IEnumerableExtensionPrefOrNullTSource(IEnumerableTSource, FuncTSource, Boolean, Boolean) Method

public static TSource PrefOrNull<TSource>(
	this IEnumerable<TSource>? values,
	Func<TSource, bool>? filter,
	bool skipEmptyItems = true
)
where TSource : VCardProperty

<ExtensionAttribute>
Public Shared Function PrefOrNull(Of TSource As VCardProperty) ( 
	values As IEnumerable(Of TSource),
	filter As Func(Of TSource, Boolean),
	Optional skipEmptyItems As Boolean = true
) As TSource

public:
[ExtensionAttribute]
generic<typename TSource>
where TSource : VCardProperty
static TSource PrefOrNull(
	IEnumerable<TSource>^ values, 
	Func<TSource, bool>^ filter, 
	bool skipEmptyItems = true
)

[<ExtensionAttribute>]
static member PrefOrNull : 
        values : IEnumerable<'TSource> * 
        filter : Func<'TSource, bool> * 
        ?skipEmptyItems : bool 
(* Defaults:
        let _skipEmptyItems = defaultArg skipEmptyItems true
*)
-> 'TSource  when 'TSource : VCardProperty

Parameters

values  IEnumerableTSource

The IEnumerableT of VCardProperty objects to search. The collection may be null, empty, or may contain null references.

filter  FuncTSource, Boolean

A FuncT, TResult which allows additional filtering of the items, or null to not perform additional filtering. The arguments of the delegate are guaranteed to not be null.

skipEmptyItems  Boolean  (Optional)

Pass false to include empty items in the return value. ("Empty" means that IsEmpty returns true.) null values will always be ignored.

Type Parameters

TSource

Generic type parameter that's constrained to be a class that's derived from VCardProperty.

Return Value

The most preferred VCardProperty from values that passes the filter, or null if no such item could be found. This happens in any case

• if values is null,
• if values is empty,
• if values contains only null references,
• or if values contains only empty items and skipEmptyItems is true.

"Most preferred" is defined as the VCardProperty with the lowest Preference value.

Usage Note

Reference