fix: fix template export generating corrupted Excel files #917

A-nony-mous · 2026-01-23T21:13:44Z

Description

This PR addresses a bug where Excel files generated from templates could become corrupted or throw an "XML error" upon opening.

Problem

When using MiniExcel.SaveAsByTemplate() with Excel templates containing SharedStrings, the generated files would fail to open in Excel with the error "We found a problem with some content in 'xxx.xlsx'".

template:
GachaLog.xlsx

demo error file:
1.xslx

logic code:

    private async Task ExportAsExcelAsync(long uid, string output)
    {
        using var dapper = DatabaseService.CreateConnection();
        var list = GetGachaLogItemEx(uid);
        var template = Path.Combine(AppContext.BaseDirectory, @"Assets\Template\GachaLog.xlsx");
        if (File.Exists(template))
        {
            await MiniExcel.SaveAsByTemplateAsync(output, template, new { list });
        }
    }

Root Causes

Invalid cell type for SharedStrings: The code was setting t="str" with <v> element, but OpenXML requires t="inlineStr" with <is><t>...</t></is> structure for inline strings.
Incorrect XML element order: Elements were written in wrong order. Per ECMA-376 specification, the correct order after </sheetData> must be: autoFilter → mergeCells → phoneticPr → conditionalFormatting.
Duplicate namespace declarations: phoneticPr, conditionalFormatting, and autoFilter elements contained redundant xmlns="..." declarations when written to the output.
Number cells with wrong type attribute: Numeric cells were incorrectly getting t="inlineStr" attribute, which should be omitted for numbers.

Related Issue

issue1
issue2

Changes

ReplaceSharedStringsToStr: Convert SharedString references to proper inlineStr format with <is><t> structure
New SetCellType method: Centralized cell type handling - uses inlineStr for strings, removes t attribute for numbers
WriteSheetXmlAsync: Fixed element order per ECMA-376 spec, extract and rewrite autoFilter in correct position
CleanXml: Added cleanup for xmlns="..." declarations
GenerateCellValuesAsync: Clean up empty <v></v> tags, support <is><t> structure in value lookup

Testing

Tested with template containing 3650 rows of data
Generated file opens successfully in Microsoft Excel without repair prompts
Verified XML structure compliance with ECMA-376 specification

Breaking Changes

None. These are bug fixes that produce valid OpenXML output.

gemini-code-assist · 2026-01-23T21:14:01Z

Summary of Changes

Hello @A-nony-mous, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves critical issues causing Excel files generated from templates to become corrupted or unreadable. The changes primarily focus on correcting the OpenXML structure, cell type handling, and XML element ordering to strictly comply with the ECMA-376 specification, thereby ensuring the reliability and integrity of exported Excel documents.

Highlights

XML Structure Compliance: Reordered XML elements (autoFilter, mergeCells, phoneticPr, conditionalFormatting) in WriteSheetXmlAsync to adhere to ECMA-376 specification, preventing file corruption.
Shared String Handling: Converted SharedString references to the correct inlineStr format (...) and introduced a SetCellType method for consistent cell type management.
XML Cleanup and Validation: Implemented CleanXml to remove redundant namespace declarations and GenerateCellValuesAsync to clean up empty tags, ensuring valid OpenXML output.
Numeric Cell Type Correction: Ensured numeric cells no longer incorrectly receive t="inlineStr" attributes, with the t attribute now being omitted for numbers as per spec.

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gemini-code-assist

Code Review

This pull request provides a comprehensive fix for a bug causing corrupted Excel file generation from templates. The changes correctly address multiple root causes related to OpenXML specification compliance, including element ordering, cell type representation for strings, and handling of shared strings. The introduction of the SetCellType method is an excellent refactoring that centralizes and standardizes cell type management. The code is well-structured, and the fixes are thorough. I have a couple of suggestions to further improve robustness and code style.

src/MiniExcel.Core/OpenXml/Templates/OpenXmlTemplate.Impl.cs

gemini-code-assist · 2026-01-23T21:15:49Z

src/MiniExcel.Core/OpenXml/Templates/OpenXmlTemplate.Impl.cs

+            if (type == "b")
+                 c.SetAttribute("t", "b");
+            else
+                 c.RemoveAttribute("t"); 


For consistency with the rest of the file and to prevent potential bugs, it's recommended to use braces {} for if-else blocks, even for single-line statements. The indentation is also inconsistent here.

