ConcurrentDictionary<TKey,TValue> Class

Definition

Namespace:

System.Collections.Concurrent

Assembly:

System.Collections.Concurrent.dll

Source:

ConcurrentDictionary.cs

Represents a thread-safe collection of key/value pairs that can be accessed by multiple threads concurrently.

generic <typename TKey, typename TValue>
public ref class ConcurrentDictionary : System::Collections::Generic::ICollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IDictionary<TKey, TValue>, System::Collections::Generic::IEnumerable<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyCollection<System::Collections::Generic::KeyValuePair<TKey, TValue>>, System::Collections::Generic::IReadOnlyDictionary<TKey, TValue>, System::Collections::IDictionary

public class ConcurrentDictionary<TKey,TValue> : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IDictionary<TKey,TValue>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, System.Collections.IDictionary

type ConcurrentDictionary<'Key, 'Value> = class
    interface ICollection<KeyValuePair<'Key, 'Value>>
    interface seq<KeyValuePair<'Key, 'Value>>
    interface IEnumerable
    interface IDictionary<'Key, 'Value>
    interface IReadOnlyCollection<KeyValuePair<'Key, 'Value>>
    interface IReadOnlyDictionary<'Key, 'Value>
    interface ICollection
    interface IDictionary

Public Class ConcurrentDictionary(Of TKey, TValue)
Implements ICollection(Of KeyValuePair(Of TKey, TValue)), IDictionary, IDictionary(Of TKey, TValue), IEnumerable(Of KeyValuePair(Of TKey, TValue)), IReadOnlyCollection(Of KeyValuePair(Of TKey, TValue)), IReadOnlyDictionary(Of TKey, TValue)

Type Parameters

TKey

The type of the keys in the dictionary.

TValue

The type of the values in the dictionary.

Inheritance

Object

ConcurrentDictionary<TKey,TValue>

Implements

ICollection<KeyValuePair<TKey,TValue>> IDictionary<TKey,TValue> IEnumerable<KeyValuePair<TKey,TValue>> IEnumerable<T> IReadOnlyCollection<KeyValuePair<TKey,TValue>> IReadOnlyDictionary<TKey,TValue> ICollection IDictionary IEnumerable

Examples

The following example shows how to construct a ConcurrentDictionary<TKey,TValue> object.

class CD_Ctor
{
        // Demonstrates:
        //      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
        //      ConcurrentDictionary<TKey, TValue>[TKey]
        static void Main()
        {
            // We know how many items we want to insert into the ConcurrentDictionary.
            // So set the initial capacity to some prime number above that, to ensure that
            // the ConcurrentDictionary does not need to be resized while initializing it.
            int NUMITEMS = 64;
            int initialCapacity = 101;

            // The higher the concurrencyLevel, the higher the theoretical number of operations
            // that could be performed concurrently on the ConcurrentDictionary.  However, global
            // operations like resizing the dictionary take longer as the concurrencyLevel rises.
            // For the purposes of this example, we'll compromise at numCores * 2.
            int numProcs = Environment.ProcessorCount;
            int concurrencyLevel = numProcs * 2;

            // Construct the dictionary with the desired concurrencyLevel and initialCapacity
            ConcurrentDictionary<int, int> cd = new ConcurrentDictionary<int, int>(concurrencyLevel, initialCapacity);

            // Initialize the dictionary
            for (int i = 0; i < NUMITEMS; i++) cd[i] = i * i;

            Console.WriteLine("The square of 23 is {0} (should be {1})", cd[23], 23 * 23);
        }
}

// Demonstrates:
//      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
//      ConcurrentDictionary<TKey, TValue>[TKey]

// We know how many items we want to insert into the ConcurrentDictionary.
// So set the initial capacity to some prime number above that, to ensure that
// the ConcurrentDictionary does not need to be resized while initializing it.
let NUMITEMS = 64
let initialCapacity = 101

// The higher the concurrencyLevel, the higher the theoretical number of operations
// that could be performed concurrently on the ConcurrentDictionary.  However, global
// operations like resizing the dictionary take longer as the concurrencyLevel rises.
// For the purposes of this example, we'll compromise at numCores * 2.
let numProcs = Environment.ProcessorCount
let concurrencyLevel = numProcs * 2

