Enumerable.Distinct Enumerable.Distinct Enumerable.Distinct Enumerable.Distinct Method

定義

シーケンスから一意の要素を返します。Returns distinct elements from a sequence.

オーバーロード

Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>)

既定の等値比較子を使用して値を比較することにより、シーケンスから一意の要素を返します。Returns distinct elements from a sequence by using the default equality comparer to compare values.

Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

指定された IEqualityComparer<T> を使用して値を比較することにより、シーケンスから一意の要素を返します。Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.

注釈

結果のシーケンスは順序付けされていません。The result sequence is unordered.

Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>) Distinct<TSource>(IEnumerable<TSource>)

既定の等値比較子を使用して値を比較することにより、シーケンスから一意の要素を返します。Returns distinct elements from a sequence by using the default equality comparer to compare values.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Distinct(System::Collections::Generic::IEnumerable<TSource> ^ source);
public static System.Collections.Generic.IEnumerable<TSource> Distinct<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);
static member Distinct : seq<'Source> -> seq<'Source>
<Extension()>
Public Function Distinct(Of TSource) (source As IEnumerable(Of TSource)) As IEnumerable(Of TSource)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

重複する要素を削除する対象となるシーケンス。The sequence to remove duplicate elements from.

戻り値

IEnumerable<TSource>

ソース シーケンスの一意の要素を格納する IEnumerable<T>An IEnumerable<T> that contains distinct elements from the source sequence.

例外

次のコード例は、を使用Distinct<TSource>(IEnumerable<TSource>)して整数のシーケンスから一意の要素を返す方法を示しています。The following code example demonstrates how to use Distinct<TSource>(IEnumerable<TSource>) to return distinct elements from a sequence of integers.

List<int> ages = new List<int> { 21, 46, 46, 55, 17, 21, 55, 55 };

IEnumerable<int> distinctAges = ages.Distinct();

Console.WriteLine("Distinct ages:");

foreach (int age in distinctAges)
{
    Console.WriteLine(age);
}

/*
 This code produces the following output:

 Distinct ages:
 21
 46
 55
 17
*/
' Create a list of integers.
Dim ages As New List(Of Integer)(New Integer() _
                             {21, 46, 46, 55, 17, 21, 55, 55})

' Select the unique numbers in the List.
Dim distinctAges As IEnumerable(Of Integer) = ages.Distinct()

Dim output As New System.Text.StringBuilder("Distinct ages:" & vbCrLf)
For Each age As Integer In distinctAges
    output.AppendLine(age)
Next

' Display the output.
MsgBox(output.ToString)

' This code produces the following output:
'
' Distinct ages:
' 21
' 46
' 55
' 17

いくつかのカスタムデータ型のオブジェクトのシーケンスから個別の要素を返す場合は、 IEquatable<T>ジェネリックインターフェイスをクラスに実装する必要があります。If you want to return distinct elements from sequences of objects of some custom data type, you have to implement the IEquatable<T> generic interface in the class. 次のコード例は、カスタムデータ型にこのインターフェイスを実装し、メソッドGetHashCodeEqualsメソッドを提供する方法を示しています。The following code example shows how to implement this interface in a custom data type and provide GetHashCode and Equals methods.

public class Product : IEquatable<Product>
{
    public string Name { get; set; }
    public int Code { get; set; }

    public bool Equals(Product other)
    {

        //Check whether the compared object is null. 
        if (Object.ReferenceEquals(other, null)) return false;

        //Check whether the compared object references the same data. 
        if (Object.ReferenceEquals(this, other)) return true;

        //Check whether the products' properties are equal. 
        return Code.Equals(other.Code) && Name.Equals(other.Name);
    }

    // If Equals() returns true for a pair of objects  
    // then GetHashCode() must return the same value for these objects. 

    public override int GetHashCode()
    {

        //Get hash code for the Name field if it is not null. 
        int hashProductName = Name == null ? 0 : Name.GetHashCode();

        //Get hash code for the Code field. 
        int hashProductCode = Code.GetHashCode();

        //Calculate the hash code for the product. 
        return hashProductName ^ hashProductCode;
    }
}
Public Class Product
    Implements IEquatable(Of Product)

    Public Property Name As String
    Public Property Code As Integer

    Public Function Equals1(
        ByVal other As Product
        ) As Boolean Implements IEquatable(Of Product).Equals

        ' Check whether the compared object is null.
        If other Is Nothing Then Return False

        ' Check whether the compared object references the same data.
        If Me Is Other Then Return True

        ' Check whether the products' properties are equal.
        Return Code.Equals(other.Code) AndAlso Name.Equals(other.Name)
    End Function

    Public Overrides Function GetHashCode() As Integer

        ' Get hash code for the Name field if it is not null.
        Dim hashProductName = If(Name Is Nothing, 0, Name.GetHashCode())

        ' Get hash code for the Code field.
        Dim hashProductCode = Code.GetHashCode()

        ' Calculate the hash code for the product.
        Return hashProductName Xor hashProductCode
    End Function
End Class

このインターフェイスを実装した後、次の例にProduct示すようにDistinct<TSource>(IEnumerable<TSource>) 、メソッドでオブジェクトのシーケンスを使用できます。After you implement this interface, you can use a sequence of Product objects in the Distinct<TSource>(IEnumerable<TSource>) method, as shown in the following example:

Product[] products = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 }, 
                       new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "lemon", Code = 12 } };

//Exclude duplicates.

