Class SkipTransformer<T>

Namespace

Wolfgang.Etl.Transformers

Assembly

Wolfgang.Etl.Transformers.dll

A transformer that skips a fixed number of items from the start of the input sequence and yields the rest unchanged.

public sealed class SkipTransformer<T> : ITransformAsync<T, T> where T : notnull

Type Parameters

T

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

Inheritance

object

SkipTransformer<T>

Implements

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>)

Examples

// skip the first row (header) before processing the rest
var dataOnly = new SkipTransformer<Row>(count: 1);

Remarks

SkipTransformer<T> is the transformer equivalent of LINQ's Skip<TSource>(IEnumerable<TSource>, int): it discards the first Count items and yields everything after them.

A count of 0 or negative is not an error - the transformer yields the source unchanged (matches the BCL contract for Enumerable.Skip). When count <= 0 the source is returned directly without a wrapping iterator, so this is essentially free.

Useful for skipping headers, hopping past already-processed rows, or as a building block in composed pipelines when the upstream extractor does not expose a row-skip property.

Implements only Wolfgang.Etl.Abstractions.ITransformAsync<TSource, TDestination> - no progress, no cancellation, no Skip/Max - to keep the hot loop minimal.

Constructors

SkipTransformer(int)

Initializes a new instance that skips the first count items.

public SkipTransformer(int count)

Parameters

count int

The number of items to skip from the start of the source. A value of 0 or less yields the source unchanged.

Properties

Count

The number of items this transformer will skip from the start of the source.

public int Count { get; }

Property Value

int

Methods

TransformAsync(IAsyncEnumerable<T>)

Asynchronously yields all items from items after skipping the first Count of them.

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

Parameters

items IAsyncEnumerable<T>

The asynchronous source sequence.

Returns

IAsyncEnumerable<T>

An asynchronous sequence containing the items from items after position Count. Empty if the source has Count or fewer items. The source items directly when Count is 0 or negative.

Exceptions

ArgumentNullException

items is null.