IronXL: How to Troubleshoot SaveAs() FileNotFoundException in Visual Studio for .NET 10 Projects

Overview

When calling WorkBook.SaveAs() in a .NET 10 project, Visual Studio may surface a FileNotFoundException for IronXL.XmlSerializers. In most cases this is a first-chance exception caught by the debugger, not a real runtime failure — the Excel file is still generated. This article shows you how to confirm which one you are seeing and how to stop the debugger from breaking on it.

Prerequisites

• IronXL.Excel v2026.6.1
• A project targeting .NET 10

Version Metadata

• Minimum Version: N/A
• Superseded-in Version: N/A

Steps

1. Create a new ASP.NET Core Web Application targeting .NET 10 and install IronXL.Excel 2026.6.1.
2. Use a basic workflow: create a workbook, write Hello, World into cell A1, and save the file as .xlsx to your output path.
3. If an exception appears in Visual Studio, check the Just My Code setting under the Visual Studio debugger options. When it is disabled, the debugger breaks immediately on an exception that the library handles internally. Enable it.
4. Verify whether the Excel file was generated successfully. This tells you whether you are looking at an actual runtime failure or a first-chance exception break in the debugger.

Notes

• A first-chance FileNotFoundException related to .NET XML serialization can appear even when file generation succeeds.
• There is no standalone IronXL.XmlSerializers NuGet package to install — do not attempt to add one to resolve the message.