// Construct the dictionary with the desired concurrencyLevel and initialCapacity
let cd = ConcurrentDictionary<int, int>(concurrencyLevel, initialCapacity)

// Initialize the dictionary
for i = 0 to NUMITEMS - 1 do
    cd[i] <- i * i

printfn $"The square of 23 is {cd[23]} (should be {23 * 23})"

Imports System.Collections.Concurrent
Imports System.Threading.Tasks

Class CD_Ctor
    ' Demonstrates:
    ' ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
    ' ConcurrentDictionary<TKey, TValue>[TKey]
    Shared Sub Main()
        ' We know how many items we want to insert into the ConcurrentDictionary.
        ' So set the initial capacity to some prime number above that, to ensure that
        ' the ConcurrentDictionary does not need to be resized while initializing it.
        Dim NUMITEMS As Integer = 64
        Dim initialCapacity As Integer = 101

        ' The higher the concurrencyLevel, the higher the theoretical number of operations
        ' that could be performed concurrently on the ConcurrentDictionary. However, global
        ' operations like resizing the dictionary take longer as the concurrencyLevel rises. 
        ' For the purposes of this example, we'll compromise at numCores * 2.
        Dim numProcs As Integer = Environment.ProcessorCount
        Dim concurrencyLevel As Integer = numProcs * 2

        ' Construct the dictionary with the desired concurrencyLevel and initialCapacity
        Dim cd As New ConcurrentDictionary(Of Integer, Integer)(concurrencyLevel, initialCapacity)

        ' Initialize the dictionary
        For i As Integer = 0 To NUMITEMS - 1
            cd(i) = i * i
        Next

        Console.WriteLine("The square of 23 is {0} (should be {1})", cd(23), 23 * 23)
    End Sub
End Class

Remarks

For very large ConcurrentDictionary<TKey,TValue> objects, you can increase the maximum array size to 2 gigabytes (GB) on a 64-bit system by setting the <gcAllowVeryLargeObjects> configuration element to true in the run-time environment.

Note

ConcurrentDictionary<TKey,TValue> implements the IReadOnlyCollection<T> and IReadOnlyDictionary<TKey,TValue> interfaces starting with the .NET Framework 4.6; in previous versions of the .NET Framework, the ConcurrentDictionary<TKey,TValue> class did not implement these interfaces.

Like the System.Collections.Generic.Dictionary<TKey,TValue> class, ConcurrentDictionary<TKey,TValue> implements the IDictionary<TKey,TValue> interface. In addition, ConcurrentDictionary<TKey,TValue> provides several methods for adding or updating key/value pairs in the dictionary, as described in the following table.

To do this	Use this method	Usage notes
Add a new key to the dictionary, if it doesn't already exist in the dictionary	TryAdd	This method adds the specified key/value pair, if the key doesn't currently exist in the dictionary. The method returns true or false depending on whether the new pair was added.
Update the value for an existing key in the dictionary, if that key has a specific value	TryUpdate	This method checks whether the key has a specified value, and if it does, updates the key with a new value. It's similar to the CompareExchange method, except that it's used for dictionary elements.
Store a key/value pair in the dictionary unconditionally, and overwrite the value of a key that already exists	The indexer's setter: dictionary[key] = newValue
Add a key/value pair to the dictionary, or if the key already exists, update the value for the key based on the key's existing value	AddOrUpdate(TKey, Func<TKey,TValue>, Func<TKey,TValue,TValue>) -or- AddOrUpdate(TKey, TValue, Func<TKey,TValue,TValue>)	AddOrUpdate(TKey, Func<TKey,TValue>, Func<TKey,TValue,TValue>) accepts the key and two delegates. It uses the first delegate if the key doesn't exist in the dictionary; it accepts the key and returns the value that should be added for the key. It uses the second delegate if the key does exist; it accepts the key and its current value, and it returns the new value that should be set for the key. AddOrUpdate(TKey, TValue, Func<TKey,TValue,TValue>) accepts the key, a value to add, and the update delegate. This is the same as the previous overload, except that it doesn't use a delegate to add a key.
Get the value for a key in the dictionary, adding the value to the dictionary and returning it if the key doesn't exist	GetOrAdd(TKey, TValue) -or- GetOrAdd(TKey, Func<TKey,TValue>)	These overloads provide lazy initialization for a key/value pair in the dictionary, adding the value only if it's not there. GetOrAdd(TKey, TValue) takes the value to be added if the key doesn't exist. GetOrAdd(TKey, Func<TKey,TValue>) takes a delegate that will generate the value if the key doesn't exist.

