Enumerable.ToDictionary<TSource, TKey> Method (IEnumerable<TSource>, Func<TSource, TKey>, IEqualityComparer<TKey>)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.
Assembly: System.Core (in System.Core.dll)
public static Dictionary<TKey, TSource> ToDictionary<TSource, TKey>( this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer )
Type Parameters
- TSource
The type of the elements of source.
- TKey
The type of the keys 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.
- comparer
- Type: System.Collections.Generic.IEqualityComparer<TKey>
An IEqualityComparer<T> to compare keys.
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.| Exception | Condition |
|---|---|
| ArgumentNullException | source or keySelector is null. -or- keySelector produces a key that is null. |
| ArgumentException | keySelector produces duplicate keys for two elements. |
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