The default value is null.
Application developeres may specify a UIKit.UISearchDisplayController using Interface Builder or programmatically. To assign the UIViewController.SearchDisplayController property, the UIKit.UIViewController must have a field of type UIKit.UISearchBar decorated with [Outlet] (Foundation.OutletAttribute) and must initialize a new UIKit.UISearchDisplayController with a reference to that UIKit.UISearchBar. As shown in the following code, the assignment of the UIKit.UISearchDisplayController to UIViewControlle.SearchDisplayController is done implicitly during initialization, and does not involve the application developer assigning the reference to the newly-created UIKit.UISearchDisplayController:
C# Example
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
//this.SearchDisplayController == null
//n.b.: No assignment
new UISearchDisplayController (mySearchBar, this);
//this.SearchDisplayController != null
Console.WriteLine ("SearchDisplayController = '{0}'", this.SearchDisplayController);
}