Dynamic report construction

This example demonstrates how to construct a complete report layout—including page setup, static text objects, a report container with a data-bound table—entirely through the DOM API. No pre-designed .lst or .json project file is required.

Overview

The workflow consists of two phases:

Build – Create a project in memory using the DOM, define objects and data bindings, then save.
Export – Load the in-memory project together with a data source and export to the desired format.

Both phases can run without file system access, making this approach suitable for serverless, containerized, or browser-based (WASM) deployments.

Full example

The following service class builds a customer list report and exports it to PDF. All operations happen in-memory.

using combit.Reporting;
using combit.Reporting.DataProviders;
using combit.Reporting.Dom;

public class DynamicReportService
{
    // A4 dimensions in SCM (1/1000 mm).
    private const int PageWidth = 210_000;
    private const int PageHeight = 297_000;

    // Page margins.
    private const int MarginLeft = 20_000;
    private const int MarginTop = 15_000;
    private const int MarginRight = 20_000;
    private const int MarginBottom = 15_000;

    private const int ContentWidth = PageWidth - MarginLeft - MarginRight;
    private const int ContentHeight = PageHeight - MarginTop - MarginBottom;

    // Column widths (must sum to ContentWidth).
    private const int ColId = 15_000;
    private const int ColName = 60_000;
    private const int ColCity = 55_000;
    private const int ColRevenue = 40_000;

    // Title layout.
    private const int TitleHeight = 12_000;
    private const int TitleGap = 2_000;

    /// <summary>
    /// Builds a report layout via the DOM and exports it to PDF.
    /// </summary>
    public byte[] GenerateCustomerReport(IReadOnlyList<Customer> customers)
    {
        ArgumentNullException.ThrowIfNull(customers);

        using MemoryStream projectStream = BuildProject();
        using MemoryStream pdfStream = ExportToPdf(customers, projectStream);

        return pdfStream.ToArray();
    }

    // ──────────────────────────────────────────────────────────────────────
    // Phase 1: Build the project via the DOM
    // ──────────────────────────────────────────────────────────────────────

    private MemoryStream BuildProject()
    {
        using var ll = new ListLabel();
        var projectStream = new MemoryStream();

        using ProjectList project = ll.OpenProject(projectStream, LlProject.List)
            ?? throw new InvalidOperationException("Failed to create project.");

        AddTitle(project);
        AddReportContainer(project);

        project.Save();

        // Return an independent copy so the caller owns the stream lifetime.
        return new MemoryStream(projectStream.ToArray());
    }

    private void AddTitle(ProjectBase project)
    {
        ObjectText title = project.Objects.AddNewText();
        title.Position.Set(MarginLeft, MarginTop, ContentWidth, TitleHeight);

        Paragraph paragraph = title.Paragraphs.AddNew();
        // String literals in LLCP formulas are enclosed in double quotes.
        paragraph.Contents = "\"Customer Revenue Report\"";
    }

    private void AddReportContainer(ProjectBase project)
    {
        ObjectReportContainer container = project.Objects.AddNewReportContainer();

        int containerTop = MarginTop + TitleHeight + TitleGap;
        int containerHeight = ContentHeight - TitleHeight - TitleGap;
        container.Position.Set(MarginLeft, containerTop, ContentWidth, containerHeight);

        SubItemTable table = container.SubItems.AddNewTable();
        // TableId must match the name exposed by the data provider.
        table.TableId = nameof(Customer);

        AddHeaderLine(table);
        AddDataLine(table);
    }

    private void AddHeaderLine(SubItemTable table)
    {
        var headerLine = new TableLineHeader(table.Lines.Header);

        AddTextField(headerLine.Fields, ColId, "\"#\"");
        AddTextField(headerLine.Fields, ColName, "\"Name\"");
        AddTextField(headerLine.Fields, ColCity, "\"City\"");
        AddTextField(headerLine.Fields, ColRevenue, "\"Revenue\"");
    }

    private void AddDataLine(SubItemTable table)
    {
        var dataLine = new TableLineData(table.Lines.Data);

        // Field references follow the pattern "TableName.PropertyName".
        AddTextField(dataLine.Fields, ColId, "Customer.Id");
        AddTextField(dataLine.Fields, ColName, "Customer.Name");
        AddTextField(dataLine.Fields, ColCity, "Customer.City");
        AddTextField(dataLine.Fields, ColRevenue, "Customer.Revenue");
    }

    private static void AddTextField(
        CollectionTableFieldBases fields, int width, string contentsFormula)
    {
        var field = new TableFieldText(fields);
        field.Width = width.ToString();
        field.Contents = contentsFormula;
        field.Wrapping.Line = "1";
        field.Wrapping.Force = "True";
    }

    // ──────────────────────────────────────────────────────────────────────
    // Phase 2: Export the project
    // ──────────────────────────────────────────────────────────────────────

    private static MemoryStream ExportToPdf(
        IReadOnlyList<Customer> customers, MemoryStream projectStream)
    {
        var dataProvider = new ObjectDataProvider(customers);

        using var ll = new ListLabel
        {
            DataSource = dataProvider,
            LicensingInfo = string.Empty
        };

        var pdfStream = new MemoryStream();
        var exportConfig = new ExportConfiguration(
            LlExportTarget.Pdf, pdfStream, projectStream);
        exportConfig.ShowResult = false;

        ll.Export(exportConfig);

        pdfStream.Seek(0, SeekOrigin.Begin);
        return pdfStream;
    }
}

Key concepts

Coordinate system

All positions and sizes use SCM (1/1000 mm) units. A 2 cm margin equals 20,000 SCM.

Formula syntax

DOM property values that represent formulas follow LLCP formula rules:

String literals are enclosed in double quotes: "\"Hello\"".
Data field references use the pattern TableName.FieldName without quotes.

TableId and data binding

The SubItemTable.TableId must match the table name exposed by the data provider. When using ObjectDataProvider with a collection of Customer objects, the table name is the class name ("Customer").

Stream-based workflow

Both OpenProject and ExportConfiguration accept Stream instances. This enables fully in-memory operation without file system dependencies—ideal for Docker, serverless functions, or WebAssembly.

Variations

var footerLine = new TableLineFooter(table.Lines.Footer);
AddTextField(footerLine.Fields, ColId + ColName + ColCity, "\"Total\"");

var totalField = new TableFieldText(footerLine.Fields);
totalField.Width = ColRevenue.ToString();
totalField.Contents = "Sum(Customer.Revenue)";

Using a file path instead of a stream

When file system access is available, you can pass a file path to OpenProject:

using ProjectList project = ll.OpenProject(
    "report.json", LlDomFileMode.Create, LlDomAccessMode.ReadWrite, LlProject.List);

Changing the paper format

To use a different paper format, set the size of the region to the required dimensions:

// First region of the project
var region = project.Regions[0];

// US Letter: 8.5 x 11 inch = 215.9 x 279.4 mm
region.Paper.Extent.Set(new Size(215900, 279400));

Constraints and considerations

DOM manipulation requires understanding of report structure and SCM units. Start with small experiments.
Many DOM properties are typed as string because they may contain dynamic expressions. Pass "True" / "False" for booleans and numeric strings for dimensions.
Always call project.Save() before passing the stream to export.
For WASM deployments, all operations must be synchronous and stream-based because the browser sandbox has no file system access.

Tip

To inspect the generated project structure, save to a file and open it in a text editor—the format is human-readable JSON.

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