Add<TKey>(Expression<Func<T,TKey>>,Boolean) Method

Creates a new subindex and attaches it to its parent's IndexDefinition<T>.Subindexes collection.

Syntax

Visual Basic
C#

'Declaration
 
Public Overloads Function Add(Of TKey)( _
   ByVal keySelector As System.Linq.Expressions.Expression(Of Func(Of T,TKey)), _
   ByVal keyIsUnique As System.Boolean _
) As Subindex(Of T,TKey)

public Subindex<T,TKey> Add<TKey>( 
   System.Linq.Expressions.Expression<Func<T,TKey>> keySelector,
   System.bool keyIsUnique
)

Parameters

keySelector: Key selector expression of the subindex, see KeySelector.
keyIsUnique: 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 IndexDefinition<T>.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 System.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.

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

SubindexCollection<T> Class
SubindexCollection<T> Members
Overload List