Creates a new subindex and attaches it to its parent's Subindexes collection.

Namespace:  C1.LiveLinq.Indexing
Assembly:  C1.LiveLinq (in C1.LiveLinq.dll)

Syntax

C#
public Subindex<T, TKey> Add<TKey>(
	Expression<Func<T, TKey>> keySelector,
	bool keyIsUnique
)
Visual Basic
Public Function Add(Of TKey) ( _
	keySelector As Expression(Of Func(Of T, TKey)), _
	keyIsUnique As Boolean _
) As Subindex(Of T, TKey)

Parameters

keySelector
Type: System.Linq.Expressions..::..Expression<(Of <(<'Func<(Of <(<'T, TKey>)>)>>)>)>
Key selector expression of the subindex, see KeySelector.
keyIsUnique
Type: System..::..Boolean
Specifies whether the key used in this subindex is unique for any given value of the parent key (default: false).

Type Parameters

TKey
The type of the subindex key.

Return Value

The new subindex added to its parent's Subindexes collection.

Remarks

A unique index occupies less memory and performs better than a non-unique index (although the difference isn't dramatic). Therefore, for unique keys, it's recommended to specify the corresponding index as unique.

But do that only if you are sure that the key is indeed unique, as it imposes a uniqueness constraint on the indexed collection. An attempt to modify the indexed collection violating the uniqueness throws an InvalidOperationException.

For a subindex, uniqueness means that any given pair of parent key and subindex key values uniquely determines an item in the indexed collection.

See Also