Class FromTypeColumnMapper<TFrom>

Defines mappings from the (potentially hierarchical) fields, properties, table columns etc. of a source 'from' .NET CLR type (described by FromRowSchema), to a flat list of user supplied or automatically generated target 'to' columns (described by ToRowSchema).

This facility is commonly used by dataflow workers for copying and renaming column data between input fields and properties on the one hand, and external data sources on the other hand.

Members to be mapped can be specified explicitly via name or index (e.g. copy from input column "A" to the fourth output column), as well as implicitly based on name (i.e. AutoName()). A specified field or property on the 'from' side can reside inside a column schema, i.e. a struct that groups multiple fields and properties.

This class does not include the Row() method, and should be used when the Row() method is not supported by the worker in question. Also see IRowMapperCommand which does include that method.

Mappings can be specified with the columnMapperCommandAction parameter, or added by calling the mapping methods Name(String) etc. The mapping result is available in Mappings, which the caller can use to manually perform any tasks, such as copy columns.

Also see the Dataflow Column Mapping and Mapping and Copying examples, as well as IRowMapperCommand and IColumnMapperCommand.

Note: If the mapping commands result in duplicate mappings, an exception will be thrown. Resolve this by either of:

• Specify additional or all name parts in explicit mapping
• Change the column (or schema) names in the from and/or to rows to avoid name clashes
• Restrict auto-mapping to specific column schemas
• Map offending columns explicitly by name (which will exclude them from later auto-mappings)

Inheritance

Object

FromTypeColumnMapper<TFrom>

Implements

IColumnMapperCommand

IFluentInterface

Namespace: actionETL

Assembly: actionETL.dll

Syntax

public class FromTypeColumnMapper<TFrom> : IColumnMapperCommand, IFluentInterface

Type Parameters

Name	Description
TFrom	The source 'from' type.

Constructors

FromTypeColumnMapper(Action<IColumnMapperCommand>)

Initializes a new instance of the FromTypeColumnMapper<TFrom> class, which defines mappings between the fields, properties, table columns etc. of a source 'from' .NET CLR type, to a set of target 'to' column names, automatically created from all source 'from' column names.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

Also see the Dataflow Column Mapping and Mapping and Copying examples, as well as IRowMapperCommand and IColumnMapperCommand.

Declaration

public FromTypeColumnMapper(Action<IColumnMapperCommand> columnMapperCommandAction)

Parameters

Type	Name	Description
Action<IColumnMapperCommand>	columnMapperCommandAction	An action that executes commands that define the column mappings, e.g. mapping two columns using from-name and to-index: cbc => cbc.Name("ColumnA", "0").Name("ColumnB", "1") Set to null to not add any initial mappings.

FromTypeColumnMapper(IEnumerable<String>, Action<IColumnMapperCommand>)

Initializes a new instance of the FromTypeColumnMapper<TFrom> class, which defines mappings between the fields, properties, table columns etc. of a source 'from' .NET CLR type, to a set of user supplied target 'to' columns.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

Also see the Dataflow Column Mapping and Mapping and Copying examples, as well as IRowMapperCommand and IColumnMapperCommand.

Declaration

public FromTypeColumnMapper(IEnumerable<string> toColumnNames, Action<IColumnMapperCommand> columnMapperCommandAction)

Parameters

Type	Name	Description
IEnumerable<String>	toColumnNames	Target 'to' column names.
Action<IColumnMapperCommand>	columnMapperCommandAction	An action that executes commands that define the column mappings, e.g. mapping two columns by name: cbc => cbc.Name("ColumnWithSameName").Name("FromColumn", "ToColumn") Set to null to not add any initial mappings.

Properties

Mappings

Gets the mapper result. It provides the mappings as well as type and other information about the 'from' and 'to' sides.

Declaration

public FromTypeColumnMappings Mappings { get; }

Property Value

Type	Description
FromTypeColumnMappings

Methods

AutoName()

Map automatically by name. Identical names will match, as will partial names where one or more of the left-most parts of the name have been left out. E.g., "Person.Name.FirstName" would automatically map to either of "FirstName" and "Name.FirstName". More matching parts take precedence over fewer matching parts.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

The mapping only considers readable (see CanRead) 'from' columns.

Note: If there are still more than one possible mapping, an exception will be thrown. Resolve this by either of:

• Change the column names in the row(s) to avoid name clashes
• Use one of the overloads that allows restricting the auto-mapping to specific hierarchy names
• Map offending columns individually by name (which will exclude them from later mappings), before calling this auto-mapping method

Declaration

public IColumnMapperCommand AutoName()

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Duplicate matches.

AutoName(Int32)

Map automatically by name. Identical names will match, as will partial names where one or more of the left-most parts of the name have been left out. E.g., "Person.Name.FirstName" would automatically map to either of "FirstName" and "Name.FirstName". More matching parts take precedence over fewer matching parts.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

The mapping only considers readable (see CanRead) 'from' columns.

Note: If there are still more than one possible mapping, an exception will be thrown. Resolve this by either of:

• Change the column names in the row(s) to avoid name clashes
• Use one of the overloads that allows restricting the auto-mapping to specific hierarchy names
• Map offending columns individually by name (which will exclude them from later mappings), before calling this auto-mapping method

Declaration

public IColumnMapperCommand AutoName(int assertNumberOfMatches)

Parameters

Type	Name	Description
Int32	assertNumberOfMatches	Assert number of matches.

