Method InnerMergeJoin
| Edit this page View SourceInnerMergeJoin<TLeft, TRight, TKey>(IEnumerable<TLeft>, IEnumerable<TRight>, Func<TLeft, TKey>, Func<TRight, TKey>, IComparer<TKey>?)
Performs an inner join on two heterogeneous sequences.
Declaration
public static IEnumerable<(TLeft Left, TRight Right)> InnerMergeJoin<TLeft, TRight, TKey>(this IEnumerable<TLeft> left, IEnumerable<TRight> right, Func<TLeft, TKey> leftKeySelector, Func<TRight, TKey> rightKeySelector, IComparer<TKey>? comparer = null)
Parameters
Type | Name | Description |
---|---|---|
IEnumerable<TLeft> | left | The first sequence. |
IEnumerable<TRight> | right | The second sequence. |
Func<TLeft, TKey> | leftKeySelector | A function to extract the join key from each element of the first sequence. |
Func<TRight, TKey> | rightKeySelector | A function to extract the join key from each element of the second sequence. |
IComparer<TKey> | comparer | An IEqualityComparer<T> to hash and compare keys. |
Returns
Type | Description |
---|---|
IEnumerable<(TLeft Left, TRight Right)> | A sequence containing values from an inner join of the two input sequences. |
Type Parameters
Name | Description |
---|---|
TLeft | The type of elements in the first sequence. |
TRight | The type of elements in the second sequence. |
TKey | The type of the key returned by the key selector functions. |
Remarks
The result of this method is an `inner`-join. Values are only returned if matching elements are found in
both left
and right
sequences.
This method is implemented using a `merge`-join. The sequences left
and right
are assumed to be already sorted. Results from using unsorted sequences with this method are
undefined. Each sequence is enumerated exactly once in a parallel fashion, until both sequences are
fully enumerated.
This method uses deferred execution and streams its results.
Examples
The following code example demonstrates how to execute an inner merge join of two sequences using InnerMergeJoin
.
var people = new Person[]
{
new("John Doe", 1),
new("Jane Doe", 6),
new("Lucy Ricardo", 4),
new("Ricky Ricardo", 2),
new("Fred Mertz", 3),
new("Ethel Mertz", 5),
};
var pets = new Pet[]
{
new("Bear", 8),
new("Polly", 2),
new("Minnie", 2),
new("Mittens", 1),
new("Patches", 1),
new("Paws", 1),
};
var results = people.OrderBy(p => p.PersonId)
.InnerMergeJoin(
pets.OrderBy(p => p.PersonId),
p => p.PersonId,
p => p.PersonId);
foreach (var (person, pet) in results)
{
Console.WriteLine($"({person.Name}, {pet?.Name})");
}
// This code produces the following output:
// (John Doe, Mittens)
// (John Doe, Patches)
// (John Doe, Paws)
// (Ricky Ricardo, Polly)
// (Ricky Ricardo, Minnie)
record Person(string Name, int PersonId);
record Pet(string Name, int PersonId);
Exceptions
Type | Condition |
---|---|
ArgumentNullException |
|
InnerMergeJoin<TLeft, TRight, TKey, TResult>(IEnumerable<TLeft>, IEnumerable<TRight>, Func<TLeft, TKey>, Func<TRight, TKey>, Func<TLeft, TRight, TResult>, IComparer<TKey>?)
Performs an inner join on two heterogeneous sequences.
Declaration
public static IEnumerable<TResult> InnerMergeJoin<TLeft, TRight, TKey, TResult>(this IEnumerable<TLeft> left, IEnumerable<TRight> right, Func<TLeft, TKey> leftKeySelector, Func<TRight, TKey> rightKeySelector, Func<TLeft, TRight, TResult> bothResultSelector, IComparer<TKey>? comparer = null)
Parameters
Type | Name | Description |
---|---|---|
IEnumerable<TLeft> | left | The first sequence. |
IEnumerable<TRight> | right | The second sequence. |
Func<TLeft, TKey> | leftKeySelector | A function to extract the join key from each element of the first sequence. |
Func<TRight, TKey> | rightKeySelector | A function to extract the join key from each element of the second sequence. |
Func<TLeft, TRight, TResult> | bothResultSelector | A function to create a result element from two matching elements. |
IComparer<TKey> | comparer | An IEqualityComparer<T> to hash and compare keys. |
Returns
Type | Description |
---|---|
IEnumerable<TResult> | A sequence containing results projected from an inner join of the two input sequences. |
Type Parameters
Name | Description |
---|---|
TLeft | The type of elements in the first sequence. |
TRight | The type of elements in the second sequence. |
TKey | The type of the key returned by the key selector functions. |
TResult | The type of the result elements. |
Remarks
The result of this method is an `inner`-join. Values are projected using bothResultSelector
only if matching elements are found in both left
and
right
sequences.
This method is implemented using a `merge`-join. The sequences left
and right
are assumed to be already sorted. Results from using unsorted sequences with this method are
undefined. Each sequence is enumerated exactly once in a parallel fashion, until both sequences are
fully enumerated.
This method uses deferred execution and streams its results.
Examples
The following code example demonstrates how to execute an inner merge join of two sequences using InnerMergeJoin
.
var people = new Person[]
{
new("John Doe", 1),
new("Jane Doe", 6),
new("Lucy Ricardo", 4),
new("Ricky Ricardo", 2),
new("Fred Mertz", 3),
new("Ethel Mertz", 5),
};
var pets = new Pet[]
{
new("Bear", 8),
new("Polly", 2),
new("Minnie", 2),
new("Mittens", 1),
new("Patches", 1),
new("Paws", 1),
};
var results = people.OrderBy(p => p.PersonId)
.InnerMergeJoin(
pets.OrderBy(p => p.PersonId),
p => p.PersonId,
p => p.PersonId,
(person, pet) => $"({person.Name}, {pet.Name})");
foreach (var str in results)
Console.WriteLine(str);
// This code produces the following output:
// (John Doe, Mittens)
// (John Doe, Patches)
// (John Doe, Paws)
// (Ricky Ricardo, Polly)
// (Ricky Ricardo, Minnie)
record Person(string Name, int PersonId);
record Pet(string Name, int PersonId);
Exceptions
Type | Condition |
---|---|
ArgumentNullException |
|