ParallelEnumerable.ToDictionary<TSource, TKey, TElement> Method (ParallelQuery<TSource>, Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)

Creates a Dictionary<TKey, TValue> from a ParallelQuery<TSource> according to a specified key selector function, a comparer, and an element selector function.

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

public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement>(
	this ParallelQuery<TSource> source,
	Func<TSource, TKey> keySelector,
	Func<TSource, TElement> elementSelector,
	IEqualityComparer<TKey> comparer
)

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by keySelector.

TElement

The type of the value returned by elementSelector.

Parameters

source
Type: System.Linq.ParallelQuery<TSource>
A sequence to create a Dictionary<TKey, TValue> from.
keySelector
Type: System.Func<TSource, TKey>
A function to extract a key from each element.
elementSelector
Type: System.Func<TSource, TElement>
A transform function to produce a result element value from each element.
comparer
Type: System.Collections.Generic.IEqualityComparer<TKey>
An IEqualityComparer<T> to compare keys.

Return Value

Type: System.Collections.Generic.Dictionary<TKey, TElement>
A Dictionary<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 ParallelQuery<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
OperationCanceledException

The query was canceled with the token passed in through WithCancellation.

ArgumentNullException

source or keySelector or elementSelector is a null reference (Nothing in Visual Basic).

AggregateException

keySelector produces a key that is a null reference (Nothing in Visual Basic). -or- keySelector produces duplicate keys for two elements. -or- One or more exceptions occurred during the evaluation of the query.

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

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

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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