BorderAround() silently drops the Bottom (and sometimes Right) border side in EPPlus 8.x

[devguyky]

EPPlus usage

Commercial use (I have a commercial license)

Environment

Windows 11, .NET 10

Epplus version

Regression present in 8.0.1 through 8.7.0 (latest tested). Confirmed working correctly in 7.7.3.

Spreadsheet application

Microsoft Excel

Description

Description

ExcelRangeBase.Style.Border.BorderAround(style) no longer reliably writes the Bottom border side (and inconsistently the Right side) to the workbook's styles.xml when called on individual cells in a loop. This results in missing bottom borders on printed/exported sheets — most noticeably on the last row of a bordered table, since internal rows visually "borrow" a border from the adjacent row's Top edge, but the final row has nothing below it to compensate.

This worked correctly in EPPlus 7.7.3 and regressed sometime before/at 8.0.1. It does not appear to be listed on the Breaking Changes in EPPlus 8 wiki page. It may be a side effect of the change made for #736 (connecting-cell border override), but the resulting behavior here is not a "widest border wins" cosmetic difference — the Bottom side is dropped from the XML entirely.

Workaround

Set each side explicitly instead of calling BorderAround():

cell.Style.Border.Top.Style = style;
cell.Style.Border.Bottom.Style = style;
cell.Style.Border.Left.Style = style;
cell.Style.Border.Right.Style = style;

This produces the correct 4-sided border XML in 8.7.0.

[JanKallman]

Thanks! We'll have a look at this.

[OssianEPPlus]

We're having trouble re-producing your issue. Even when applying it on the last row of a table the bottom row appears to be set correctly.
Inn e.g. the following example it seems to work:

using (var package = new ExcelPackage("i2525.xlsx"))
{
    var ws = package.Workbook.Worksheets.Add("BorderAround_MissingStyles");

    var tb1 = ws.Tables.Add(ws.Cells["B2:K11"], "BorderedTable");
    //TableStyles.Light15 has borders on every cell making this a "bordered table"
    tb1.TableStyle = OfficeOpenXml.Table.TableStyles.Light15;

    for (int i = 0; i < 10; i++)
    {
        for (int j = 0; j < 10; j++)
        {
            //Set borders on every "even" individual cell
            if (j % 2 > 0 && i % 2 > 0)
            {
                ws.Cells[i + 2, j + 2].Style.Border.BorderAround(OfficeOpenXml.Style.ExcelBorderStyle.Dashed);
            }
        }
    }

    //Save workbook
}

It's possible your case is slightly different, like applying a border via the ".TableBorder" property or applying a "Show Total" to the table or any number of other possible factors that set the border styling information in some way. We've attempted several of these variations but none of them seem to reproduce your issue.

Please provide us with a Minimal Reproducible Sample either by editing this example or providing your own.

[devguyky]

Thanks for taking a look! We narrowed it down further — the missing border becomes visibly manifest specifically when the adjacent cell that "owns" the shared border is hidden or lands on a different printed page (page break).

Minimal repro

using OfficeOpenXml;
using OfficeOpenXml.Style;

ExcelPackage.License.SetNonCommercialPersonal("Test");

using var package = new ExcelPackage();
var ws = package.Workbook.Worksheets.Add("Sheet1");

for (int c = 0; c < 4; c++)
{
    var cell = ws.Cells[1, c + 1];
    cell.Value = $"C{c}";
    cell.Style.Border.BorderAround(ExcelBorderStyle.Thin);
}

// Hide the 3rd column
ws.Column(3).Hidden = true;

package.SaveAs(new FileInfo(@"C:\temp\hiddencol.xlsx"));

Resulting xl/styles.xml

<border><left style="thin"/><right/><top style="thin"/><bottom style="thin"/><diagonal/></border>   <!-- used by columns A, B, C -->
<border><left style="thin"/><right style="thin"/><top style="thin"/><bottom style="thin"/><diagonal/></border>  <!-- used by column D -->

Column B (visible) has its Right border stripped — presumably because EPPlus assumes the neighboring column C will supply the shared edge via its own Left border. But column C is hidden, so nothing renders there.

Net effect: no border anywhere between visible columns B and D — a real, visible gap in the printed output / PDF export, exactly at the seam where the hidden column collapses.

Why this matches our page-wrap reports too

We believe the same failure mode explains the page-wrap case: when a bordered table spans a print page break, the row/column expected to supply "the other half" of a shared border ends up on a different page, so the border silently disappears at the page seam — same underlying cause, just triggered by pagination instead of a hidden column.

[OssianEPPlus]

You may wish to "visibly manifest" or rather, verify that example with your own eyes.
When running the example you have supplied, the resulting file in Excel, looks entirely correct
When inspecting the .xml files themselves the border-Right styling does appear to be removed from the xml which could implicate a bug but actually inspecting the file shows that there is no visual difference.

After reviewing further it is clear that this section:

// Hide the 3rd column
ws.Column(3).Hidden = true;

Does nothing to actually cause the bug. (Meaning this is technically not a minimal repro) This as removing the line from the code results in the same output xml in "xl/styles.xml".

As far as we can see this is intended behaviour, here's why:

When setting the borders of e.g. The cell "C1" Epplus assumes that this most recent change should override other border settings. And will therefore remove the border settings of B1.Border.Right and D1.Border.Left.
In your example the only reason D1.Border.Left is not removed as well is because it is set After the "C1" cell.
You can avoid the overriding default by setting the overrideNeigbourCellBorder parameter to false:

//You can change this line to not overrride other border settings like so:
cell.Style.Border.BorderAround(ExcelBorderStyle.Thin, false);

One could argue it should Set the Right border of the previous cell rather than delete its setting but this causes issues when a neighbouring cell's border is thicker as that "wins" in Excel's view.

We even went as far as to Print the result of your example as you mentioned it possibly being related to page-wrap. Even when doing so there is no apparent issue. We have no doubt that you're experiencing an issue and possibly a bug but what you have provided does not reproduce it. Such things can be avoided and we ask that you please try to verify the sample code and its output yourself before you send it to us. It would save both yourself and us some valuable effort and time.

[OssianEPPlus]

Does that settle the matter? Or do you have a new case that can generate a reproducible bug?