Working with Table-Column Data Bands

What is this page about?

This page explains how to work with table-column data bands in templates.

You can build tables growing horizontally rather than vertically by using table-column data bands.

A table-column data band represents a data band, which body occupies a rectangular area of cells of a single document table. The body of such a band starts at the beginning of the top-left cell of a corresponding area and ends at the end of its bottom-right cell. Typically, this area consists of one or several table columns as follows.

...	<<foreach ... -horz>> ...	...	...	...
...	...	...	...	...
...	...	...	... <</foreach>>	...

Note – The horz switch instructs the engine to affect table columns rather than rows.

However, unlike table-row data bands able to capture only whole rows, table-column data bands can occupy columns even partially as shown in the following template snippet.

...	...	...	...	...
...	<<foreach ... -horz>> ...	...	...	...
...	...	...	...	...
...	...	...	... <</foreach>>	...
...	...	...	...	...

Let us consider typical use cases for table-column data bands at first defining ds, a DataSet instance containing DataTable and DataRelation objects according to the following data model.

The most common scenario for a table-column data band is building of a document table that represents a list of items side by side. You can use a template like the following one to achieve this.

Good	<<foreach [s in ds.Sales] -horz>><<[s.Goods.Name]>>	Total:
Pack	<<[s.Packs.Name]>>
Sold Quantity	<<[s.Quantity]>><</foreach>>	<<[ds.Sales.Sum(s => s.Quantity)]>>

In this case, the engine produces a report as follows.

Good	Drinking Water	Drinking Water	Mineral Water	Mineral Water	Total:
Pack	1.5 L	500 ml	1.5 L	500 ml
Sold Quantity	12	27	5	13	57

To grow a document table horizontally by filling it with master‑detail data, you can use nested table‑column data bands like in the following template.

Good/Pack	<<foreach [g in ds.Goods] -horz>><<[g.Name]>>	<<foreach [s in g.Sales] -horz>><<[s.Packs.Name]>>	Total:
Sold Quantity	<<[g.Sales.Sum(s => s.Quantity)]>>	<<[s.Quantity]>><</foreach>><</foreach>>	<<[ds.Sales.Sum(s => s.Quantity)]>>

In this case, the engine produces a report as follows.

Good / Pack	Drinking Water	1.5 L	500 ml	Mineral Water	1.5 L	500 ml	Total:
Sold Quantity	39	12	27	18	5	13	57

You can normally use common data bands nested to table‑column data bands as well like in the following template.

Good	<<foreach [g in ds.Goods] -horz>><<[g.Name]>>
Sold Packs	<<foreach [s in g.Sales]>><<[s.Packs.Name]>> <</foreach>><</foreach>>

In this case, the engine produces a report as follows.

Good	Drinking Water	Mineral Water
Sold Packs	1.5 L 500 ml	1.5 L 500 ml

Note – Table‑column data bands can themselves be nested to table‑row data bands (see “Working with Cross (Pivot) Tables” for details), but not conversely: Nesting of table‑row data bands into table‑column data bands is forbidden.

For more examples of templates for typical scenarios involving table‑column data bands, see “Appendix C. Typical Templates”.

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FAQ

1. Q: How do I declare a table‑column data band in a template?
   A: Use the <<foreach … -horz>> tag inside the cells that belong to the band. The -horz switch tells the engine to repeat the content horizontally across columns. Example: <<foreach [s in ds.Sales] -horz>> <<[s.Goods.Name]>> <<[/foreach]>>.

2. Q: Can I nest table‑column data bands inside each other?
   A: Yes. You can place a <<foreach … -horz>> block inside another <<foreach … -horz>> block to create multi‑level horizontal repetition, such as iterating goods and then packs for each good.

3. Q: Is it possible to nest a table‑row data band inside a table‑column data band?
   A: No. Table‑column data bands may contain other column bands or regular data bands, but a table‑row data band cannot be placed inside a column band. Attempting this will cause the engine to ignore the row band.

4. Q: What does the -horz switch change in the foreach tag?
   A: The -horz switch changes the iteration direction from the default vertical (row‑wise) to horizontal (column‑wise). The engine expands the band across columns, creating a new column for each iteration item.

5. Q: How can I calculate aggregates, like a sum, within a table‑column data band?
   A: Use standard LINQ expressions inside field tags. For example, <<[ds.Sales.Sum(s => s.Quantity)]>> will output the total quantity across all sales rows, even when the band is horizontal. The expression is evaluated in the context of the data set.