PDFsharp & MigraDoc Forum

using System;
using System.Collections.Generic;
using MigraDoc.DocumentObjectModel;
using MigraDoc.DocumentObjectModel.Tables;
using MigraDoc.Rendering;

namespace YourProjectNamespace;

static class MigraDocHelper {
    /// <summary>
    /// Method for fixing the MergeDown bug.
    /// The method overrides the RowHeightRule of the last row, increasing the row height by the missing height value.
    /// </summary>
    /// <remarks>
    /// This fix internally clones the part of the table that contains the rows affected by the MergeDown.
    /// So, if there is a Cell inside this part of the table that has a MergeDown that continues further than this part of table, then an exception will be thrown.
    /// </remarks>
    /// <param name="pageAndStylesConfig">Configure the document according to how your page is configured and what styles are used in the document.</param>
    /// <param name="cell">Cell that has MergeDown</param>
    public static void MergedCellHeightFix(Action<Document> pageAndStylesConfig, Cell cell)
    {
        if (cell.Table == null || cell.Row == null)
            throw new Exception("Cell must be added to the table.");

        Table table = cell.Table;
        Row row = cell.Row;
        //Most likely bug occurs if MergeDown greater then 1
        if (cell.MergeDown > 1)
        {
            Table partiallyClonedTable = CreatePartiallyСlonedTable(table, row.Index, cell.MergeDown + 1);
            Unit partiallyClonedTableHeight = CalculateTablesHeight(pageAndStylesConfig, [partiallyClonedTable], BordersRenderOption.WithoutTopAndBottom);
            Unit cellHeight = CalculateCellHeight(pageAndStylesConfig, cell);
            if (cellHeight > partiallyClonedTableHeight)
            {
                Unit diffHeight = cellHeight - partiallyClonedTableHeight;

                Row lastRowOfMerge = table.Rows[row.Index + cell.MergeDown];
                Unit finalRowOfMergeHeight = CalculateRowHeight(pageAndStylesConfig, lastRowOfMerge);
                lastRowOfMerge.HeightRule = RowHeightRule.Exactly;
                lastRowOfMerge.Height = Unit.FromPoint(finalRowOfMergeHeight.Point + diffHeight.Point);
            }
        }
    }
    /// <summary>
    /// The method clones elements from Cell.Elements into the renderer to calculate the height.
    /// </summary>
    private static Unit CalculateCellHeight(Action<Document> pageAndStylesConfig, Cell cellFromInputTable)
    {
        Unit occupiedSpaceHeight = Unit.Zero;
        var document = new Document();
        var section = document.AddSection();
        pageAndStylesConfig(document);
        var table = new Table
        {
            Borders =
            {
                Width = 0
            },
        };
        Column? columnFromInputTable = cellFromInputTable.Column;
        if (columnFromInputTable == null) throw new Exception("Cell must be added to the table.");
        Column column = table.AddColumn();
        column.Width = columnFromInputTable.Width;
        column.Format = columnFromInputTable.Format.Clone();
        column.LeftPadding = columnFromInputTable.LeftPadding;
        column.RightPadding = columnFromInputTable.RightPadding;

        Row row = table.AddRow();
        Cell cell = row.Cells[0];
        foreach (var _element in cellFromInputTable.Elements)
        {
            switch (_element)
            {
                case MigraDoc.DocumentObjectModel.Paragraph _paragraph:
                    cell.Add(_paragraph.Clone());
                    break;
                case MigraDoc.DocumentObjectModel.Shapes.Image _image:
                    cell.Add(_image.Clone());
                    break;
                case MigraDoc.DocumentObjectModel.Shapes.Charts.Chart _chart:
                    cell.Add(_chart.Clone());
                    break;
                case MigraDoc.DocumentObjectModel.Shapes.TextFrame _textFrame:
                    cell.Add(_textFrame.Clone());
                    break;
                default:
                    throw new NotImplementedException();
            }
        }
        section.Add(table);

        Unit occupiedHeight = CalculateTablesHeightFromRender(document);
        return occupiedHeight;
    }

    public enum BordersRenderOption
    {
        All,
        WithoutTopAndBottom
    }
    private static Unit CalculateRowHeight(Action<Document> pageAndStylesConfig, Row row)
    {
        if (row.Table == null)
            throw new Exception("Row must be added to the table.");

