Queryable.CountBy<TSource,TKey> Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Returns the count of each element from a sequence according to a specified key selector function.
public static System.Linq.IQueryable<System.Collections.Generic.KeyValuePair<TKey,int>> CountBy<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = default);static member CountBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.IQueryable<System.Collections.Generic.KeyValuePair<'Key, int>><Extension()>
Public Function CountBy(Of TSource, TKey) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), Optional comparer As IEqualityComparer(Of TKey) = Nothing) As IQueryable(Of KeyValuePair(Of TKey, Integer))Type Parameters
- TSource
The type of the elements of source.
- TKey
The type of key to distinguish elements by.
Parameters
- source
- IQueryable<TSource>
The sequence to count elements from.
- keySelector
- Expression<Func<TSource,TKey>>
A function to extract the key for each element.
- comparer
- IEqualityComparer<TKey>
An IEqualityComparer<T> to compare keys.
Returns
An IQueryable<T> that contains count for each distinct elements from the source sequence as a KeyValuePair<TKey,TValue> object.
Exceptions
source is null.
Applies to
Collaborate with us on GitHub
The source for this content can be found on GitHub, where you can also create and review issues and pull requests. For more information, see our contributor guide.
