Enumerable.ToLookup Methode

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::ILookup<TKey, TElement> ^ ToLookup(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector);

public static System.Linq.ILookup<TKey,TElement> ToLookup<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector);

static member ToLookup : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> -> System.Linq.ILookup<'Key, 'Element>

<Extension()>
Public Function ToLookup(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement)) As ILookup(Of TKey, TElement)

Typparameter

Parameter

Gibt zurück

ILookup<TKey,TElement>

Ein Lookup<TKey,TElement>, das Werte vom Typ TElement enthält, die aus der Eingabesequenz ausgewählt werden.A Lookup<TKey,TElement> that contains values of type TElement selected from the input sequence.

Ausnahmen

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) Lookup<TKey,TElement> mithilfe von eine Schlüsselauswahl Funktion und eine Elementauswahl Funktion erstellt werden.The following code example demonstrates how to use ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) to create a Lookup<TKey,TElement> by using a key selector function and an element selector function.

class Package
{
    public string Company { get; set; }
    public double Weight { get; set; }
    public long TrackingNumber { get; set; }
}

public static void ToLookupEx1()
{
    // Create a list of Packages.
    List<Package> packages =
        new List<Package>
            { new Package { Company = "Coho Vineyard",
                  Weight = 25.2, TrackingNumber = 89453312L },
              new Package { Company = "Lucerne Publishing",
                  Weight = 18.7, TrackingNumber = 89112755L },
              new Package { Company = "Wingtip Toys",
                  Weight = 6.0, TrackingNumber = 299456122L },
              new Package { Company = "Contoso Pharmaceuticals",
                  Weight = 9.3, TrackingNumber = 670053128L },
              new Package { Company = "Wide World Importers",
                  Weight = 33.8, TrackingNumber = 4665518773L } };

    // Create a Lookup to organize the packages.
    // Use the first character of Company as the key value.
    // Select Company appended to TrackingNumber
    // as the element values of the Lookup.
    ILookup<char, string> lookup =
        packages
        .ToLookup(p => Convert.ToChar(p.Company.Substring(0, 1)),
                  p => p.Company + " " + p.TrackingNumber);

    // Iterate through each IGrouping in the Lookup.
    foreach (IGrouping<char, string> packageGroup in lookup)
    {
        // Print the key value of the IGrouping.
        Console.WriteLine(packageGroup.Key);
        // Iterate through each value in the
        // IGrouping and print its value.
        foreach (string str in packageGroup)
            Console.WriteLine("    {0}", str);
    }
}

/*
 This code produces the following output:

 C
     Coho Vineyard 89453312
     Contoso Pharmaceuticals 670053128
 L
     Lucerne Publishing 89112755
 W
     Wingtip Toys 299456122
     Wide World Importers 4665518773
*/

Structure Package
    Public Company As String
    Public Weight As Double
    Public TrackingNumber As Long
End Structure

Sub ToLookupEx1()
    ' Create a list of Packages.
    Dim packages As New List(Of Package)(New Package() _
     {New Package With
      {.Company = "Coho Vineyard", .Weight = 25.2, .TrackingNumber = 89453312L},
      New Package With
      {.Company = "Lucerne Publishing", .Weight = 18.7, .TrackingNumber = 89112755L},
      New Package With
      {.Company = "Wingtip Toys", .Weight = 6.0, .TrackingNumber = 299456122L},
      New Package With
      {.Company = "Contoso Pharmaceuticals", .Weight = 9.3, .TrackingNumber = 670053128L},
      New Package With
      {.Company = "Wide World Importers", .Weight = 33.8, .TrackingNumber = 4665518773L}})

    ' Create a Lookup to organize the packages. 
    ' Use the first character of Company as the key value.
    ' Select Company appended to TrackingNumber 
    ' as the element values of the Lookup.
    Dim lookup As ILookup(Of Char, String) =
    packages.ToLookup(Function(p) _
                          Convert.ToChar(p.Company.Substring(0, 1)),
                      Function(p) _
                          p.Company & " " & p.TrackingNumber)

    Dim output As New System.Text.StringBuilder

    ' Iterate through each IGrouping in the Lookup.
    For Each packageGroup As IGrouping(Of Char, String) In lookup
        ' Print the key value of the IGrouping.
        output.AppendLine(packageGroup.Key)
        ' Iterate through each value in the IGrouping and print its value.
        For Each str As String In packageGroup
            output.AppendLine("   " & str)
        Next
    Next

    ' Select a group of packages by indexing directly into the Lookup.
    Dim cgroup As IEnumerable(Of String) = lookup("C"c)

    output.AppendLine(vbCrLf & "Packages from Company names that start with 'C':")
    For Each str As String In cgroup
        output.AppendLine(str)
    Next

