Enumerable.Intersect Method
Definition
Important
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Produces the set intersection of two sequences.
Overloads
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) |
Produces the set intersection of two sequences by using the default equality comparer to compare values. |
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) |
Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values. |
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
- Source:
- Intersect.cs
- Source:
- Intersect.cs
- Source:
- Intersect.cs
Produces the set intersection of two sequences by using the default equality comparer to compare values.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static System::Collections::Generic::IEnumerable<TSource> ^ Intersect(System::Collections::Generic::IEnumerable<TSource> ^ first, System::Collections::Generic::IEnumerable<TSource> ^ second);
public static System.Collections.Generic.IEnumerable<TSource> Intersect<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second);
static member Intersect : seq<'Source> * seq<'Source> -> seq<'Source>
<Extension()>
Public Function Intersect(Of TSource) (first As IEnumerable(Of TSource), second As IEnumerable(Of TSource)) As IEnumerable(Of TSource)
Type Parameters
- TSource
The type of the elements of the input sequences.
Parameters
- first
- IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in second
will be returned.
- second
- IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in the first sequence will be returned.
Returns
A sequence that contains the elements that form the set intersection of two sequences.
Exceptions
first
or second
is null
.
Examples
The following code example demonstrates how to use Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
to return the elements that appear in each of two sequences of integers.
int[] id1 = { 44, 26, 92, 30, 71, 38 };
int[] id2 = { 39, 59, 83, 47, 26, 4, 30 };
IEnumerable<int> both = id1.Intersect(id2);
foreach (int id in both)
Console.WriteLine(id);
/*
This code produces the following output:
26
30
*/
' Create two integer arrays.
Dim id1() As Integer = {44, 26, 92, 30, 71, 38}
Dim id2() As Integer = {39, 59, 83, 47, 26, 4, 30}
' Find the set intersection of the two arrays.
Dim intersection As IEnumerable(Of Integer) = id1.Intersect(id2)
Dim output As New System.Text.StringBuilder
For Each id As Integer In intersection
output.AppendLine(id)
Next
' Display the output.
Console.WriteLine(output.ToString)
' This code produces the following output:
'
' 26
' 30
If you want to compare sequences of objects of some custom data type, you have to implement the IEquatable<T> generic interface in a helper class. The following code example shows how to implement this interface in a custom data type and override GetHashCode and Equals methods.
public class ProductA : IEquatable<ProductA>
{
public string Name { get; set; }
public int Code { get; set; }
public bool Equals(ProductA other)
{
if (other is null)
return false;
return this.Name == other.Name && this.Code == other.Code;
}
public override bool Equals(object obj) => Equals(obj as ProductA);
public override int GetHashCode() => (Name, Code).GetHashCode();
}
Public Class ProductA
Inherits IEquatable(Of ProductA)
Public Property Name As String
Public Property Code As Integer
Public Function Equals(ByVal other As ProductA) As Boolean
If other Is Nothing Then Return False
Return Me.Name = other.Name AndAlso Me.Code = other.Code
End Function
Public Overrides Function Equals(ByVal obj As Object) As Boolean
Return Equals(TryCast(obj, ProductA))
End Function
Public Overrides Function GetHashCode() As Integer
Return (Name, Code).GetHashCode()
End Function
End Class
After you implement this interface, you can use sequences of ProductA
objects in the Intersect
method, as shown in the following example:
ProductA[] store1 = { new ProductA { Name = "apple", Code = 9 },
new ProductA { Name = "orange", Code = 4 } };
ProductA[] store2 = { new ProductA { Name = "apple", Code = 9 },
new ProductA { Name = "lemon", Code = 12 } };
Dim store1() As ProductA =
{New Product With {.Name = "apple", .Code = 9},
New Product With {.Name = "orange", .Code = 4}}
Dim store2() As ProductA =
{New Product With {.Name = "apple", .Code = 9},
New Product With {.Name = "lemon", .Code = 12}}
// Get the products from the first array
// that have duplicates in the second array.
IEnumerable<ProductA> duplicates =
store1.Intersect(store2);
foreach (var product in duplicates)
Console.WriteLine(product.Name + " " + product.Code);
/*
This code produces the following output:
apple 9
*/
' Get the products from the first array
' that have duplicates in the second array.
Dim duplicates = store1.Intersect(store2)
For Each product In duplicates
Console.WriteLine(product.Name & " " & product.Code)
Next
' This code produces the following output:
'
' apple 9
'
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 intersection of two sets A and B is defined as the set that contains all the elements of A that also appear in B, but no other elements.
When the object returned by this method is enumerated, Intersect
yields distinct elements occurring in both sequences in the order in which they appear in first
.
The default equality comparer, Default, is used to compare values of the types. To compare a custom data type, you need to override the Equals and the GetHashCode methods, and optionally implement the IEquatable<T> generic interface in the custom type. For more information, see the Default property.