All these operations are atomic and are thread-safe with regards to all other operations on the ConcurrentDictionary<TKey,TValue> class. The only exceptions are the methods that accept a delegate, that is, AddOrUpdate and GetOrAdd. For modifications and write operations to the dictionary, ConcurrentDictionary<TKey,TValue> uses fine-grained locking to ensure thread safety. (Read operations on the dictionary are performed in a lock-free manner.) However, delegates for these methods are called outside the locks to avoid the problems that can arise from executing unknown code under a lock. Therefore, the code executed by these delegates is not subject to the atomicity of the operation.

Constructors

ConcurrentDictionary<TKey,TValue>()	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that is empty, has the default concurrency level, has the default initial capacity, and uses the default comparer for the key type.
ConcurrentDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that contains elements copied from the specified IEnumerable<T>, has the default concurrency level, has the default initial capacity, and uses the default comparer for the key type.
ConcurrentDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that contains elements copied from the specified IEnumerable has the default concurrency level, has the default initial capacity, and uses the specified IEqualityComparer<T>.
ConcurrentDictionary<TKey,TValue>(IEqualityComparer<TKey>)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that is empty, has the default concurrency level and capacity, and uses the specified IEqualityComparer<T>.
ConcurrentDictionary<TKey,TValue>(Int32, IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that contains elements copied from the specified IEnumerable, and uses the specified IEqualityComparer<T>.
ConcurrentDictionary<TKey,TValue>(Int32, Int32)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that is empty, has the specified concurrency level and capacity, and uses the default comparer for the key type.
ConcurrentDictionary<TKey,TValue>(Int32, Int32, IEqualityComparer<TKey>)	Initializes a new instance of the ConcurrentDictionary<TKey,TValue> class that is empty, has the specified concurrency level, has the specified initial capacity, and uses the specified IEqualityComparer<T>.

Properties

Comparer	Gets the IEqualityComparer<T> that is used to determine equality of keys for the dictionary.
Count	Gets the number of key/value pairs contained in the ConcurrentDictionary<TKey,TValue>.
IsEmpty	Gets a value that indicates whether the ConcurrentDictionary<TKey,TValue> is empty.
Item[TKey]	Gets or sets the value associated with the specified key.
Keys	Gets a collection containing the keys in the Dictionary<TKey,TValue>.
Values	Gets a collection that contains the values in the Dictionary<TKey,TValue>.

Methods

AddOrUpdate(TKey, Func<TKey,TValue>, Func<TKey,TValue,TValue>)	Uses the specified functions to add a key/value pair to the ConcurrentDictionary<TKey,TValue> if the key does not already exist, or to update a key/value pair in the ConcurrentDictionary<TKey,TValue> if the key already exists.
AddOrUpdate(TKey, TValue, Func<TKey,TValue,TValue>)	Adds a key/value pair to the ConcurrentDictionary<TKey,TValue> if the key does not already exist, or updates a key/value pair in the ConcurrentDictionary<TKey,TValue> by using the specified function if the key already exists.
AddOrUpdate<TArg>(TKey, Func<TKey,TArg,TValue>, Func<TKey,TValue,TArg,TValue>, TArg)	Uses the specified functions and argument to add a key/value pair to the ConcurrentDictionary<TKey,TValue> if the key does not already exist, or to update a key/value pair in the ConcurrentDictionary<TKey,TValue> if the key already exists.
Clear()	Removes all keys and values from the ConcurrentDictionary<TKey,TValue>.
ContainsKey(TKey)	Determines whether the ConcurrentDictionary<TKey,TValue> contains the specified key.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetEnumerator()	Returns an enumerator that iterates through the ConcurrentDictionary<TKey,TValue>.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetOrAdd(TKey, Func<TKey,TValue>)	Adds a key/value pair to the ConcurrentDictionary<TKey,TValue> by using the specified function if the key does not already exist. Returns the new value, or the existing value if the key exists.
GetOrAdd(TKey, TValue)	Adds a key/value pair to the ConcurrentDictionary<TKey,TValue> if the key does not already exist. Returns the new value, or the existing value if the key exists.
GetOrAdd<TArg>(TKey, Func<TKey,TArg,TValue>, TArg)	Adds a key/value pair to the ConcurrentDictionary<TKey,TValue> by using the specified function and an argument if the key does not already exist, or returns the existing value if the key exists.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToArray()	Copies the key and value pairs stored in the ConcurrentDictionary<TKey,TValue> to a new array.
ToString()	Returns a string that represents the current object. (Inherited from Object)
TryAdd(TKey, TValue)	Attempts to add the specified key and value to the ConcurrentDictionary<TKey,TValue>.
TryGetValue(TKey, TValue)	Attempts to get the value associated with the specified key from the ConcurrentDictionary<TKey,TValue>.
TryRemove(KeyValuePair<TKey,TValue>)	Removes a key and value from the dictionary.
TryRemove(TKey, TValue)	Attempts to remove and return the value that has the specified key from the ConcurrentDictionary<TKey,TValue>.
TryUpdate(TKey, TValue, TValue)	Updates the value associated with key to newValue if the existing value with key is equal to comparisonValue.

