Class TransformBase<TDerived, TInput, TOutput>

An abstract dataflow worker with one Input and one Output port, which can be used to create a dataflow transform. The library user must inherit this class and override the RunAsync() method (which will get called once) to add custom functionality. This method should in turn call methods on the Input port to consume rows from the upstream worker, and call methods on the Output port to send rows to the downstream worker.

Note that the input port uses the Default policy. Consider whether this is appropriate, or should be overwritten, see BufferingMode for further details.

Consider using TwoInputTransformBase<TDerived, TLeftInput, TRightInput, TOutput> instead if two input ports are needed. Also see the TransformBase example.

Inheritance
Object
WorkerParent
WorkerBase
WorkerBase<TDerived>
TransformBase<TDerived, TInput, TOutput>
Implements
Inherited Members
Namespace: actionETL
Assembly: actionETL.dll
Syntax
public abstract class TransformBase<TDerived, TInput, TOutput> : WorkerBase<TDerived>, IDisposeOnFinished where TDerived : TransformBase<TDerived, TInput, TOutput> where TInput : class where TOutput : class
Type Parameters
Name Description
TDerived

The type of the derived worker. Class definition example:

public class MyTransform<TInput,TOutput>
    : TransformBase<MyTransform<TInput,TOutput>,TInput,TOutput>
    where TInput : class
    where TOutput : class
{ 
    // ...
}
TInput

The type of each Input row.
TOutput

The type of each Output row.
Remarks

Note: This class only has overloads for asynchronous callbacks, since using synchronous ones would require the callback to block a thread when there is no upstream rows or downstream demand available, which is not appropriate.

Constructors

TransformBase(in DownstreamFactory<TInput>, String)

Initializes a new instance of the TransformBase<TDerived, TInput, TOutput> abstract dataflow worker with one Input and one Output port, which can be used to create a dataflow transform.

Declaration
protected TransformBase(in DownstreamFactory<TInput> downstreamFactory, string workerName)
Parameters
Type Name Description
DownstreamFactory<TInput> downstreamFactory

The downstream factory, which specifies the parent worker and (optionally) the upstream port to link the "first" input port of this dataflow worker to.

Get it from Link when the upstream port is known ahead of time (which is usually the case). Otherwise get it from GetDownstreamFactory<TInput>(), and link the transform or target explicitly using LinkTo(InputPort<TOutput>) or LinkFrom(OutputPortBase<TInput>).

String workerName

Name of the worker.

Set to a prefix plus a trailing "/" (e.g. "MyPrefix-/") to generate a unique name from the prefix plus an increasing number starting at 1.

While less useful, set to null, whitespace or "/" to generate a unique name from the worker type plus an increasing number starting at 1.

The name cannot otherwise contain "/", and cannot start with double underscore "__".

Exceptions
Type Condition
ArgumentException

workerName:

  • Workers with the same parent must have unique names.
  • Worker and worker system names cannot contain '/' or start with double underscore '__'.
ArgumentNullException

workerParent - All workers must have a parent. The top level workers have the worker system as parent.
InvalidOperationException
  • Cannot add child worker to parent which has completed. Are you adding it to the correct parent?
  • Cannot add worker to parent, since its children have been started. Are you adding it to the correct parent?

Properties

Input

Gets the input port for receiving rows from an upstream worker.

Declaration
public InputPort<TInput> Input { get; }
Property Value
Type Description
InputPort<TInput>

Output

Gets the output port for sending rows to the downstream worker.

Declaration
public OutputPort<TOutput> Output { get; }
Property Value
Type Description
OutputPort<TOutput>

Implements