Enumerable.LeftJoin Method

Source:

LeftJoin.cs

Source:

LeftJoin.cs

public:
generic 
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable ^ LeftJoin(System::Collections::Generic::IEnumerable ^ outer, System::Collections::Generic::IEnumerable ^ inner, Func ^ outerKeySelector, Func ^ innerKeySelector, Func ^ resultSelector);

public static System.Collections.Generic.IEnumerable LeftJoin(this System.Collections.Generic.IEnumerable outer, System.Collections.Generic.IEnumerable inner, Func outerKeySelector, Func innerKeySelector, Func resultSelector);

static member LeftJoin : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> -> seq<'Result>

Public Function LeftJoin(Of TOuter, TInner, TKey, TResult) (outer As IEnumerable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Func(Of TOuter, TKey), innerKeySelector As Func(Of TInner, TKey), resultSelector As Func(Of TOuter, TInner, TResult)) As IEnumerable(Of TResult)

Type Parameters

Parameters

Returns

An IEnumerable that has elements of type TResult that are obtained by performing a left outer join on two sequences.

Exceptions

Remarks

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in C# or For Each in Visual Basic.

The default equality comparer, Default, is used to hash and compare keys.

A join refers to the operation of correlating the elements of two sources of information based on a common key.

LeftJoin(IEnumerable, IEnumerable, Func, Func, Func) brings the two information sources and the keys by which they are matched together in one method call.

In relational database terms, the LeftJoin(IEnumerable, IEnumerable, Func, Func, Func) method implements an outer left equijoin.

'Outer left' means that elements of the first sequence are returned regardless of whether matching elements are found in the other sequence.

An 'equijoin' is a join in which the keys are compared for equality.

An inner join - where only elements that have a match in the other sequence are included in the results - can be performed using the Join(IEnumerable, IEnumerable, Func, Func, Func) method.

For more information, see Join operations.

Source:

LeftJoin.cs

Source:

LeftJoin.cs

public:
generic 
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable ^ LeftJoin(System::Collections::Generic::IEnumerable ^ outer, System::Collections::Generic::IEnumerable ^ inner, Func ^ outerKeySelector, Func ^ innerKeySelector, Func ^ resultSelector, System::Collections::Generic::IEqualityComparer ^ comparer);

public static System.Collections.Generic.IEnumerable LeftJoin(this System.Collections.Generic.IEnumerable outer, System.Collections.Generic.IEnumerable inner, Func outerKeySelector, Func innerKeySelector, Func resultSelector, System.Collections.Generic.IEqualityComparer? comparer);

static member LeftJoin : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>

Public Function LeftJoin(Of TOuter, TInner, TKey, TResult) (outer As IEnumerable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Func(Of TOuter, TKey), innerKeySelector As Func(Of TInner, TKey), resultSelector As Func(Of TOuter, TInner, TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

Type Parameters

Parameters

Returns

An IEnumerable that has elements of type TResult that are obtained by performing a left outer join on two sequences.

Exceptions

Remarks

This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in C# or For Each in Visual Basic.

The default equality comparer, Default, is used to hash and compare keys.

A join refers to the operation of correlating the elements of two sources of information based on a common key.

LeftJoin(IEnumerable, IEnumerable, Func, Func, Func, IEqualityComparer) brings the two information sources and the keys by which they are matched together in one method call.

In relational database terms, the LeftJoin(IEnumerable, IEnumerable, Func, Func, Func, IEqualityComparer) method implements an outer left equijoin.

'Outer left' means that elements of the first sequence are returned regardless of whether matching elements are found in the other sequence.

An 'equijoin' is a join in which the keys are compared for equality.

An inner join - where only elements that have a match in the other sequence are included in the results - can be performed using the Join(IEnumerable, IEnumerable, Func, Func, Func, IEqualityComparer) method.

For more information, see Join operations.

Source:

LeftJoin.cs

public static System.Collections.Generic.IEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin(this System.Collections.Generic.IEnumerable outer, System.Collections.Generic.IEnumerable inner, Func outerKeySelector, Func innerKeySelector, System.Collections.Generic.IEqualityComparer? comparer = default);

static member LeftJoin : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * System.Collections.Generic.IEqualityComparer<'Key> -> seq>

Public Function LeftJoin(Of TOuter, TInner, TKey) (outer As IEnumerable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Func(Of TOuter, TKey), innerKeySelector As Func(Of TInner, TKey), Optional comparer As IEqualityComparer(Of TKey) = Nothing) As IEnumerable(Of ValueTuple(Of TOuter, TInner))

Type Parameters

Parameters

Returns