Enumerable.ToDictionary 方法

定义

重载

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

根据指定的键选择器和元素选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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>)

根据指定的键选择器函数、比较器和元素选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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>)

根据指定的键选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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>)

根据指定的键选择器函数和键比较器,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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>)

根据指定的键选择器和元素选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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)

类型参数

TSource

source 的元素类型。The type of the elements of source.

TKey

keySelector 返回的键的类型。The type of the key returned by keySelector.

TElement

elementSelector 返回的值的类型。The type of the value returned by elementSelector.

参数

source
IEnumerable<TSource>

要从其创建 Dictionary<TKey,TValue>IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用于从每个元素中提取键的函数。A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

用于从每个元素产生结果元素值的转换函数。A transform function to produce a result element value from each element.

返回

Dictionary<TKey,TElement>

一个包含从输入序列中选择的类型为 TElement 的值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains values of type TElement selected from the input sequence.

例外

sourcekeySelectorelementSelectornullsource or keySelector or elementSelector is null.

- 或 --or- keySelector 生成一个 null 的键。keySelector produces a key that is null.

keySelector 为两个元素生成重复键。keySelector produces duplicate keys for two elements.

注解

ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)方法使用默认的相等比较器 Default 对键进行比较。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>)

根据指定的键选择器函数、比较器和元素选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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);
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)

类型参数

TSource

source 的元素类型。The type of the elements of source.

TKey

keySelector 返回的键的类型。The type of the key returned by keySelector.

TElement

elementSelector 返回的值的类型。The type of the value returned by elementSelector.

参数

source
IEnumerable<TSource>

要从其创建 Dictionary<TKey,TValue>IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用于从每个元素中提取键的函数。A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

用于从每个元素产生结果元素值的转换函数。A transform function to produce a result element value from each element.

comparer
IEqualityComparer<TKey>

用于比较键的 IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

返回

Dictionary<TKey,TElement>

一个包含从输入序列中选择的类型为 TElement 的值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains values of type TElement selected from the input sequence.

例外

sourcekeySelectorelementSelectornullsource or keySelector or elementSelector is null.

- 或 --or- keySelector 生成一个 null 的键。keySelector produces a key that is null.

keySelector 为两个元素生成重复键。keySelector produces duplicate keys for two elements.

注解

如果 comparernull ,则使用默认的相等比较器 Default 对键进行比较。If comparer is null, the default equality comparer Default is used to compare keys.

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

根据指定的键选择器函数,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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)

类型参数

TSource

source 的元素类型。The type of the elements of source.

TKey

keySelector 返回的键的类型。The type of the key returned by keySelector.

参数

source
IEnumerable<TSource>

要从其创建 Dictionary<TKey,TValue>IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用于从每个元素中提取键的函数。A function to extract a key from each element.

返回

Dictionary<TKey,TSource>

一个包含键和值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains keys and values. 每个组中的值顺序与 source 中的顺序相同。The values within each group are in the same order as in source.

例外

sourcekeySelectornullsource or keySelector is null.

- 或 --or- keySelector 生成一个 null 的键。keySelector produces a key that is null.

keySelector 为两个元素生成重复键。keySelector produces duplicate keys for two elements.

示例

下面的代码示例演示如何使用 ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) Dictionary<TKey,TValue> 通过键选择器创建。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

注解

ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)方法使用默认的相等比较器 Default 对键进行比较。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>)

根据指定的键选择器函数和键比较器,从 IEnumerable<T> 创建一个 Dictionary<TKey,TValue>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);
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)

类型参数

TSource

source 的元素类型。The type of the elements of source.

TKey

keySelector 返回的键的类型。The type of the keys returned by keySelector.

参数

source
IEnumerable<TSource>

要从其创建 Dictionary<TKey,TValue>IEnumerable<T>An IEnumerable<T> to create a Dictionary<TKey,TValue> from.

keySelector
Func<TSource,TKey>

用于从每个元素中提取键的函数。A function to extract a key from each element.

comparer
IEqualityComparer<TKey>

用于比较键的 IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

返回

Dictionary<TKey,TSource>

一个包含键和值的 Dictionary<TKey,TValue>A Dictionary<TKey,TValue> that contains keys and values. 每个组中的值顺序与 source 中的顺序相同。The values within each group are in the same order as in source.

例外

sourcekeySelectornullsource or keySelector is null.

- 或 --or- keySelector 生成一个 null 的键。keySelector produces a key that is null.

keySelector 为两个元素生成重复键。keySelector produces duplicate keys for two elements.

注解

如果 comparernull ,则使用默认的相等比较器 Default 对键进行比较。If comparer is null, the default equality comparer Default is used to compare keys.

适用于