Applies to
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
- Source:
- Intersect.cs
- Source:
- Intersect.cs
- Source:
- Intersect.cs
Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static System::Collections::Generic::IEnumerable<TSource> ^ Intersect(System::Collections::Generic::IEnumerable<TSource> ^ first, System::Collections::Generic::IEnumerable<TSource> ^ second, System::Collections::Generic::IEqualityComparer<TSource> ^ comparer);
public static System.Collections.Generic.IEnumerable<TSource> Intersect<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second, System.Collections.Generic.IEqualityComparer<TSource> comparer);
public static System.Collections.Generic.IEnumerable<TSource> Intersect<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second, System.Collections.Generic.IEqualityComparer<TSource>? comparer);
static member Intersect : seq<'Source> * seq<'Source> * System.Collections.Generic.IEqualityComparer<'Source> -> seq<'Source>
<Extension()>
Public Function Intersect(Of TSource) (first As IEnumerable(Of TSource), second As IEnumerable(Of TSource), comparer As IEqualityComparer(Of TSource)) As IEnumerable(Of TSource)
Type Parameters
- TSource
The type of the elements of the input sequences.
Parameters
- first
- IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in second
will be returned.
- second
- IEnumerable<TSource>
An IEnumerable<T> whose distinct elements that also appear in the first sequence will be returned.
- comparer
- IEqualityComparer<TSource>
An IEqualityComparer<T> to compare values.
Returns
A sequence that contains the elements that form the set intersection of two sequences.
Exceptions
first
or second
is null
.
Examples
The following example shows how to implement an equality comparer that can be used in the Intersect
method.
public class Product
{
public string Name { get; set; }
public int Code { get; set; }
}
// Custom comparer for the Product class
class ProductComparer : IEqualityComparer<Product>
{
// Products are equal if their names and product numbers are equal.
public bool Equals(Product x, Product y)
{
//Check whether the compared objects reference the same data.
if (Object.ReferenceEquals(x, y)) return true;
//Check whether any of the compared objects is null.
if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
return false;
//Check whether the products' properties are equal.
return x.Code == y.Code && x.Name == y.Name;
}
// If Equals() returns true for a pair of objects
// then GetHashCode() must return the same value for these objects.
public int GetHashCode(Product product)
{
//Check whether the object is null
if (Object.ReferenceEquals(product, null)) return 0;
//Get hash code for the Name field if it is not null.
int hashProductName = product.Name == null ? 0 : product.Name.GetHashCode();
//Get hash code for the Code field.
int hashProductCode = product.Code.GetHashCode();
//Calculate the hash code for the product.
return hashProductName ^ hashProductCode;
}
}
Public Class Product
Public Property Name As String
Public Property Code As Integer
End Class
' Custom comparer for the Product class
Public Class ProductComparer
Implements IEqualityComparer(Of Product)
Public Function Equals1(
ByVal x As Product,
ByVal y As Product
) As Boolean Implements IEqualityComparer(Of Product).Equals
' Check whether the compared objects reference the same data.
If x Is y Then Return True
'Check whether any of the compared objects is null.
If x Is Nothing OrElse y Is Nothing Then Return False
' Check whether the products' properties are equal.
Return (x.Code = y.Code) AndAlso (x.Name = y.Name)
End Function
Public Function GetHashCode1(
ByVal product As Product
) As Integer Implements IEqualityComparer(Of Product).GetHashCode
' Check whether the object is null.
If product Is Nothing Then Return 0
' Get hash code for the Name field if it is not null.
Dim hashProductName =
If(product.Name Is Nothing, 0, product.Name.GetHashCode())
' Get hash code for the Code field.
Dim hashProductCode = product.Code.GetHashCode()
' Calculate the hash code for the product.
Return hashProductName Xor hashProductCode
End Function
End Class
After you implement this comparer, you can use sequences of Product
objects in the Intersect
method, as shown in the following example:
Product[] store1 = { new Product { Name = "apple", Code = 9 },
new Product { Name = "orange", Code = 4 } };
Product[] store2 = { new Product { Name = "apple", Code = 9 },
new Product { Name = "lemon", Code = 12 } };
// Get the products from the first array
// that have duplicates in the second array.
IEnumerable<Product> duplicates =
store1.Intersect(store2, new ProductComparer());
foreach (var product in duplicates)
Console.WriteLine(product.Name + " " + product.Code);
/*
This code produces the following output:
apple 9
*/
Dim store1() As Product =
{New Product With {.Name = "apple", .Code = 9},
New Product With {.Name = "orange", .Code = 4}}
Dim store2() As Product =
{New Product With {.Name = "apple", .Code = 9},
New Product With {.Name = "lemon", .Code = 12}}
' Get the products from the first array
' that have duplicates in the second array.
Dim duplicates = store1.Intersect(store2, New ProductComparer())
For Each product In duplicates
Console.WriteLine(product.Name & " " & product.Code)
Next
' This code produces the following output:
'
' apple 9
'
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 intersection of two sets A and B is defined as the set that contains all the elements of A that also appear in B, but no other elements.
When the object returned by this method is enumerated, Intersect
yields distinct elements occurring in both sequences in the order in which they appear in first
.
If comparer
is null
, the default equality comparer, Default, is used to compare values.
See also
Applies to
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