Class PassThroughTransformer<T>

Namespace: Wolfgang.Etl.Transformers

Assembly: Wolfgang.Etl.Transformers.dll

A transformer that yields each item from the input sequence unchanged.

public sealed class PassThroughTransformer<T> : ITransformWithCancellationAsync<T, T>, ITransformAsync<T, T> where T : notnull

Type Parameters

T: The type of items flowing through the transformer. Must be non-null.

Inheritance: object

PassThroughTransformer<T>

Implements: ITransformWithCancellationAsync<T, T>

ITransformAsync<T, T>

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Extension Methods: TransformerExtensions.Then<TSource, TIntermediate, TDestination>(ITransformAsync<TSource, TIntermediate>, ITransformAsync<TIntermediate, TDestination>)

TransformerExtensions.Then<TSource, TIntermediate, TDestination>(ITransformWithCancellationAsync<TSource, TIntermediate>, ITransformWithCancellationAsync<TIntermediate, TDestination>)

Examples

var transformer = new PassThroughTransformer<Customer>();
await foreach (var customer in transformer.TransformAsync(source))
{
    // items are yielded unchanged
}

Remarks

PassThroughTransformer<T> is useful as:

A placeholder in an ETL pipeline when a transformer is required by the pipeline shape but no transformation is needed.
A default implementation in dependency injection, letting consumers swap in a real transformer later without restructuring the pipeline.
A test seam for verifying extractor/loader behaviour without a real transformer in the way.

This class deliberately does not inherit from Wolfgang.Etl.Abstractions.TransformerBase<TSource, TDestination, TProgress>. Because it performs no work, it does not need progress reporting, skip/max item counts, or a reporting timer, and implementing the interface directly keeps the type minimal and allocation-free.

Formerly known internally as NoOpTransformer.

Constructors

PassThroughTransformer()

Initializes a new instance of the PassThroughTransformer<T> class.

public PassThroughTransformer()

Methods

TransformAsync(IAsyncEnumerable<T>)

Asynchronously yields each item from items unchanged.

public IAsyncEnumerable<T> TransformAsync(IAsyncEnumerable<T> items)

Parameters

items IAsyncEnumerable<T>: The asynchronous source sequence.

Returns

IAsyncEnumerable<T>: An asynchronous sequence containing the same items as items, in the same order.

Remarks

Because no transformation is applied, this overload returns the source sequence directly without allocating a wrapping iterator. Any cancellation must be supplied by the caller via .WithCancellation(token) on the returned sequence, or by using the TransformAsync(IAsyncEnumerable<T>, CancellationToken) overload.

Exceptions

ArgumentNullException: items is null.

TransformAsync(IAsyncEnumerable<T>, CancellationToken)

Asynchronously yields each item from items unchanged, observing the supplied token for cancellation.

public IAsyncEnumerable<T> TransformAsync(IAsyncEnumerable<T> items, CancellationToken token)

Parameters

items IAsyncEnumerable<T>: The asynchronous source sequence.
token CancellationToken: A token to observe while enumerating the source sequence.

Returns

IAsyncEnumerable<T>: An asynchronous sequence containing the same items as items, in the same order.

Exceptions

ArgumentNullException: items is null.
OperationCanceledException: token was cancelled before or during enumeration.