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Duplicate matches.

AutoName(Int32, String, String)

Map automatically by name. Identical names will match, as will partial names where one or more of the left-most parts of the name have been left out. E.g., "Person.Name.FirstName" would automatically map to either of "FirstName" and "Name.FirstName". More matching parts take precedence over fewer matching parts.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

The mapping only considers readable (see CanRead) 'from' columns.

Note: If there are still more than one possible mapping, an exception will be thrown. Resolve this by either of:

• Change the column names in the row(s) to avoid name clashes
• Restrict the auto-mapping to specific hierarchy names
• Map offending columns individually by name (which will exclude them from later mappings), before calling this auto-mapping method

Declaration

public IColumnMapperCommand AutoName(int assertNumberOfMatches, string fromHierarchyName, string toHierarchyName)

Parameters

Type	Name	Description
Int32	assertNumberOfMatches	Assert number of matches.
String	fromHierarchyName	Hierarchy from name to include, or null to include all members. Name parts can be omitted from the right, e.g. specifying "Person" will only auto-map from the "Person" member residing directly in the root of the row class, and any descendants of "Person".
String	toHierarchyName	Hierarchy to name to include, or null to include all members. Name parts can be omitted from the right, e.g. specifying "Person" will only auto-map to the "Person" member residing directly in the root of the row class, and any descendants of "Person".

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Duplicate matches.

AutoName(String, String)

Map automatically by name. Identical names will match, as will partial names where one or more of the left-most parts of the name have been left out. E.g., "Person.Name.FirstName" would automatically map to either of "FirstName" and "Name.FirstName". More matching parts take precedence over fewer matching parts.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

The mapping only considers readable (see CanRead) 'from' columns.

Note: If there are still more than one possible mapping, an exception will be thrown. Resolve this by either of:

• Change the column names in the row(s) to avoid name clashes
• Restrict the auto-mapping to specific hierarchy names
• Map offending columns individually by name (which will exclude them from later mappings), before calling this auto-mapping method

Declaration

public IColumnMapperCommand AutoName(string fromHierarchyName, string toHierarchyName)

Parameters

Type	Name	Description
String	fromHierarchyName	Hierarchy from name to include, or null to include all members. Name parts can be omitted from the right, e.g. specifying "Person" will only auto-map from the "Person" member residing directly in the root of the row class, and any descendants of "Person".
String	toHierarchyName	Hierarchy to name to include, or null to include all members. Name parts can be omitted from the right, e.g. specifying "Person" will only auto-map to the "Person" member residing directly in the root of the row class, and any descendants of "Person".

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Duplicate matches.

Index(Int32, Int32)

Map a 'from' column to a 'to' column based on their index in SchemaNodeList.

Declaration

public IColumnMapperCommand Index(int fromSchemaNodeListIndex, int toSchemaNodeListIndex)

Parameters

Type	Name	Description
Int32	fromSchemaNodeListIndex	From index.
Int32	toSchemaNodeListIndex	To index.

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
ArgumentOutOfRangeException	schemaNodeListIndex was outside [0, number of items).
InvalidOperationException	Column already mapped Duplicate column mappings

Name(String)

Map a 'from' column to a 'to' column based on their names.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

Declaration

public IColumnMapperCommand Name(string schemaNodeName)

Parameters

Type	Name	Description
String	schemaNodeName	Name of both the 'from' and 'to' columns. Column schema names can optionally be omitted from the left, as long as the specified name is unique among all columns in the row. E.g., assuming "FirstName" is unique, the following can all identify the same column: "Person.Name.FirstName" "Name.FirstName" "FirstName"

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Member not found Found more than one member match in type Name already mapped
ArgumentNullException	schemaNodeName

Name(String, String)

Map a 'from' column to a 'to' column based on their names.

Column name matching is ordinal case insensitive, but a case sensitive match takes precedence over a case insensitive match.

Declaration

public IColumnMapperCommand Name(string fromSchemaNodeName, string toSchemaNodeName)

Parameters

Type	Name	Description
String	fromSchemaNodeName	Name of the 'from' column. Column schema names can optionally be omitted from the left, as long as the specified name is unique among all columns in the row. E.g., assuming "FirstName" is unique, the following can all identify the same column: "Person.Name.FirstName" "Name.FirstName" "FirstName"
String	toSchemaNodeName	Name of the 'to' column. Column schema names can optionally be omitted from the left, as long as the specified name is unique among all columns in the row. E.g., assuming "FirstName" is unique, the following can all identify the same column: "Person.Name.FirstName" "Name.FirstName" "FirstName"

Returns

Type	Description
IColumnMapperCommand	The IColumnMapperCommand instance itself, which allows chaining commands.

Exceptions

Type	Condition
InvalidOperationException	Member not found Found more than one member match in type Name already mapped
ArgumentNullException	fromSchemaNodeName toSchemaNodeName

Implements

IColumnMapperCommand

IFluentInterface

See Also

IColumnMapperCommand

FromTypeRowMapper<TFrom>

TypeRowMapper<TFrom, TTo>

ToTypeRowMapper<TTo>

TypeColumnCopier<TFrom, TTo>