The Task Parallel Library (TPL) was introduced in the .NET Framework 4, providing core building blocks and algorithms for parallel computation and asynchrony. This work was centered around the System.Threading.Tasks.Task type, as well as on a few higher-level constructs. These higher-level constructs address a specific subset of common parallel patterns, e.g. Parallel.For/ForEach for delightfully parallel problems expressible as parallelized loops.
While a significant step forward in enabling developers to parallelize their applications, this work did not provide higher-level constructs necessary to tackle all parallel problems or to easily implement all parallel patterns. In particular, it did not focus on problems best expressed with agent-based models or those based on message-passing paradigms. These kinds of problems are quite prevalent in technical computing domains such as finance, biological sciences, oil & gas, and manufacturing.
For TPL Dataflow (TDF), we build upon the foundational layer provided in TPL in .NET 4. TDF is a complementary set of primitives to those primitives delivered in TPL in .NET 4, addressing additional scenarios beyond those directly and easily supported with the original APIs. TPL Dataflow utilizes tasks, concurrent collections, tuples, and other features introduced in .NET 4 to bring support for parallel dataflow-based programming into the .NET Framework. It also directly integrates with new language support for tasks and asynchrony provided by both C# and Visual Basic, and with existing language support in .NET 4 for tasks provided by F#.