if (type == "b") { c.SetAttribute("t", "b"); } else { c.RemoveAttribute("t"); }

- Change SharedString conversion to use inlineStr format with <is><t> structure - Add SetCellType method to properly handle cell types (inlineStr for strings, remove t attr for numbers) - Fix XML element order per ECMA-376 spec (autoFilter before mergeCells/phoneticPr) - Clean duplicate xmlns declarations from phoneticPr, conditionalFormatting, autoFilter - Remove empty <v></v> tags that cause invalid XML - Support <is><t> structure in value node lookup Fixes template SaveAs generating files that Excel cannot open

michelebastione · 2026-01-25T18:21:35Z

Hello @A-nony-mous, we appreciate your contribution. Unfortunately 8 tests are failing after your modifications, so until you investigate why that happens and fix it this PR cannot be accepted.

…cel export

…l export

A-nony-mous · 2026-01-25T20:14:49Z

@michelebastione I am sorry for previous bugs I made and I have fixed them.

Besides, I updated

MiniExcel/tests/MiniExcel.Core.Tests/MiniExcelIssueTests.cs

Lines 1033 to 1047 in 5cfa15b

    
           public void TestIssueI4DQUN() 
        
           { 
        
               var templatePath = PathHelper.GetFile("xlsx/TestIssueI4DQUN.xlsx"); 
        
               using var path = AutoDeletingPath.Create(); 
        
               var value = new Dictionary<string, object> 
        
               { 
        
                   { "Title", "Hello & World < , > , \" , '" }, 
        
                   { "Details", new[] { new { Value = "Hello & Value < , > , \" , '" } } }, 
        
               }; 
        
                _excelTemplater.ApplyTemplate(path.ToString(), templatePath, value); 
        
               var sheetXml = SheetHelper.GetZipFileContent(path.ToString(), "xl/worksheets/sheet1.xml"); 
        
               Assert.Contains("<v>Hello &amp; World &lt; , &gt; , \" , '</v>", sheetXml); 
        
               Assert.Contains("<v>Hello &amp; Value &lt; , &gt; , \" , '</v>", sheetXml); 
        
           }

Since this PR changes the output format of string cells from SharedString-like [<v>] tags to InlineString [<is><t>] tags (to satisfy ECMA-376 and avoid corruption), the assertion in this test needed to be updated to verify the new [<t>] tag format instead of the old [<v>] tag.

I've verified that all tests passed locally.

Green text shows "Successful" in Chinese.

I will leave this as a draft for your review. If you are happy with this please let me know and make it ready for another test?

A-nony-mous · 2026-01-25T20:15:36Z

/gemini review

gemini-code-assist

Code Review

This pull request provides a comprehensive fix for a bug causing corrupted Excel file generation from templates. The changes are well-structured and address multiple root causes, including incorrect XML element order, invalid cell types for shared strings, and redundant namespace declarations. The introduction of the SetCellType method is a great refactoring for centralizing cell type handling. I've added a few suggestions to further improve code robustness and maintainability.

src/MiniExcel.Core/OpenXml/Templates/OpenXmlTemplate.Impl.cs

Fixing potential bug with inline string tag not being correctly identified when <v> tag is not null but also not matching the regex condition, and added GeneratedRegexAttribute for optimizing empty <v> tag regex replace function

michelebastione · 2026-01-25T23:06:32Z

Looks good, I just want to make a couple more checks but I'll probably merge it tomorrow.

gemini-code-assist bot reviewed Jan 23, 2026

View reviewed changes

A-nony-mous force-pushed the fix/ReplaceSharedStringsToStr branch from c49d438 to 7eb1196 Compare January 23, 2026 21:19

A-nony-mous mentioned this pull request Jan 23, 2026

fix: fix export excel Scighost/Starward#1737

Open

michelebastione marked this pull request as draft January 25, 2026 18:21

A-nony-mous added 3 commits January 26, 2026 03:54

fix: handle inline string cells and preserve namespace prefixes in Ex…

aeb5f0e

…cel export

fix: ensure text is not null when processing XML nodes in Excel export

58c35de

fix: update template to use inlineStr format for string cells in Exce…

e9c1251

…l export

gemini-code-assist bot reviewed Jan 25, 2026

View reviewed changes

Couple of fixes

24eb49a

Fixing potential bug with inline string tag not being correctly identified when <v> tag is not null but also not matching the regex condition, and added GeneratedRegexAttribute for optimizing empty <v> tag regex replace function

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A-nony-mous commented Jan 23, 2026

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