWidget = null;
public Widget MyWidget
{
	get 
	{
		if (_MyWidget == null)
			_MyWidget = Widget.Load();
		return _MyWidget;
	}
	// Or with the null-coalescing operator ??
	// get => _MyWidget ?? Widget.Load();
}

Value Holder

• A value holder is a generic object that handles the lazy loading behavior, and appears in place of the object's data fields.
• Lazy<T> class implements a generic value holder.

private ValueHolder<Widget> valueHolder;
public Widget MyWidget => valueHolder.GetValue();

Ghost

• A "ghost" is the object that is to be loaded in a partial state.
• It may only contain the object's identifier, but it loads its own data the first time one of its properties is accessed.

Virtual Proxy

• Virtual Proxy is an object with the same interface as the real object.
• The first time one of its methods is called it loads the real object and then delegates.
• The proxy actually is not virtual, but it is dynamic and it follows real proxy pattern.
• The virtual proxy is mostly used in ORM tools.
  • It derives from the entity and overrides navigation properties.
  • The proxy holds a state of navigation property in private field or any more complex structure.
  • If the property is accessed first time it sees that the state is unloaded and triggers loading from database and change the state to loaded.