ConcurrentBag Class

Definition

Represents a thread-safe, unordered collection of objects.

[System.Runtime.InteropServices.ComVisible(false)]
public class ConcurrentBag<T> : System.Collections.Concurrent.IProducerConsumerCollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IReadOnlyCollection<T>
Type Parameters
T

The type of the elements to be stored in the collection.

Inheritance
ConcurrentBag<T>
Attributes
Implements

Inherited Members

System.Object

Examples

The following example shows how to add and remove items from a ConcurrentBag<T>:

using System;
using System.Collections.Concurrent;

class ConcurrentBagDemo
{
    // Demonstrates:
    //      ConcurrentBag<T>.Add()
    //      ConcurrentBag<T>.IsEmpty
    //      ConcurrentBag<T>.TryTake()
    //      ConcurrentBag<T>.TryPeek()
    static void Main()
    {
        // Construct and populate the ConcurrentBag
        ConcurrentBag<int> cb = new ConcurrentBag<int>();
        cb.Add(1);
        cb.Add(2);
        cb.Add(3);

        // Consume the items in the bag
        int item;
        while (!cb.IsEmpty)
        {
            if (cb.TryTake(out item))
                Console.WriteLine(item);
            else
                Console.WriteLine("TryTake failed for non-empty bag");
        }

        // Bag should be empty at this point
        if (cb.TryPeek(out item))
            Console.WriteLine("TryPeek succeeded for empty bag!");
    }

}
Imports System.Collections.Concurrent

Module ConcurrentBagDemo
    ' Demonstrates:
    ' ConcurrentBag<T>.Add()
    ' ConcurrentBag<T>.IsEmpty
    ' ConcurrentBag<T>.TryTake()
    ' ConcurrentBag<T>.TryPeek()
    Sub Main()
        ' Construct and populate the ConcurrentBag
        Dim cb As New ConcurrentBag(Of Integer)()
        cb.Add(1)
        cb.Add(2)
        cb.Add(3)

        ' Consume the items in the bag
        Dim item As Integer
        While Not cb.IsEmpty
            If cb.TryTake(item) Then
                Console.WriteLine(item)
            Else
                Console.WriteLine("TryTake failed for non-empty bag")
            End If
        End While

        ' Bag should be empty at this point
        If cb.TryPeek(item) Then
            Console.WriteLine("TryPeek succeeded for empty bag!")
        End If
    End Sub
End Module

Remarks

Bags are useful for storing objects when ordering doesn't matter, and unlike sets, bags support duplicates. ConcurrentBag<T> is a thread-safe bag implementation, optimized for scenarios where the same thread will be both producing and consuming data stored in the bag.

ConcurrentBag<T> accepts null as a valid value for reference types.

For more information, see the entry FAQ: Are all of the new concurrent collections lock-free? in the Parallel Programming with .NET blog.

Constructors

ConcurrentBag<T>()

Initializes a new instance of the ConcurrentBag<T> class.

ConcurrentBag<T>(IEnumerable<T>)

Initializes a new instance of the ConcurrentBag<T> class that contains elements copied from the specified collection.

Properties

Count

Gets the number of elements contained in the ConcurrentBag<T>.

IsEmpty

Gets a value that indicates whether the ConcurrentBag<T> is empty.

Methods

Add(T)

Adds an object to the ConcurrentBag<T>.

Clear()
CopyTo(T[], Int32)

Copies the ConcurrentBag<T> elements to an existing one-dimensional Array, starting at the specified array index.

GetEnumerator()

Returns an enumerator that iterates through the ConcurrentBag<T>.

ToArray()

Copies the ConcurrentBag<T> elements to a new array.

TryPeek(T)

Attempts to return an object from the ConcurrentBag<T> without removing it.

TryTake(T)

Attempts to remove and return an object from the ConcurrentBag<T>.

Explicit Interface Implementations

IProducerConsumerCollection<T>.TryAdd(T)

Attempts to add an object to the ConcurrentBag<T>.

ICollection.CopyTo(Array, Int32)

Copies the elements of the ICollection to an Array, starting at a particular Array index.

ICollection.IsSynchronized

Gets a value indicating 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.

IEnumerable.GetEnumerator()

Returns an enumerator that iterates through the ConcurrentBag<T>.

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