ToDictionary(TSource, TKey, TElement) Method (IEnumerable(TSource), Func(TSource, TKey), Func(TSource, TElement), IEqualityComparer(TKey))

Enumerable.ToDictionary(Of TSource, TKey, TElement) Method (IEnumerable(Of TSource), Func(Of TSource, TKey), Func(Of TSource, TElement), IEqualityComparer(Of TKey))

Creates a Dictionary(Of TKey, TValue) from an IEnumerable(Of T) according to a specified key selector function, a comparer, and an element selector function.

Namespace:  System.Linq
Assembly:  System.Core (in System.Core.dll)

<ExtensionAttribute> _
Public Shared Function ToDictionary(Of TSource, TKey, TElement) ( _
	source As IEnumerable(Of TSource), _
	keySelector As Func(Of TSource, TKey), _
	elementSelector As Func(Of TSource, TElement), _
	comparer As IEqualityComparer(Of TKey) _
) As Dictionary(Of TKey, TElement)

Type Parameters


The type of the elements of source.


The type of the key returned by keySelector.


The type of the value returned by elementSelector.


Type: System.Collections.Generic.IEnumerable(Of TSource)
An IEnumerable(Of T) to create a Dictionary(Of TKey, TValue) from.
Type: System.Func(Of TSource, TKey)
A function to extract a key from each element.
Type: System.Func(Of TSource, TElement)
A transform function to produce a result element value from each element.
Type: System.Collections.Generic.IEqualityComparer(Of TKey)
An IEqualityComparer(Of T) to compare keys.

Return Value

Type: System.Collections.Generic.Dictionary(Of TKey, TElement)
A Dictionary(Of TKey, TValue) that contains values of type TElement selected from the input sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of TSource). When you use instance method syntax to call this method, omit the first parameter.


source or keySelector or elementSelector is Nothing.


keySelector produces a key that is Nothing.


keySelector produces duplicate keys for two elements.

If comparer is Nothing, the default equality comparer Default is used to compare keys.


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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