RDL Editor - Data & Expressions

Binding fields

Every textbox and table cell has a Bind to field / insert snippet dropdown under its Value:

• Pick a dataset field → the value becomes =Fields!X.Value. The list comes straight from the report's <DataSets> — you never type a field name blind.
• Pick a snippet → a ready-made pattern is inserted with this report's dataset/field names already substituted.

Expression inputs (sort, filter, group expressions, Hidden) autocomplete from the same pool: type = and the suggestions appear.

What the autocomplete knows

Prefix	Source
=Fields!X.Value	The report's dataset fields
=Parameters!X.Value	The report's parameters
=ReportItems!X.Value	Every textbox name in this layout — the editor knows them all, so the header/footer helper pattern (below) is two keystrokes instead of memory work
=Globals!…, =User!…	PageNumber, TotalPages, ExecutionTime, ReportName, RenderFormat.Name, Language

The snippet library

Snippet	Pattern
Page N of M	="Page " & Globals!PageNumber & " of " & Globals!TotalPages
Print date/time	=Format(Now(), "yyyy-MM-dd HH:mm")
Document-level value	=First(Fields!X.Value, "DataSet_Result") — for values constant per document shown in a grouped area
Sum	=Sum(Fields!X.Value) — the result depends on where the textbox sits (group footer = group total)
Conditional text / color	=IIF(Fields!X.Value < 0, "Red", "Black")
Hide when blank	=IsNothing(Fields!X.Value) Or Fields!X.Value = "" — for row visibility on optional lines (Address 2 etc.); hiding only the textbox leaves an empty row
Alternating row color	=IIF(RowNumber(Nothing) Mod 2 = 0, "WhiteSmoke", "White") — scope RowNumber("GroupName") to reset per group
Hidden body value	=ReportItems!TextboxName.Value — see below

The page header/footer pattern

Page headers and footers cannot read dataset fields directly. The BC convention:

1. Put the value in a textbox in the body (often inside the line table so it's on every page).
2. Hide it; give it a clear name (HiddenDocumentNo, not Textbox183).
3. In the header/footer textbox: =ReportItems!HiddenDocumentNo.Value.

The editor enforces the rules around this pattern with inline warnings (chapter 7): Fields! in a page band, more than one ReportItems! per header expression, references to textboxes that don't exist, and the Word-export page-number trap (Globals!PageNumber.ToString freezes — use plain Globals!PageNumber).

One more constraint from the renderer: the referenced textbox must actually be on the rendered page — a body textbox that only appears on page 1 makes the header value blank (or #Error) on page 2+. Put the hidden helper in a repeating row when it's needed on every page.

Format strings

The Format field (Font section) sets the .NET format string for numbers and dates:

N2            #,##0.00          #,##0.00;(#,##0.00)
yyyy-MM-dd    dd/MM/yyyy

Format the display, not the data: a value that must sum or sort correctly should stay numeric in the dataset and get its formatting here.

Visibility

Items, cells, table rows/columns, and group members all have a Visibility section: a Hidden value (true, false, or expression) and a Toggle item (the textbox that gets the +/− drilldown control).

The semantics feel backwards at first and the editor labels them accordingly: the expression returns true to HIDE. Statically hidden things render dimmed on the canvas, like Report Builder.

Interactive sort

The Interactive sort (expr) field on a textbox/cell (typically a column header) adds the click-to-sort arrows in interactive preview: set it to the field the column shows, e.g. =Fields!Amount.Value.

Keep business logic in AL

Layout expressions are for presentation: hiding blank rows, coloring negatives, formatting, concatenating display text, page numbers. Tax math, discounts, currency conversion, compliance decisions belong in the AL report — calculated once, delivered as dataset fields. Two technical reasons beyond hygiene: IIF() evaluates both branches (a guarded division can still fail), and layout filters don't reduce the data BC processes.