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32)	Copies the elements of the ICollection to an array, starting at the specified array index.
ICollection.IsSynchronized	Gets a value that indicates whether access to the ICollection is synchronized with the SyncRoot.
ICollection.SyncRoot	Gets an object that can be used to synchronize access to the ICollection. This property is not supported.
ICollection<KeyValuePair<TKey,TValue>>.Add(KeyValuePair<TKey,TValue>)	Adds an item to the collection.
ICollection<KeyValuePair<TKey,TValue>>.Contains(KeyValuePair<TKey,TValue>)	Gets whether the ICollection<T> contains an element with the specified key.
ICollection<KeyValuePair<TKey,TValue>>.CopyTo(KeyValuePair<TKey,TValue>[], Int32)	Copies the elements of the ICollection to an array, starting at the specified array index.
ICollection<KeyValuePair<TKey,TValue>>.IsReadOnly	Gets a value that indicates whether the ICollection is read-only.
ICollection<KeyValuePair<TKey,TValue>>.Remove(KeyValuePair<TKey,TValue>)	Removes the specified key/value pair from the collection.
IDictionary.Add(Object, Object)	Adds the specified key and value to the dictionary.
IDictionary.Contains(Object)	Gets a value that indicates the IDictionary<TKey,TValue> contains an element with the specified key.
IDictionary.GetEnumerator()	Provides a IDictionaryEnumerator for the IDictionary<TKey,TValue>.
IDictionary.IsFixedSize	Gets a value that indicates whether the IDictionary<TKey,TValue> has a fixed size.
IDictionary.IsReadOnly	Gets a value that indicates whether the IDictionary<TKey,TValue> is read-only.
IDictionary.Item[Object]	Gets or sets the value associated with the specified key.
IDictionary.Keys	Gets an ICollection that contains the keys of the IDictionary<TKey,TValue>.
IDictionary.Remove(Object)	Removes the element with the specified key from the IDictionary.
IDictionary.Values	Gets an ICollection that contains the values in the IDictionary.
IDictionary<TKey,TValue>.Add(TKey, TValue)	Adds the specified key and value to the IDictionary<TKey,TValue>.
IDictionary<TKey,TValue>.Remove(TKey)	Removes the element with the specified key from the IDictionary<TKey,TValue>.
IEnumerable.GetEnumerator()	Returns an enumerator that iterates through the ConcurrentDictionary<TKey,TValue>.
IReadOnlyDictionary<TKey,TValue>.Keys	Gets a collection containing the keys in the Dictionary<TKey,TValue>.
IReadOnlyDictionary<TKey,TValue>.Values	Gets a collection that contains the values in the Dictionary<TKey,TValue>.

