Johan Appelgren
Software Engineer at Macrobond Financial
Greater Gothenburg Metropolitan Area Sweden
Summary
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Rockstar🎓
Top SchoolJohan Appelgren is a seasoned software engineer with 13 years of professional experience, currently building financial software at Macrobond Financial from his base in Greater Gothenburg. He holds an M.Sc. in Software Engineering from Chalmers and brings a strong backend focus cultivated since early roles at Vinga System AB. Johan contributes to open-source tooling for real-world data problems — notably improving robustness in the popular ExcelDataReader C# library by fixing edge cases around indexing, Unicode formats and label records. His work shows attention to obscure but critical file-format edge cases, reflecting a pragmatic, test-driven approach to reliability. Colleagues rely on him for steady, detail-oriented engineering that keeps data pipelines sane in production.
13 years of coding experience
4 years of employment as a software developer
Master of Science in Engineering, Software Engineering, Master of Science in Engineering, Software Engineering at Chalmers University of Technology
Swedish, English
Stackoverflow
341reputation
12kreached
8answers
0questions
Github Skills (15)
net10
asp-net10
xlsx10
dotnet10
csharp10
excel10
dotnet-core10
xls10
exceldatareader6
wpf6
android6
silverlight6
geolocation6
cordova6
background-process6
Programming languages (4)
Github contributions (5)
ExcelDataReader/ExcelDataReader
Jul 2016 - Dec 2022
Lightweight and fast library written in C# for reading Microsoft Excel files
Role in this project:
Back-end Developer
Back-end DeveloperContributions:6 releases, 1 review, 125 commits in 6 years 6 months
Contributions summary:Johan added a failing test and made several code changes related to handling Excel files. These changes specifically addressed scenarios where Excel files had no index or row records and were critical for the functionality of the Excel data reader library. Further, they modified existing code to account for extended Unicode formatting strings, corrected how label records are read, and implemented features to handle edge cases, improving the robustness of the library.
xlsxdotnetxlsopenxmlxlsb
appel1/ExcelDataReader
Jul 2016 - Mar 2021
Lightweight and fast library written in C# for reading Microsoft Excel files
Contributions:73 pushes, 74 branches in 4 years 9 months
xlsxxlsopenxmlmicrosoft-excelcsharp
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