Class FixedWidthSchemaBuilder<T>

Namespace: Wolfgang.Etl.FixedWidth

Assembly: Wolfgang.Etl.FixedWidth.dll

Builds a FixedWidthSchema for T from a fluent, type-safe code API instead of [FixedWidthField] / [FixedWidthSkip] attributes (#23). Use it when the record type is not yours to decorate, when you prefer configuration-as-code, or when the layout is built dynamically. The resulting schema is equivalent to one resolved from attributes — assign it to Schema / Schema to use it, or inspect it with Fields / ToDiagram().

public sealed class FixedWidthSchemaBuilder<T> where T : notnull

Type Parameters

T: The record type the schema describes.

Inheritance: object

FixedWidthSchemaBuilder<T>

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Examples

var schema = new FixedWidthSchemaBuilder<CustomerRecord>()
    .Field(r => r.CustomerId, index: 0, length: 8)
    .Field(r => r.Name, index: 1, length: 30)
    .Skip(index: 2, length: 5)
    .Field(r => r.Balance, index: 3, length: 9, alignment: FieldAlignment.Right, format: "0000000.00")
    .Build();

var extractor = new FixedWidthExtractor<CustomerRecord>(reader) { Schema = schema };

Methods

Build()

Validates the accumulated fields and skips and produces the immutable FixedWidthSchema.

public FixedWidthSchema Build()

Returns

FixedWidthSchema: The resolved schema.

Exceptions

InvalidOperationException: No fields were defined, or two columns share the same index.

Field<TProperty>(Expression<Func<T, TProperty>>, int, int, FieldAlignment, char, string?, string?, NumberStyles?, bool)

Adds a mapped field. The index is a zero-based column ordinal (matching [FixedWidthField(index, length)]); start positions are computed by summing the lengths of all lower-indexed columns, so indexes only need to be unique, not contiguous.

public FixedWidthSchemaBuilder<T> Field<TProperty>(Expression<Func<T, TProperty>> selector, int index, int length, FieldAlignment alignment = FieldAlignment.Left, char pad = ' ', string? format = null, string? header = null, NumberStyles? numberStyles = null, bool trimValue = true)

Parameters

selector Expression<Func<T, TProperty>>: A simple property access expression, e.g. r => r.Name.
index int: The zero-based column index. Must be unique across fields and skips.
length int: The field width in characters. Must be greater than zero.
alignment FieldAlignment: Padding alignment for writing. Defaults to Left.
pad char: Pad character for writing. Defaults to ' '.
format string: Optional format string for parsing/formatting the value.
header string: Optional header label; defaults to the property name when writing headers.
numberStyles NumberStyles?: Optional NumberStyles for numeric parsing; defaults to the type's natural style.
trimValue bool: Whether to trim whitespace from the extracted value. Defaults to true.

Returns

FixedWidthSchemaBuilder<T>: The same builder, for chaining.

Type Parameters

TProperty: The property type.

Exceptions

ArgumentNullException: selector is null.
ArgumentException: selector is not a simple property access.
ArgumentOutOfRangeException: index is negative or length is not positive.
InvalidOperationException: The selected property has no public setter.

Skip(int, int, string?)

Adds a skipped column — a range in the file mapped to no property. Its width still contributes to the positions of later fields.

public FixedWidthSchemaBuilder<T> Skip(int index, int length, string? message = null)

Parameters

index int: The zero-based column index. Must be unique across fields and skips.
length int: The skipped width in characters. Must be greater than zero.
message string: Optional note describing the skipped column (surfaced by schema introspection).

Returns

FixedWidthSchemaBuilder<T>: The same builder, for chaining.

Exceptions

ArgumentOutOfRangeException: index is negative or length is not positive.