IEnumerable<Product> noduplicates =
    products.Distinct();

foreach (var product in noduplicates)
    Console.WriteLine(product.Name + " " + product.Code);

/*
    This code produces the following output:
    apple 9 
    orange 4
    lemon 12
*/

Dim products() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}, 
     New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "lemon", .Code = 12}}

' Exclude duplicates.

Dim noduplicates = products.Distinct()

For Each product In noduplicates
    Console.WriteLine(product.Name & " " & product.Code)
Next

' This code produces the following output:
'
' apple 9
' orange 4
' lemon 12
' 

注釈

このメソッドは、遅延実行を使用して実装されます。This method is implemented by using deferred execution. イミディエイトの戻り値は、アクションを実行するために必要なすべての情報を格納するオブジェクトです。The immediate return value is an object that stores all the information that is required to perform the action. か、呼び出すことによって、オブジェクトが列挙されるまで、このメソッドによって表されるクエリは実行されません、GetEnumeratorメソッドを使用して直接またはforeachVisual C# またはFor EachVisual Basic で。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 Visual C# or For Each in Visual Basic.

メソッドDistinct<TSource>(IEnumerable<TSource>)は、重複する値を含まない順序付けられていないシーケンスを返します。The Distinct<TSource>(IEnumerable<TSource>) method returns an unordered sequence that contains no duplicate values. 既定の等値比較子Defaultを使用して、値を比較します。It uses the default equality comparer, Default, to compare values.

Visual Basic のクエリ式の構文でDistinctは、句はのDistinct呼び出しに変換します。In Visual Basic query expression syntax, a Distinct clause translates to an invocation of Distinct.

既定の等値比較Default子は、 IEquatable<T>ジェネリックインターフェイスを実装する型の値を比較するために使用されます。The default equality comparer, Default, is used to compare values of the types that implement the IEquatable<T> generic interface. カスタムデータ型を比較するには、このインターフェイスを実装し、型にGetHashCode対しEqualsて独自のメソッドとメソッドを提供する必要があります。To compare a custom data type, you need to implement this interface and provide your own GetHashCode and Equals methods for the type.

を使用IEqualityComparer<T>してカスタム比較子を定義する例にDistinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)ついては、「」を参照してください。For an example that uses IEqualityComparer<T> to define a custom comparer, see Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>).

こちらもご覧ください

Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

指定された IEqualityComparer<T> を使用して値を比較することにより、シーケンスから一意の要素を返します。Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Distinct(System::Collections::Generic::IEnumerable<TSource> ^ source, System::Collections::Generic::IEqualityComparer<TSource> ^ comparer);
public static System.Collections.Generic.IEnumerable<TSource> Distinct<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, System.Collections.Generic.IEqualityComparer<TSource> comparer);
static member Distinct : seq<'Source> * System.Collections.Generic.IEqualityComparer<'Source> -> seq<'Source>
<Extension()>
Public Function Distinct(Of TSource) (source As IEnumerable(Of TSource), comparer As IEqualityComparer(Of TSource)) As IEnumerable(Of TSource)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

重複する要素を削除する対象となるシーケンス。The sequence to remove duplicate elements from.

comparer
IEqualityComparer<TSource>

値を比較する IEqualityComparer<T>An IEqualityComparer<T> to compare values.

戻り値

IEnumerable<TSource>

ソース シーケンスの一意の要素を格納する IEnumerable<T>An IEnumerable<T> that contains distinct elements from the source sequence.

例外

次の例は、 Distinctメソッドで使用できる等値比較子を実装する方法を示しています。The following example shows how to implement an equality comparer that can be used in the Distinct 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

この比較子を実装した後、次の例Productに示すようDistinctに、メソッドでオブジェクトのシーケンスを使用できます。After you implement this comparer, you can use a sequence of Product objects in the Distinct method, as shown in the following example:

Product[] products = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 }, 
                       new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "lemon", Code = 12 } };

//Exclude duplicates.

IEnumerable<Product> noduplicates =
    products.Distinct(new ProductComparer());

foreach (var product in noduplicates)
    Console.WriteLine(product.Name + " " + product.Code);

/*
    This code produces the following output:
    apple 9 
    orange 4
    lemon 12
*/

Dim products() As Product = 
    {New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "orange", .Code = 4}, 
     New Product With {.Name = "apple", .Code = 9}, 
     New Product With {.Name = "lemon", .Code = 12}}

' Exclude duplicates.

Dim noduplicates = products.Distinct(New ProductComparer())

For Each product In noduplicates
    Console.WriteLine(product.Name & " " & product.Code)
Next

' This code produces the following output:
'
' apple 9
' orange 4
' lemon 12
' 

注釈

このメソッドは、遅延実行を使用して実装されます。This method is implemented by using deferred execution. イミディエイトの戻り値は、アクションを実行するために必要なすべての情報を格納するオブジェクトです。The immediate return value is an object that stores all the information that is required to perform the action. か、呼び出すことによって、オブジェクトが列挙されるまで、このメソッドによって表されるクエリは実行されません、GetEnumeratorメソッドを使用して直接またはforeachVisual C# またはFor EachVisual Basic で。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 Visual C# or For Each in Visual Basic.

メソッドDistinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)は、重複する値を含まない順序付けられていないシーケンスを返します。The Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>) method returns an unordered sequence that contains no duplicate values. comparer Defaultの場合、既定の等値比較子 () を使用して値を比較します。 nullIf comparer is null, the default equality comparer, Default, is used to compare values.

適用対象