ConcurrentQueue<T>
Class
Definition
Represents a thread-safe first in-first out (FIFO) collection.
In This Article
[System.Runtime.InteropServices.ComVisible(false)]
public class ConcurrentQueue<T> : System.Collections.Concurrent.IProducerConsumerCollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IReadOnlyCollection<T>
Type Parameters
T
The type of the elements contained in the queue.
Inheritance
Attributes
Implements
Inherited Members
System.Object
Examples
The following example shows how to use a ConcurrentQueue<T> to enqueue and dequeue items:
using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;
class CQ_EnqueueDequeuePeek
{
// Demonstrates:
// ConcurrentQueue<T>.Enqueue()
// ConcurrentQueue<T>.TryPeek()
// ConcurrentQueue<T>.TryDequeue()
static void Main ()
{
// Construct a ConcurrentQueue.
ConcurrentQueue<int> cq = new ConcurrentQueue<int>();
// Populate the queue.
for (int i = 0; i < 10000; i++) cq.Enqueue(i);
// Peek at the first element.
int result;
if (!cq.TryPeek(out result))
{
Console.WriteLine("CQ: TryPeek failed when it should have succeeded");
}
else if (result != 0)
{
Console.WriteLine("CQ: Expected TryPeek result of 0, got {0}", result);
}
int outerSum = 0;
// An action to consume the ConcurrentQueue.
Action action = () =>
{
int localSum = 0;
int localValue;
while (cq.TryDequeue(out localValue)) localSum += localValue;
Interlocked.Add(ref outerSum, localSum);
};
// Start 4 concurrent consuming actions.
Parallel.Invoke(action, action, action, action);
Console.WriteLine("outerSum = {0}, should be 49995000", outerSum);
}
}
Imports System.Collections.Concurrent
Imports System.Threading
Imports System.Threading.Tasks
Class TestQueue
' Demonstrates:
' ConcurrentQueue<T>.Enqueue()
' ConcurrentQueue<T>.TryPeek()
' ConcurrentQueue<T>.TryDequeue()
Shared Sub Main()
' Construct a ConcurrentQueue
Dim cq As New ConcurrentQueue(Of Integer)()
' Populate the queue
For i As Integer = 0 To 9999
cq.Enqueue(i)
Next
' Peek at the first element
Dim result As Integer
If Not cq.TryPeek(result) Then
Console.WriteLine("CQ: TryPeek failed when it should have succeeded")
ElseIf result <> 0 Then
Console.WriteLine("CQ: Expected TryPeek result of 0, got {0}", result)
End If
Dim outerSum As Integer = 0
' An action to consume the ConcurrentQueue
Dim action As Action =
Sub()
Dim localSum As Integer = 0
Dim localValue As Integer
While cq.TryDequeue(localValue)
localSum += localValue
End While
Interlocked.Add(outerSum, localSum)
End Sub
' Start 4 concurrent consuming actions
Parallel.Invoke(action, action, action, action)
Console.WriteLine("outerSum = {0}, should be 49995000", outerSum)
End Sub
End Class
Remarks
Constructors
Properties
Methods
Explicit Interface Implementations
Extension Methods
ToImmutableArray<TSource>(IEnumerable<TSource>)
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)
ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>)
ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>)
ToImmutableDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>)
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)
ToImmutableHashSet<TSource>(IEnumerable<TSource>)
ToImmutableHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)
ToImmutableList<TSource>(IEnumerable<TSource>)
ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>)
ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IComparer<TKey>)
ToImmutableSortedDictionary<TKey,TValue>(IEnumerable<KeyValuePair<TKey,TValue>>, IComparer<TKey>, IEqualityComparer<TValue>)
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>)
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>, IEqualityComparer<TValue>)
ToImmutableSortedSet<TSource>(IEnumerable<TSource>)
ToImmutableSortedSet<TSource>(IEnumerable<TSource>, IComparer<TSource>)
CopyToDataTable<T>(IEnumerable<T>)
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)
Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)
Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)
Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)
All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
Any<TSource>(IEnumerable<TSource>)
Any<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
Append<TSource>(IEnumerable<TSource>, TSource)
AsEnumerable<TSource>(IEnumerable<TSource>)
Average(IEnumerable<Decimal>)
Average(IEnumerable<Double>)
Average(IEnumerable<Int32>)
Average(IEnumerable<Int64>)
Average(IEnumerable<Nullable<Decimal>>)
Average(IEnumerable<Nullable<Double>>)
Average(IEnumerable<Nullable<Int32>>)
Average(IEnumerable<Nullable<Int64>>)
Average(IEnumerable<Nullable<Single>>)
Average(IEnumerable<Single>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Double>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)
Average<TSource>(IEnumerable<TSource>, Func<TSource,Single>)
Cast<TResult>(IEnumerable)
Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
