Enumerable.ToDictionary Method

Definition

Overloads

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

根據指定的索引鍵選取器和項目選取器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

根據指定的索引鍵選取器函式、比較子和項目選取器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

根據指定的索引鍵選擇器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

根據指定的索引鍵選取器函式和索引鍵比較子,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

根據指定的索引鍵選取器和項目選取器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::Dictionary<TKey, TElement> ^ ToDictionary(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector);
public static System.Collections.Generic.Dictionary<TKey,TElement> ToDictionary<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector);
static member ToDictionary : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> -> System.Collections.Generic.Dictionary<'Key, 'Element>
<Extension()>
Public Function ToDictionary(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement)) As Dictionary(Of TKey, TElement)

Type Parameters

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the key returned by keySelector.

TElement

elementSelector 所傳回值的型別。The type of the value returned by elementSelector.

Parameters

source
IEnumerable<TSource>

用來建立 Dictionary<TKey,TValue> 的來源 IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

用來從每個項目產生結果項目值的轉換函式。A transform function to produce a result element value from each element.

Returns

Dictionary<TKey,TElement>

Dictionary<TKey,TValue>,包含從輸入序列選取之 TElement 類型的值。A Dictionary<TKey,TValue> that contains values of type TElement selected from the input sequence.

Exceptions

sourcekeySelectorelementSelectornullsource or keySelector or elementSelector is null.

-或--or- keySelector 產生的索引鍵為 nullkeySelector produces a key that is null.

keySelector 產生兩個項目的重複索引鍵。keySelector produces duplicate keys for two elements.

Remarks

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) 方法會使用預設的相等比較子 Default 來比較索引鍵。The ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method uses the default equality comparer Default to compare keys.

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

根據指定的索引鍵選取器函式、比較子和項目選取器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::Dictionary<TKey, TElement> ^ ToDictionary(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.Dictionary<TKey,TElement> ToDictionary<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 ToDictionary : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Collections.Generic.Dictionary<'Key, 'Element>
<Extension()>
Public Function ToDictionary(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 Dictionary(Of TKey, TElement)

Type Parameters

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the key returned by keySelector.

TElement

elementSelector 所傳回值的型別。The type of the value returned by elementSelector.

Parameters

source
IEnumerable<TSource>

用來建立 Dictionary<TKey,TValue> 的來源 IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

用來從每個項目產生結果項目值的轉換函式。A transform function to produce a result element value from each element.

comparer
IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

Returns

Dictionary<TKey,TElement>

Dictionary<TKey,TValue>,包含從輸入序列選取之 TElement 類型的值。A Dictionary<TKey,TValue> that contains values of type TElement selected from the input sequence.

Exceptions

sourcekeySelectorelementSelectornullsource or keySelector or elementSelector is null.

-或--or- keySelector 產生的索引鍵為 nullkeySelector produces a key that is null.

keySelector 產生兩個項目的重複索引鍵。keySelector produces duplicate keys for two elements.

Remarks

如果 null``comparer,則會使用預設的相等比較子 Default 來比較索引鍵。If comparer is null, the default equality comparer Default is used to compare keys.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

根據指定的索引鍵選擇器函式,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::Dictionary<TKey, TSource> ^ ToDictionary(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);
public static System.Collections.Generic.Dictionary<TKey,TSource> ToDictionary<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);
static member ToDictionary : seq<'Source> * Func<'Source, 'Key> -> System.Collections.Generic.Dictionary<'Key, 'Source>
<Extension()>
Public Function ToDictionary(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As Dictionary(Of TKey, TSource)

Type Parameters

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the key returned by keySelector.

Parameters

source
IEnumerable<TSource>

用來建立 Dictionary<TKey,TValue> 的來源 IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

Returns

Dictionary<TKey,TSource>

包含索引鍵和值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains keys and values. 每個群組中的值與 source 中的順序相同。The values within each group are in the same order as in source.

Exceptions

sourcekeySelectornullsource or keySelector is null.

-或--or- keySelector 產生的索引鍵為 nullkeySelector produces a key that is null.

keySelector 產生兩個項目的重複索引鍵。keySelector produces duplicate keys for two elements.

Examples

下列程式碼範例示範如何使用 ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>),以使用索引鍵選取器來建立 Dictionary<TKey,TValue>The following code example demonstrates how to use ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) to create a Dictionary<TKey,TValue> by using a key selector.

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

public static void ToDictionaryEx1()
{
    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 = "Adventure Works", Weight = 33.8, TrackingNumber = 4665518773L } };

    // Create a Dictionary of Package objects,
    // using TrackingNumber as the key.
    Dictionary<long, Package> dictionary =
        packages.ToDictionary(p => p.TrackingNumber);

    foreach (KeyValuePair<long, Package> kvp in dictionary)
    {
        Console.WriteLine(
            "Key {0}: {1}, {2} pounds",
            kvp.Key,
            kvp.Value.Company,
            kvp.Value.Weight);
    }
}

/*
 This code produces the following output:

 Key 89453312: Coho Vineyard, 25.2 pounds
 Key 89112755: Lucerne Publishing, 18.7 pounds
 Key 299456122: Wingtip Toys, 6 pounds
 Key 4665518773: Adventure Works, 33.8 pounds
*/
Structure Package
    Public Company As String
    Public Weight As Double
    Public TrackingNumber As Long
End Structure

Sub ToDictionaryEx1()
    ' Create a list of Package values.
    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 = "Adventure Works", .Weight = 33.8, .TrackingNumber = 4665518773L}})

    ' Create a Dictionary that contains Package values, 
    ' using TrackingNumber as the key.
    Dim dict As Dictionary(Of Long, Package) =
    packages.ToDictionary(Function(p) p.TrackingNumber)

    ' Display the results.
    Dim output As New System.Text.StringBuilder
    For Each kvp As KeyValuePair(Of Long, Package) In dict
        output.AppendLine("Key " & kvp.Key & ": " &
                      kvp.Value.Company & ", " &
                      kvp.Value.Weight & " pounds")
    Next
    Console.WriteLine(output.ToString())
End Sub

' This code produces the following output:
'
' Key 89453312: Coho Vineyard, 25.2 pounds
' Key 89112755: Lucerne Publishing, 18.7 pounds
' Key 299456122: Wingtip Toys, 6 pounds
' Key 4665518773: Adventure Works, 33.8 pounds

Remarks

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) 方法會使用預設的相等比較子 Default 來比較索引鍵。The ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method uses the default equality comparer Default to compare keys.

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

根據指定的索引鍵選取器函式和索引鍵比較子,從 Dictionary<TKey,TValue> 建立 IEnumerable<T>Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.

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

Type Parameters

TSource

source 項目的類型。The type of the elements of source.

TKey

keySelector 所傳回之索引鍵的型別。The type of the keys returned by keySelector.

Parameters

source
IEnumerable<TSource>

用來建立 Dictionary<TKey,TValue> 的來源 IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用來從各個項目擷取索引鍵的函式。A function to extract a key from each element.

comparer
IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

Returns

Dictionary<TKey,TSource>

包含索引鍵和值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains keys and values. 每個群組中的值與 source 中的順序相同。The values within each group are in the same order as in source.

Exceptions

sourcekeySelectornullsource or keySelector is null.

-或--or- keySelector 產生的索引鍵為 nullkeySelector produces a key that is null.

keySelector 產生兩個項目的重複索引鍵。keySelector produces duplicate keys for two elements.

Remarks

如果 null``comparer,則會使用預設的相等比較子 Default 來比較索引鍵。If comparer is null, the default equality comparer Default is used to compare keys.

Applies to