TEnumerable.GroupBy<T,TKey,TElement,TResult> Method

Unit:: Spring.Collections

Package:: Spring.Base

Overloads

GroupBy<T,TKey>(IEnumerable<T>, Func<T,TKey>)	Groups the elements of a sequence according to a specified key selector function.
GroupBy<T,TKey>(IEnumerable<T>, Func<T,TKey>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.
GroupBy<T,TKey,TElement>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>)	Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.
GroupBy<T,TKey,TElement>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.
GroupBy<T,TKey,TResult>(IEnumerable<T>, Func<T,TKey>, Func<TKey,IEnumerable<T>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.
GroupBy<T,TKey,TResult>(IEnumerable<T>, Func<T,TKey>, Func<TKey,IEnumerable<T>,TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.
GroupBy<T,TKey,TElement,TResult>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.
GroupBy<T,TKey,TElement,TResult>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

GroupBy<T,TKey>(IEnumerable<T>, Func<T,TKey>)

Groups the elements of a sequence according to a specified key selector function.

Delphi

class function GroupBy<T,TKey>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>): IEnumerable<IGrouping<TKey,T>>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

Returns

IEnumerable<IGrouping<TKey, T>>

A sequence where each element is a group that contains a sequence of elements and a key.

Exceptions

source or keySelector is nil .

GroupBy<T,TKey>(IEnumerable<T>, Func<T,TKey>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

Delphi

class function GroupBy<T,TKey>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const comparer: IEqualityComparer<TKey>): IEnumerable<IGrouping<TKey,T>>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

comparer: IEqualityComparer<TKey>

An equality comparer to compare keys.

Returns

IEnumerable<IGrouping<TKey, T>>

A sequence where each element is a group that contains a collection of elements and a key.

Exceptions

source or keySelector is nil .

Remarks

If comparer is nil , the default equality comparer is used to compare keys.

GroupBy<T,TKey,TElement>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>)

Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

Delphi

class function GroupBy<T,TKey,TElement>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const elementSelector: Func<T, TElement>): IEnumerable<IGrouping<TKey,TElement>>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TElement

The type of the elements in the grouping.

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

elementSelector: Func<T, TElement>

A function to map each source element to an element in the grouping.

Returns

IEnumerable<IGrouping<TKey, TElement>>

A sequence where each element is a group that contains a collection of elements of type TElement and a key.

Exceptions

source or keySelector or elementSelector is nil .

GroupBy<T,TKey,TElement>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.

Delphi

class function GroupBy<T,TKey,TElement>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const elementSelector: Func<T, TElement>; const comparer: IEqualityComparer<TKey>): IEnumerable<IGrouping<TKey,TElement>>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TElement

The type of the elements in the grouping.

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

elementSelector: Func<T, TElement>

A function to map each source element to an element in the grouping.

comparer: IEqualityComparer<TKey>

An equality comparer to compare keys.

Returns

IEnumerable<IGrouping<TKey, TElement>>

A sequence where each element is a group that contains a collection of elements of type TElement and a key.

Exceptions

source or keySelector or elementSelector is nil .

Remarks

If comparer is nil , the default equality comparer is used to compare keys.

GroupBy<T,TKey,TResult>(IEnumerable<T>, Func<T,TKey>, Func<TKey,IEnumerable<T>,TResult>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

Delphi

class function GroupBy<T,TKey,TResult>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const resultSelector: Func<TKey, IEnumerable<T>, TResult>): IEnumerable<TResult>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TResult

The type of the result value returned by resultSelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

resultSelector: Func<TKey, IEnumerable<T>, TResult>

A function to create a result value from each group.

Returns

IEnumerable<TResult>

A collection of elements of type TResult where each element represents a projection over a group and its key.

Exceptions

source or keySelector or resultSelector is nil .

GroupBy<T,TKey,TResult>(IEnumerable<T>, Func<T,TKey>, Func<TKey,IEnumerable<T>,TResult>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.

Delphi

class function GroupBy<T,TKey,TResult>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const resultSelector: Func<TKey, IEnumerable<T>, TResult>; const comparer: IEqualityComparer<TKey>): IEnumerable<TResult>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TResult

The type of the result value returned by resultSelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

resultSelector: Func<TKey, IEnumerable<T>, TResult>

A function to create a result value from each group.

comparer: IEqualityComparer<TKey>

An equality comparer to compare keys.

Returns

IEnumerable<TResult>

A collection of elements of type TResult where each element represents a projection over a group and its key.

Exceptions

source or keySelector or resultSelector is nil .

Remarks

If comparer is nil , the default equality comparer is used to compare keys.

GroupBy<T,TKey,TElement,TResult>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.

Delphi

class function GroupBy<T,TKey,TElement,TResult>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const elementSelector: Func<T, TElement>; const resultSelector: Func<TKey, IEnumerable<TElement>, TResult>): IEnumerable<TResult>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TElement

The type of the elements in each grouping.

TResult

The type of the result value returned by resultSelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

elementSelector: Func<T, TElement>

A function to map each source element to an element in a grouping.

resultSelector: Func<TKey, IEnumerable<TElement>, TResult>

A function to create a result value from each group.

Returns

IEnumerable<TResult>

A collection of elements of type TResult where each element represents a projection over a group and its key.

Exceptions

source or keySelector or elementSelector or resultSelector is nil .

GroupBy<T,TKey,TElement,TResult>(IEnumerable<T>, Func<T,TKey>, Func<T,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

Delphi

class function GroupBy<T,TKey,TElement,TResult>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>; const elementSelector: Func<T, TElement>; const resultSelector: Func<TKey, IEnumerable<TElement>, TResult>; const comparer: IEqualityComparer<TKey>): IEnumerable<TResult>

Type Parameters

T

The type of the elements of source .

TKey

The type of the key returned by keySelector .

TElement

The type of the elements in each grouping.

TResult

The type of the result value returned by resultSelector .

Parameters

source: IEnumerable<T>

A sequence whose elements to group.

keySelector: Func<T, TKey>

A function to extract the key for each element.

elementSelector: Func<T, TElement>

A function to map each source element to an element in a grouping.

resultSelector: Func<TKey, IEnumerable<TElement>, TResult>

A function to create a result value from each group.

comparer: IEqualityComparer<TKey>

An equality comparer to compare keys.

Returns

IEnumerable<TResult>

A collection of elements of type TResult where each element represents a projection over a group and its key.

Exceptions

source or keySelector or elementSelector or resultSelector is nil .

Remarks

If comparer is nil , the default equality comparer is used to compare keys.