public static string Serialize(PropertyExtractorCollection extractors)
{
if (extractors == null || !extractors.Any())
{
return(null);
}
using (var stringWriter = new StringWriter())
using (var writer = XmlWriter.Create(stringWriter, new XmlWriterSettings {
OmitXmlDeclaration = true
}))
{
extractors.WriteXml(writer);
writer.Flush();
return(stringWriter.ToString());
}
}
/// <summary>
/// Merges two sets of <see cref="PropertyExtractor"/>-derived extractors by honoring their <see cref="Precedence"/> and assuming that this <see
/// cref="PropertyExtractorCollection"/> instance contains the <see cref="PropertyExtractor"/>s configured by XML schema annotations and that <see
/// cref="PropertyExtractorCollection"/> being merged into contains the <see cref="PropertyExtractor"/>s configured by the pipeline.
/// </summary>
/// <param name="pipelineExtractors">
/// The <see cref="PropertyExtractor"/>s configured by the pipeline.
/// </param>
/// <returns>
/// The result of the merge between two sets of <see cref="PropertyExtractor"/>-derived extractors.
/// </returns>
/// <remarks>
/// <para>
/// The merge algorithm proceeds as follows:
/// <list type="bullet">
/// <item>
/// The <see cref="Precedence"/> of the <see cref="PropertyExtractor"/>s configured by XML schema annotations is irrelevant and discarded, no matter
/// what its value may be. In other words, only the <see cref="Precedence"/> of the <see cref="PropertyExtractor"/>s configured by the pipeline is
/// actually relevant. If unspecified, the <see cref="Precedence"/> of the <see cref="PropertyExtractor"/>s configured by the pipeline will be assumed
/// to be given to the <see cref="ExtractorPrecedence.Schema"/>.
/// </item>
/// <item>
/// If the <see cref="Precedence"/> of the pipeline <see cref="PropertyExtractor"/>s is given to the <see cref="ExtractorPrecedence.Schema"/> then any
/// <see cref="PropertyExtractor"/> <b>redefined</b> by the pipeline will be ignored. In other words, for these particular <see
/// cref="PropertyExtractor"/>s <b>redefined</b> by the pipeline, only their configuration done by the schema annotations will be retained. The <see
/// cref="PropertyExtractor"/>s defined either only by the annotations or only by the pipeline will of course be part of the resulting merge.
/// </item>
/// <item>
/// If the <see cref="Precedence"/> of the pipeline <see cref="PropertyExtractor"/>s is set to <see cref="ExtractorPrecedence.SchemaOnly"/> then any
/// <see cref="PropertyExtractor"/> defined by the pipeline will be ignored provided that there are <see cref="PropertyExtractor"/>s configured by XML
/// schema annotations. In other words, if there are <see cref="PropertyExtractor"/>s configured by annotations then the merge operation will return
/// only these and discard any <see cref="PropertyExtractor"/>s configured by the pipeline. But if there are no <see cref="PropertyExtractor"/>s
/// configured by annotations then the merge operation will return only the <see cref="PropertyExtractor"/>s configured by the the pipeline.
/// </item>
/// <item>
/// If the <see cref="Precedence"/> of the pipeline <see cref="PropertyExtractor"/>s is given to the <see cref="ExtractorPrecedence.Pipeline"/> then
/// any <see cref="PropertyExtractor"/> <b>redefined</b> by the pipeline will have precedence over the one defined by the annotations. In other words,
/// for these particular <see cref="PropertyExtractor"/>s <b>redefined</b> by the pipeline, only their configuration done by the pipeline will be
/// retained. The <see cref="PropertyExtractor"/>s defined either only by the annotations or only by the pipeline will of course be part of the
/// resulting merge.
/// </item>
/// <item>
/// If the <see cref="Precedence"/> of the pipeline <see cref="PropertyExtractor"/>s is set to <see cref="ExtractorPrecedence.PipelineOnly"/> then any
/// <see cref="PropertyExtractor"/> defined by XML schema annotations will be ignored provided that there are <see cref="PropertyExtractor"/>s
/// configured by the pipeline. In other words, if there are <see cref="PropertyExtractor"/>s configured by the pipeline then the merge operation will
/// return only these and discard any <see cref="PropertyExtractor"/>s configured by annotations. But if there are no <see cref="PropertyExtractor"/>s
/// configured by the pipeline then the merge operation will return only the <see cref="PropertyExtractor"/>s configured by annotations.
/// </item>
/// <item>
/// Notice that <see cref="PropertyExtractor"/>s whose <see cref="PropertyExtractor.ExtractionMode"/> is set to <see cref="ExtractionMode.Ignore"/>
/// will be filtered out of the resulting set of <see cref="PropertyExtractor"/>s only after the merge operation have proceeded. This could therefore
/// lead to interesting results if the <see cref="Precedence"/> of the pipeline's <see cref="PropertyExtractor"/>s is either set to <see
/// cref="ExtractorPrecedence.Pipeline"/> or <see cref="ExtractorPrecedence.Schema"/>.
/// </item>
/// </list>
/// </para>
/// </remarks>
public IEnumerable <PropertyExtractor> Union(PropertyExtractorCollection pipelineExtractors)
{
if (pipelineExtractors == null)
{
throw new ArgumentNullException(nameof(pipelineExtractors));
}
// notice that Linq.Union enumerates first and second in that order and yields each element that has not
// already been yielded; see https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.union
var schemaExtractors = Extractors;
var mergedExtractors = pipelineExtractors.Precedence switch {
ExtractorPrecedence.Schema => schemaExtractors.Union(pipelineExtractors, _lambdaComparer),
ExtractorPrecedence.SchemaOnly => schemaExtractors.Any() ? schemaExtractors : pipelineExtractors,
ExtractorPrecedence.Pipeline => pipelineExtractors.Union(schemaExtractors, _lambdaComparer),
ExtractorPrecedence.PipelineOnly => pipelineExtractors.Any() ? pipelineExtractors : schemaExtractors,
_ => throw new InvalidOperationException($"Unknown ExtractorPrecedence value '{pipelineExtractors.Precedence}'.")
};
// filter out extractors to be ignored
return(mergedExtractors.Where(pe => pe.ExtractionMode != ExtractionMode.Ignore).ToArray());
}