Extension Methods

ToFrozenDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector function.
ToFrozenDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.
ToFrozenSet<T>(IEnumerable<T>, IEqualityComparer<T>)	Creates a FrozenSet<T> with the specified values.
AsReadOnly<TKey,TValue>(IDictionary<TKey,TValue>)	Returns a read-only ReadOnlyDictionary<TKey,TValue> wrapper for the current dictionary.
GetValueOrDefault<TKey,TValue>(IReadOnlyDictionary<TKey,TValue>, TKey)	Tries to get the value associated with the specified key in the dictionary.
GetValueOrDefault<TKey,TValue>(IReadOnlyDictionary<TKey,TValue>, TKey, TValue)	Tries to get the value associated with the specified key in the dictionary.
Remove<TKey,TValue>(IDictionary<TKey,TValue>, TKey, TValue)	Tries to remove the value with the specified key from the dictionary.
TryAdd<TKey,TValue>(IDictionary<TKey,TValue>, TKey, TValue)	Tries to add the specified key and value to the dictionary.
ToImmutableArray<TSource>(IEnumerable<TSource>)	Creates an immutable array from the specified collection.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Constructs an immutable dictionary from an existing collection of elements, applying a transformation function to the source keys.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Constructs an immutable dictionary based on some transformation of a sequence.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key comparer.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key and value comparers.
ToImmutableHashSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable hash set of its contents.
ToImmutableHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Enumerates a sequence, produces an immutable hash set of its contents, and uses the specified equality comparer for the set type.
ToImmutableList<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable list of its contents.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key comparer.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key and value comparers.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable sorted set of its contents.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Enumerates a sequence, produces an immutable sorted set of its contents, and uses the specified comparer.
CopyToDataTable<T>(IEnumerable<T>)	Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.
Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)	Applies an accumulator function over a sequence.
Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether all elements of a sequence satisfy a condition.
Any<TSource>(IEnumerable<TSource>)	Determines whether a sequence contains any elements.
Any<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether any element of a sequence satisfies a condition.
Append<TSource>(IEnumerable<TSource>, TSource)	Appends a value to the end of the sequence.
AsEnumerable<TSource>(IEnumerable<TSource>)	Returns the input typed as IEnumerable<T>.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Cast<TResult>(IEnumerable)	Casts the elements of an IEnumerable to the specified type.
Chunk<TSource>(IEnumerable<TSource>, Int32)	Splits the elements of a sequence into chunks of size at most size.
Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Concatenates two sequences.
Contains<TSource>(IEnumerable<TSource>, TSource)	Determines whether a sequence contains a specified element by using the default equality comparer.
Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)	Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.
Count<TSource>(IEnumerable<TSource>)	Returns the number of elements in a sequence.
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns a number that represents how many elements in the specified sequence satisfy a condition.
DefaultIfEmpty<TSource>(IEnumerable<TSource>)	Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.
DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)	Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.
Distinct<TSource>(IEnumerable<TSource>)	Returns distinct elements from a sequence by using the default equality comparer to compare values.
Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns distinct elements from a sequence according to a specified key selector function.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Returns distinct elements from a sequence according to a specified key selector function and using a specified comparer to compare keys.
ElementAt<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence.
ElementAt<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set difference of two sequences by using the default equality comparer to compare values.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set difference of two sequences according to a specified key selector function.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set difference of two sequences according to a specified key selector function.
First<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence.
First<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element in a sequence that satisfies a specified condition.
FirstOrDefault<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence, or a default value if the sequence contains no elements.
FirstOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the first element of a sequence, or a specified default value if the sequence contains no elements.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the first element of the sequence that satisfies a condition, or a specified default value if no such element is found.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Groups the elements of a sequence according to a specified key selector function.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource, TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>)	Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys.
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.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)	Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys.
Last<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence.
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a specified condition.
LastOrDefault<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence, or a default value if the sequence contains no elements.
LastOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the last element of a sequence, or a specified default value if the sequence contains no elements.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the last element of a sequence that satisfies a condition, or a specified default value if no such element is found.
LongCount<TSource>(IEnumerable<TSource>)	Returns an Int64 that represents the total number of elements in a sequence.
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns an Int64 that represents how many elements in a sequence satisfy a condition.
