/// <summary>
 /// Initializes a new FixedLengthReader with the given schema.
 /// </summary>
 /// <param name="reader">A reader over the fixed-length document.</param>
 /// <param name="schemaSelector">The schema selector configured to determine the schema dynamically.</param>
 /// <param name="options">The options controlling how the fixed-length document is read.</param>
 /// <exception cref="ArgumentNullException">The reader is null.</exception>
 /// <exception cref="ArgumentNullException">The schema selector is null.</exception>
 public FixedLengthReader(TextReader reader, FixedLengthSchemaSelector schemaSelector, FixedLengthOptions options = null)
     : this(reader, null, options, false)
 {
     this.schemaSelector = schemaSelector ?? throw new ArgumentNullException(nameof(schemaSelector));
 }
 public FixedLengthSchemaSelectorWhenBuilder(FixedLengthSchemaSelector selector, Func <string, bool> predicate)
 {
     this.selector  = selector;
     this.predicate = predicate;
 }