线程安全的补充

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本篇文章主要介绍了"线程安全的补充 ",主要涉及到线程安全的补充 方面的内容,对于线程安全的补充 感兴趣的同学可以参考一下。

线程安全的补充

发生了 System.ArgumentException
HResult=0x80070057
Message=Source array was not long enough. Check the source index, length, and the array's lower bounds.
Source=<无法计算异常源>
StackTrace:
at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable)
at System.Collections.Generic.List`1.set_Capacity(Int32 value)
at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
at ShoppingPeeker.Web.Framework.PlatformFecture.AutoMappingWord.AutoMappingService.<>c__DisplayClass0_0.<QueryThisKeywordMappings>b__2() in D:\dev\dotnetcore\projects\乐乐乐乐\ShoppingPeeker4.0-2017-062\ShoppingPeeker.Web\Framework\PlatformFecture\AutoMappingWord\AutoMappingService.cs:line 77

https://docs.microsoft.com/en-us/dotnet/api/system.collections.concurrent?view=netframework-4.7
http://www.cnblogs.com/chengxiaohui/articles/5672768.html
http://www.cnblogs.com/Clingingboy/archive/2010/12/06/1897534.html
http://blog.csdn.net/wlanye/article/details/8668089
http://blog.csdn.net/yl2isoft/article/details/12232935
http://blog.csdn.net/zztfj/article/details/5640889

List<T> 线程安全
公共静态 (Shared 在 Visual Basic 中) 这种类型的成员是线程安全。 但不保证所有实例成员都是线程安全的。
则可以安全地执行多个读取的操作 List<T>, ,但如果在读取时修改该集合,可能会出现问题。 若要确保线程安全,读取过程中锁定集合,
或写入操作。 若要启用访问集合以进行读取和写入的多个线程,则必须实现自己的同步。 具有内置同步的集合,
请参阅中的类 System.Collections.Concurrent 命名空间。 本质上是线程 – 安全替代方法,请参阅 ImmutableList<T> 类。


Thread-Safe Collections
2017-3-30 3 min to read Contributors Maira Wenzel Bill Wagner
The .NET Framework 4 introduces the System.Collections.Concurrent namespace, which includes several collection classes that are both thread-safe and scalable. Multiple threads can safely and efficiently add or remove items from these collections, without requiring additional synchronization in user code. When you write new code, use the concurrent collection classes whenever the collection will be writing to multiple threads concurrently. If you are only reading from a shared collection, then you can use the classes in the System.Collections.Generic namespace. We recommend that you do not use 1.0 collection classes unless you are required to target the .NET Framework 1.1 or earlier runtime.
Thread Synchronization in the .NET Framework 1.0 and 2.0 Collections
The collections introduced in the .NET Framework 1.0 are found in the System.Collections namespace. These collections, which include the commonly used ArrayList and Hashtable, provide some thread-safety through the Synchronized property, which returns a thread-safe wrapper around the collection. The wrapper works by locking the entire collection on every add or remove operation. Therefore, each thread that is attempting to access the collection must wait for its turn to take the one lock. This is not scalable and can cause significant performance degradation for large collections. Also, the design is not completely protected from race conditions. For more information, see Synchronization in Generic Collections on the MSDN Web site.
The collection classes introduced in the .NET Framework 2.0 are found in the System.Collections.Generic namespace. These include List<T>, Dictionary<TKey,TValue>, and so on. These classes provide improved type safety and performance compared to the .NET Framework 1.0 classes. However, the .NET Framework 2.0 collection classes do not provide any thread synchronization; user code must provide all synchronization when items are added or removed on multiple threads concurrently.
We recommend the concurrent collections classes in the .NET Framework 4 because they provide not only the type safety of the .NET Framework 2.0 collection classes, but also more efficient and more complete thread safety than the .NET Framework 1.0 collections provide.
Fine-Grained Locking and Lock-Free Mechanisms
Some of the concurrent collection types use lightweight synchronization mechanisms such as SpinLock, SpinWait, SemaphoreSlim, and CountdownEvent, which are new in the .NET Framework 4. These synchronization types typically use busy spinning for brief periods before they put the thread into a true Wait state. When wait times are expected to be very short, spinning is far less computationally expensive than waiting, which involves an expensive kernel transition. For collection classes that use spinning, this efficiency means that multiple threads can add and remove items at a very high rate. For more information about spinning vs. blocking, see SpinLock and SpinWait.
The ConcurrentQueue<T> and ConcurrentStack<T> classes do not use locks at all. Instead, they rely on Interlocked operations to achieve thread-safety.
Note

Because the concurrent collections classes support ICollection, they provide implementations for the IsSynchronized and SyncRoot properties, even though these properties are irrelevant. IsSynchronized always returns false and SyncRoot is always null (Nothing in Visual Basic).
The following table lists the collection types in the System.Collections.Concurrent namespace.
Type Description
BlockingCollection<T> Provides bounding and blocking functionality for any type that implements IProducerConsumerCollection<T>. For more information, see BlockingCollection Overview.
ConcurrentDictionary<TKey,TValue> Thread-safe implementation of a dictionary of key-value pairs.
ConcurrentQueue<T> Thread-safe implementation of a FIFO (first-in, first-out) queue.
ConcurrentStack<T> Thread-safe implementation of a LIFO (last-in, first-out) stack.
ConcurrentBag<T> Thread-safe implementation of an unordered collection of elements.


IProducerConsumerCollection<T> The interface that a type must implement to be used in a BlockingCollection.
Related Topics
Title Description
BlockingCollection Overview Describes the functionality provided by the BlockingCollection<T>type.
How to: Add and Remove Items from a ConcurrentDictionary Describes how to add and remove elements from a ConcurrentDictionary<TKey,TValue>
How to: Add and Take Items Individually from a BlockingCollection Describes how to add and retrieve items from a blocking collection without using the read-only enumerator.
How to: Add Bounding and Blocking Functionality to a Collection Describes how to use any collection class as the underlying storage mechanism for an IProducerConsumerCollection<T> collection.
How to: Use ForEach to Remove Items in a BlockingCollection Describes how to use foreach, (For Each in Visual Basic) to remove all items in a blocking collection.
How to: Use Arrays of Blocking Collections in a Pipeline Describes how to use multiple blocking collections at the same time to implement a pipeline.
How to: Create an Object Pool by Using a ConcurrentBag Shows how to use a concurrent bag to improve performance in scenarios where you can reuse objects instead of continually creating new ones.
Reference


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