Max<TSource>(IEnumerable<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the maximum Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the maximum Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the maximum Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the maximum Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the maximum Single value.
Max<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function and key comparer.
Min<TSource>(IEnumerable<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the minimum Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the minimum Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the minimum Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the minimum Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the minimum Single value.
Min<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function and key comparer.
OfType<TResult>(IEnumerable)	Filters the elements of an IEnumerable based on a specified type.
Order<T>(IEnumerable<T>)	Sorts the elements of a sequence in ascending order.
Order<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in ascending order.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in ascending order according to a key.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in ascending order by using a specified comparer.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in descending order according to a key.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in descending order by using a specified comparer.
OrderDescending<T>(IEnumerable<T>)	Sorts the elements of a sequence in descending order.
OrderDescending<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in descending order.
Prepend<TSource>(IEnumerable<TSource>, TSource)	Adds a value to the beginning of the sequence.
Reverse<TSource>(IEnumerable<TSource>)	Inverts the order of the elements in a sequence.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Projects each element of a sequence into a new form.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>)	Projects each element of a sequence into a new form by incorporating the element's index.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.
Single<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.
SingleOrDefault<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the only element of a sequence, or a specified default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the only element of a sequence that satisfies a specified condition, or a specified default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
Skip<TSource>(IEnumerable<TSource>, Int32)	Bypasses a specified number of elements in a sequence and then returns the remaining elements.
SkipLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the elements from source with the last count elements of the source collection omitted.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Take<TSource>(IEnumerable<TSource>, Int32)	Returns a specified number of contiguous elements from the start of a sequence.
Take<TSource>(IEnumerable<TSource>, Range)	Returns a specified range of contiguous elements from a sequence.
TakeLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the last count elements from source.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns elements from a sequence as long as a specified condition is true.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.
ToArray<TSource>(IEnumerable<TSource>)	Creates an array from a IEnumerable<T>.
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	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>)	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>)	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>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.
ToHashSet<TSource>(IEnumerable<TSource>)	Creates a HashSet<T> from an IEnumerable<T>.
ToHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Creates a HashSet<T> from an IEnumerable<T> using the comparer to compare keys.
ToList<TSource>(IEnumerable<TSource>)	Creates a List<T> from an IEnumerable<T>.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.
TryGetNonEnumeratedCount<TSource>(IEnumerable<TSource>, Int32)	Attempts to determine the number of elements in a sequence without forcing an enumeration.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set union of two sequences by using the default equality comparer.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set union of two sequences by using a specified IEqualityComparer<T>.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>)	Produces the set union of two sequences according to a specified key selector function.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set union of two sequences according to a specified key selector function.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Filters a sequence of values based on a predicate.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
Zip<TFirst,TSecond>(IEnumerable<TFirst>, IEnumerable<TSecond>)	Produces a sequence of tuples with elements from the two specified sequences.
Zip<TFirst,TSecond,TThird>(IEnumerable<TFirst>, IEnumerable<TSecond>, IEnumerable<TThird>)	Produces a sequence of tuples with elements from the three specified sequences.
Zip<TFirst,TSecond,TResult>(IEnumerable<TFirst>, IEnumerable<TSecond>, Func<TFirst,TSecond,TResult>)	Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.
AsParallel(IEnumerable)	Enables parallelization of a query.
AsParallel<TSource>(IEnumerable<TSource>)	Enables parallelization of a query.
AsQueryable(IEnumerable)	Converts an IEnumerable to an IQueryable.
AsQueryable<TElement>(IEnumerable<TElement>)	Converts a generic IEnumerable<T> to a generic IQueryable<T>.
Ancestors<T>(IEnumerable<T>)	Returns a collection of elements that contains the ancestors of every node in the source collection.
Ancestors<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.
DescendantNodes<T>(IEnumerable<T>)	Returns a collection of the descendant nodes of every document and element in the source collection.
Descendants<T>(IEnumerable<T>)	Returns a collection of elements that contains the descendant elements of every element and document in the source collection.
Descendants<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
Elements<T>(IEnumerable<T>)	Returns a collection of the child elements of every element and document in the source collection.
Elements<T>(IEnumerable<T>, XName)	Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
InDocumentOrder<T>(IEnumerable<T>)	Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.
Nodes<T>(IEnumerable<T>)	Returns a collection of the child nodes of every document and element in the source collection.
Remove<T>(IEnumerable<T>)	Removes every node in the source collection from its parent node.

Thread Safety

All public and protected members of ConcurrentDictionary<TKey,TValue> are thread-safe and may be used concurrently from multiple threads. However, members accessed through one of the interfaces the ConcurrentDictionary<TKey,TValue> implements, including extension methods, are not guaranteed to be thread safe and may need to be synchronized by the caller.

See also

• Thread-Safe Collections
• How to: Add and Remove Items from a ConcurrentDictionary