Contains<TSource>(IEnumerable<TSource>, TSource)
Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)
Count<TSource>(IEnumerable<TSource>)
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
DefaultIfEmpty<TSource>(IEnumerable<TSource>)
DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)
Distinct<TSource>(IEnumerable<TSource>)
Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)
ElementAt<TSource>(IEnumerable<TSource>, Int32)
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Int32)
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
First<TSource>(IEnumerable<TSource>)
First<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
FirstOrDefault<TSource>(IEnumerable<TSource>)
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>)
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>, IEqualityComparer<TKey>)
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)
Last<TSource>(IEnumerable<TSource>)
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
LastOrDefault<TSource>(IEnumerable<TSource>)
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
LongCount<TSource>(IEnumerable<TSource>)
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
Max(IEnumerable<Decimal>)
Max(IEnumerable<Double>)
Max(IEnumerable<Int32>)
Max(IEnumerable<Int64>)
Max(IEnumerable<Nullable<Decimal>>)
Max(IEnumerable<Nullable<Double>>)
Max(IEnumerable<Nullable<Int32>>)
Max(IEnumerable<Nullable<Int64>>)
Max(IEnumerable<Nullable<Single>>)
Max(IEnumerable<Single>)
Max<TSource>(IEnumerable<TSource>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Double>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)
Max<TSource>(IEnumerable<TSource>, Func<TSource,Single>)
Max<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)
Min(IEnumerable<Decimal>)
Min(IEnumerable<Double>)
Min(IEnumerable<Int32>)
Min(IEnumerable<Int64>)
Min(IEnumerable<Nullable<Decimal>>)
Min(IEnumerable<Nullable<Double>>)
Min(IEnumerable<Nullable<Int32>>)
Min(IEnumerable<Nullable<Int64>>)
Min(IEnumerable<Nullable<Single>>)
Min(IEnumerable<Single>)
Min<TSource>(IEnumerable<TSource>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Double>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)
Min<TSource>(IEnumerable<TSource>, Func<TSource,Single>)
Min<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)
OfType<TResult>(IEnumerable)
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)
Prepend<TSource>(IEnumerable<TSource>, TSource)
Reverse<TSource>(IEnumerable<TSource>)
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>)
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
Single<TSource>(IEnumerable<TSource>)
Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
SingleOrDefault<TSource>(IEnumerable<TSource>)
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
Skip<TSource>(IEnumerable<TSource>, Int32)
SkipLast<TSource>(IEnumerable<TSource>, Int32)
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)
Sum(IEnumerable<Decimal>)
Sum(IEnumerable<Double>)
Sum(IEnumerable<Int32>)
Sum(IEnumerable<Int64>)
Sum(IEnumerable<Nullable<Decimal>>)
Sum(IEnumerable<Nullable<Double>>)
Sum(IEnumerable<Nullable<Int32>>)
Sum(IEnumerable<Nullable<Int64>>)
Sum(IEnumerable<Nullable<Single>>)
Sum(IEnumerable<Single>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Double>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Single>)
Take<TSource>(IEnumerable<TSource>, Int32)
TakeLast<TSource>(IEnumerable<TSource>, Int32)
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)
ToArray<TSource>(IEnumerable<TSource>)
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)
ToHashSet<TSource>(IEnumerable<TSource>)
ToHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)
ToList<TSource>(IEnumerable<TSource>)
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)
Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)
Zip<TFirst,TSecond,TResult>(IEnumerable<TFirst>, IEnumerable<TSecond>, Func<TFirst,TSecond,TResult>)
AsParallel(IEnumerable)
AsParallel<TSource>(IEnumerable<TSource>)
AsQueryable(IEnumerable)
AsQueryable<TElement>(IEnumerable<TElement>)
Ancestors<T>(IEnumerable<T>)
Ancestors<T>(IEnumerable<T>, XName)
AncestorsAndSelf(IEnumerable<XElement>)
AncestorsAndSelf(IEnumerable<XElement>, XName)
Attributes(IEnumerable<XElement>)
Attributes(IEnumerable<XElement>, XName)
DescendantNodes<T>(IEnumerable<T>)
DescendantNodesAndSelf(IEnumerable<XElement>)
Descendants<T>(IEnumerable<T>)
Descendants<T>(IEnumerable<T>, XName)
DescendantsAndSelf(IEnumerable<XElement>)
DescendantsAndSelf(IEnumerable<XElement>, XName)
Elements<T>(IEnumerable<T>)
Elements<T>(IEnumerable<T>, XName)
InDocumentOrder<T>(IEnumerable<T>)
Nodes<T>(IEnumerable<T>)
Remove(IEnumerable<XAttribute>)
Remove<T>(IEnumerable<T>)
Thread Safety
All public and protected members of ConcurrentQueue<T> are thread-safe and may be used concurrently from multiple threads.