        Table table = row.Table;
        Table partiallyClonedTable = CreatePartiallyСlonedTable(table, row.Index, 1);
        Unit partiallyClonedTableHeight = CalculateTablesHeight(pageAndStylesConfig, [partiallyClonedTable], BordersRenderOption.WithoutTopAndBottom);

        return partiallyClonedTableHeight;
    }
    public static Unit CalculateTablesHeight(Action<Document> pageAndStylesConfig, IEnumerable<Table> tables, BordersRenderOption bordersRenderOption)
    {
        var document = new Document();
        var section = document.AddSection();
        pageAndStylesConfig(document);

        foreach (var table in tables)
        {
            Table newTable = table.Clone();
            if (bordersRenderOption == BordersRenderOption.WithoutTopAndBottom)
            {
                newTable.Borders.Top.Clear();
                newTable.Borders.Bottom.Clear();
            }
            section.Add(newTable);
        }

        Unit occupiedHeight = CalculateTablesHeightFromRender(document);
        return occupiedHeight;
    }

    private static Unit CalculateTablesHeightFromRender(Document document)
    {
        Unit occupiedHeight = Unit.Zero;
        var renderer = new DocumentRenderer(document);
        renderer.PrepareDocument();
        DocumentObject[] documentobjects = renderer.GetDocumentObjectsFromPage(1);
        RenderInfo[]? info = renderer.GetRenderInfoFromPage(1);
        if (info == null) throw new NullReferenceException();
        for (int i = 0; i < documentobjects.Length; i++)
        {
            if (documentobjects[i] is Table)
            {
                var tableinfo = (MigraDoc.Rendering.TableRenderInfo)info[i];
                occupiedHeight += Unit.FromPoint(tableinfo.LayoutInfo.ContentArea.Height.Point);
            }
        }

        return occupiedHeight;
    }
    private static Table CreatePartiallyСlonedTable(Table inputTable, int startingRowIndex, int numberOfRowsToClone)
    {
        Table outputTable = new Table();
        outputTable.Columns = inputTable.Columns.Clone();
        if (numberOfRowsToClone < 0)
            throw new ArgumentOutOfRangeException("The number of rows to clone must be greater than 0.");
        if (startingRowIndex < 0)
            throw new ArgumentOutOfRangeException("The row index must not be negative.");
        int currentRowIndex = startingRowIndex;
        int remainingRowsNumber = numberOfRowsToClone;
        while (remainingRowsNumber > 0)
        {
            var row = outputTable.AddRow();
            row.Cells = inputTable.Rows[currentRowIndex].Cells.Clone();
            remainingRowsNumber --;
            currentRowIndex ++;
        }
        return outputTable;
    }
}

    // table creation code somewhere...
    row3.Cells[1].MergeDown = 3;

    // after all the table creation code
    Cell cellB3 = row3.Cells[1];
    MigraDocHelper.MergedCellHeightFix(document => PageAndStyleConfig(document), cellB3);

    // Your document must be configured with exactly the same config that you pass to the fix.
    private void PageAndStyleConfig(Document document)
    {
        var section = document.LastSection;
        var pageSetup = new PageSetup
        {
            PageFormat = PageFormat.A4,
            SectionStart = BreakType.BreakNextPage,
            Orientation = Orientation.Landscape,
            PageWidth = "29.7cm",
            PageHeight = "21cm",
            TopMargin = Unit.FromMillimeter(6),
            BottomMargin = Unit.FromMillimeter(6),
            LeftMargin = Unit.FromMillimeter(10),
            RightMargin = Unit.FromMillimeter(10),
            HeaderDistance = Unit.FromMillimeter(0),
            FooterDistance = Unit.FromMillimeter(0),
            OddAndEvenPagesHeaderFooter = false,
            DifferentFirstPageHeaderFooter = true,
            MirrorMargins = false,
            HorizontalPageBreak = false,
            StartingNumber = 1
        };
        section.PageSetup = pageSetup;

        var style = document.Styles[StyleNames.Normal]!;
        style.Font.Name = "Times New Roman";
        style.Font.Size = 10;

        style = document.Styles.AddStyle(MyCellStyle, StyleNames.Normal);
        style.Font.Name = "Times New Roman";
        style.Font.Size = 12;
        style.ParagraphFormat.Alignment = ParagraphAlignment.Center;
    }