    ' Display the output.
    Console.WriteLine(output.ToString())
End Sub

' This code produces the following output:
'
' C
'    Coho Vineyard 89453312
'    Contoso Pharmaceuticals 670053128
' L
'    Lucerne Publishing 89112755
' W
'    Wingtip Toys 299456122
'    Wide World Importers 4665518773
'
' Packages from Company names that start with 'C':
' Coho Vineyard 89453312
' Contoso Pharmaceuticals 670053128

Hinweise

Die- ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) Methode gibt einen zurück Lookup<TKey,TElement> , ein 1: n-Wörterbuch, das Schlüssel Auflistungen von Werten zuordnet.The ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Ein unter Lookup<TKey,TElement> scheidet sich von einem Dictionary<TKey,TValue> , das eine eins-zu-Eins-Zuordnung von Schlüsseln zu einzelnen Werten ausführt.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

Der Standard Gleichheits Vergleich Default wird zum Vergleichen von Schlüsseln verwendet.The default equality comparer Default is used to compare keys.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::ILookup<TKey, TElement> ^ ToLookup(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);

public static System.Linq.ILookup<TKey,TElement> ToLookup<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);

public static System.Linq.ILookup<TKey,TElement> ToLookup<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);

static member ToLookup : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.ILookup<'Key, 'Element>

<Extension()>
Public Function ToLookup(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), comparer As IEqualityComparer(Of TKey)) As ILookup(Of TKey, TElement)

Typparameter

Parameter

Gibt zurück

ILookup<TKey,TElement>

Ein Lookup<TKey,TElement>, das Werte vom Typ TElement enthält, die aus der Eingabesequenz ausgewählt werden.A Lookup<TKey,TElement> that contains values of type TElement selected from the input sequence.

Ausnahmen

Hinweise

Die- ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) Methode gibt einen zurück Lookup<TKey,TElement> , ein 1: n-Wörterbuch, das Schlüssel Auflistungen von Werten zuordnet.The ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Ein unter Lookup<TKey,TElement> scheidet sich von einem Dictionary<TKey,TValue> , das eine eins-zu-Eins-Zuordnung von Schlüsseln zu einzelnen Werten ausführt.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

Wenn comparer null den Wert hat, wird der Standard Gleichheits Vergleich Default verwendet, um Schlüssel zu vergleichen.If comparer is null, the default equality comparer Default is used to compare keys.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::ILookup<TKey, TSource> ^ ToLookup(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);

public static System.Linq.ILookup<TKey,TSource> ToLookup<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);

static member ToLookup : seq<'Source> * Func<'Source, 'Key> -> System.Linq.ILookup<'Key, 'Source>

<Extension()>
Public Function ToLookup(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As ILookup(Of TKey, TSource)

Typparameter

Parameter

Gibt zurück

ILookup<TKey,TSource>

Ein Lookup<TKey,TElement>, das Schlüssel und Werte enthält.A Lookup<TKey,TElement> that contains keys and values. Die Werte in den einzelnen Gruppen liegen in der gleichen Reihenfolge vor wie in source.The values within each group are in the same order as in source.

Ausnahmen

Hinweise

Die- ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) Methode gibt einen zurück Lookup<TKey,TElement> , ein 1: n-Wörterbuch, das Schlüssel Auflistungen von Werten zuordnet.The ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Ein unter Lookup<TKey,TElement> scheidet sich von einem Dictionary<TKey,TValue> , das eine eins-zu-Eins-Zuordnung von Schlüsseln zu einzelnen Werten ausführt.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

Der Standard Gleichheits Vergleich Default wird zum Vergleichen von Schlüsseln verwendet.The default equality comparer Default is used to compare keys.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::ILookup<TKey, TSource> ^ ToLookup(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);

public static System.Linq.ILookup<TKey,TSource> ToLookup<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);

public static System.Linq.ILookup<TKey,TSource> ToLookup<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);

static member ToLookup : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.ILookup<'Key, 'Source>

<Extension()>
Public Function ToLookup(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), comparer As IEqualityComparer(Of TKey)) As ILookup(Of TKey, TSource)

Typparameter

Parameter

Gibt zurück

ILookup<TKey,TSource>

Ein Lookup<TKey,TElement>, das Schlüssel und Werte enthält.A Lookup<TKey,TElement> that contains keys and values. Die Werte in den einzelnen Gruppen liegen in der gleichen Reihenfolge vor wie in source.The values within each group are in the same order as in source.

Ausnahmen

Hinweise

Die- ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) Methode gibt einen zurück Lookup<TKey,TElement> , ein 1: n-Wörterbuch, das Schlüssel Auflistungen von Werten zuordnet.The ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Ein Lookup<TKey,TElement> unterscheidet sich von einem Dictionary<TKey,TValue> , das eine eins-zu-Eins-Zuordnung von Schlüsseln zu einzelnen Werten ausführt.A Lookup<TKey,TElement> is different to a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

Wenn comparer null den Wert hat, wird der Standard Gleichheits Vergleich Default verwendet, um Schlüssel zu vergleichen.If comparer is null, the default equality comparer Default is used to compare keys.