Class RowsSourceBase<TDerived, TOutput, TError>

An abstract dataflow worker which repeatedly executes the OnOutputRowsDemandAsync() method when there is RowsPerBuffer demand on the Output port. It also has an ErrorOutput port. The library user must inherit this class and override OnOutputRowsDemandAsync to provide custom functionality.

This class allows the developer to write synchronous or asynchronous code as needed, without having to check for output demand (which simplifies the implementation, as long as no more than RowsPerBuffer rows are sent on each invocation (or demand is checked for explicitly).

The derived class can additionally override RunAsync() to add logic that runs before and after all processing of rows, in which case the base class base.RunAsync() must be called. The derived class (or its user) can also use worker callbacks to add logic.

Use RowsSourceBase<TDerived, TOutput> instead if an ErrorOutput port is not needed. Also see the RowsSourceBase example.

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

The type of the derived worker. Class definition example:

public class MySource<TOutput,TError>
    : RowsSourceBase<MySource<TOutput,TError>,TOutput,TError>
    where TOutput : class, new()
    where TError : class
{ 
    // ...
}
TOutput

The type of each Output row.
TError

The type of each ErrorOutput row.

Constructors

RowsSourceBase(WorkerParent, String, Func<Boolean>)

Initializes a new instance of the RowsSourceBase<TDerived, TOutput, TError> abstract dataflow worker, which repeatedly executes the OnOutputRowsDemandAsync method when there is RowsPerBuffer demand on the Output port.

Declaration
protected RowsSourceBase(WorkerParent workerParent, string workerName, Func<bool> isStartableFunc)
Parameters
Type Name Description
WorkerParent workerParent

The parent worker or worker system that the new child worker will be added to. Cannot be null.
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 "__".

Func<Boolean> isStartableFunc

Function to calculate the worker start constraint; it should return true for startable and false for not startable. Defaults to startable if null.
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

ErrorOutput

Gets the error output port for sending error rows to logging and an optional downstream worker.

Declaration
public ErrorOutputPort<TError> ErrorOutput { get; }
Property Value
Type Description
ErrorOutputPort<TError>

Implements