Enumerable::ToDictionary<TSource, TKey> Method (IEnumerable<TSource>, Func<TSource, TKey>)

Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function.

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

[ExtensionAttribute]
public:
generic<typename TSource, typename TKey>
static Dictionary<TKey, TSource>^ ToDictionary(
	IEnumerable<TSource>^ source, 
	Func<TSource, TKey>^ keySelector
)

Type Parameters

TSource

The type of the elements of source.

TKey

The type of the key returned by keySelector.

Parameters

source
Type: System.Collections.Generic::IEnumerable<TSource>

An IEnumerable<T> to create a Dictionary<TKey, TValue> from.

keySelector
Type: System::Func<TSource, TKey>

A function to extract a key from each element.

Return Value

Type: System.Collections.Generic::Dictionary<TKey, TSource>
A Dictionary<TKey, TValue> that contains keys and values.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<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
ArgumentNullException

source or keySelector is nullptr.

-or-

keySelector produces a key that is nullptr.

ArgumentException

keySelector produces duplicate keys for two elements.

The ToDictionary<TSource, TKey>(IEnumerable<TSource>, Func<TSource, TKey>) method uses the default equality comparer Default to compare keys.

The following code example demonstrates how to use ToDictionary<TSource, TKey>(IEnumerable<TSource>, Func<TSource, TKey>) to create a Dictionary<TKey, TValue> by using a key selector.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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