task-parallel-library - TPL 默认构造函数 BufferBlock : Value of DataFlowBlockOptions

Question

如果使用默认构造函数构造 TPL BufferBlock，DataFlowBlockOptions 是否无界？换句话说，BufferBlock 的BoundedCapacity 是多少？

As stated in this SO answer , 构造后无法查询或更改 BufferBlock 的值。

Answer 1

您有两种选择可以找出答案:阅读 docs或者自己创建BufferBlock。

来自 TPL 数据流简介:

The majority of the dataflow blocks included in System.Threading.Tasks.Dataflow.dll support the specification of a bounded capacity.

This is the limit on the number of items the block may be storing and have in flight at any one time. By default, this value is initialized to DataflowBlockOptions.Unbounded (-1), meaning that there is no limit.

However, a developer may explicitly specify an upper bound. If a block is already at its capacity when an additional message is offered to it, that message will be postponed.

此外，来自 MSDN :

DataflowBlockOptions is mutable and can be configured through its properties.
When specific configuration options are not set, the following defaults are used:

• TaskScheduler: TaskScheduler.Default
• MaxMessagesPerTask: DataflowBlockOptions.Unbounded (-1)
• CancellationToken: CancellationToken.None
• BoundedCapacity: DataflowBlockOptions.Unbounded (-1)

Dataflow blocks capture the state of the options at their construction.
Subsequent changes to the provided DataflowBlockOptions instance should not affect the behavior of a dataflow block.

您始终可以从调试器查看私有(private)成员:

您也可以尝试通过反射来获取/设置它们，但确实不推荐这样做。