FirstClassErrors 0.1.0-preview.1

.NET Standard 2.0 This package targets .NET Standard 2.0. The package is compatible with this framework or higher.
This is a prerelease version of FirstClassErrors. 
dotnet add package FirstClassErrors --version 0.1.0-preview.1
                    


                    

                
NuGet\Install-Package FirstClassErrors -Version 0.1.0-preview.1
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package. 
<PackageReference Include="FirstClassErrors" Version="0.1.0-preview.1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
<PackageVersion Include="FirstClassErrors" Version="0.1.0-preview.1" />
                    


                            Directory.Packages.props
                        

                    

                
<PackageReference Include="FirstClassErrors" />
                    


                            Project file
For projects that support Central Package Management (CPM), copy this XML node into the solution Directory.Packages.props file to version the package. 
paket add FirstClassErrors --version 0.1.0-preview.1
                    


                    

                
#r "nuget: FirstClassErrors, 0.1.0-preview.1"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package. 
#:package FirstClassErrors@0.1.0-preview.1
#:package directive can be used in C# file-based apps starting in .NET 10 preview 4. Copy this into a .cs file before any lines of code to reference the package. 
#addin nuget:?package=FirstClassErrors&version=0.1.0-preview.1&prerelease
                    


                            Install as a Cake Addin
                        

                    

                
#tool nuget:?package=FirstClassErrors&version=0.1.0-preview.1&prerelease
                    


                            Install as a Cake Tool

FirstClassErrors

FirstClassErrors is a lightweight .NET library that turns exceptions into structured, documented, and diagnosable errors.

Instead of throwing ad-hoc messages, the library helps you define errors as explicit concepts with diagnostics and documentation directly in code.

It is especially useful for systems where supportability, troubleshooting, and operational clarity matter.

Key ideas

FirstClassErrors allows you to:

  • define structured errors with stable error codes
  • attach diagnostics and investigation leads
  • keep error documentation close to the code
  • generate human-readable documentation automatically

Errors become documented knowledge about your system, not just runtime failures.

Example

return DescribeError.WithTitle("Temperature below absolute zero")
                    .WithDescription("This error occurs when trying to instantiate a temperature with a value that is below absolute zero.")
                    .WithRule("Temperature cannot go below absolute zero because absolute zero is the point where particles have minimum possible energy.")
                    .WithDiagnostics(ValueObjectDiagnostic.Diagnostic)
                    .WithExamples(
                        () => BelowAbsoluteZero(-1, TemperatureUnit.Kelvin),
                        () => BelowAbsoluteZero(-280, TemperatureUnit.Celsius));

This produces structured documentation tied directly to the error definition.

When to use FirstClassErrors

This library is particularly useful when:

  • building complex business systems
  • designing domain-driven models
  • improving error observability
  • supporting production troubleshooting
  • generating living documentation from code

Documentation

Full documentation and guides are available on GitHub:

https://github.com/Reefact/first-class-errors

Product Compatible and additional computed target framework versions.
.NET net5.0 was computed.  net5.0-windows was computed.  net6.0 was computed.  net6.0-android was computed.  net6.0-ios was computed.  net6.0-maccatalyst was computed.  net6.0-macos was computed.  net6.0-tvos was computed.  net6.0-windows was computed.  net7.0 was computed.  net7.0-android was computed.  net7.0-ios was computed.  net7.0-maccatalyst was computed.  net7.0-macos was computed.  net7.0-tvos was computed.  net7.0-windows was computed.  net8.0 was computed.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed.  net9.0 was computed.  net9.0-android was computed.  net9.0-browser was computed.  net9.0-ios was computed.  net9.0-maccatalyst was computed.  net9.0-macos was computed.  net9.0-tvos was computed.  net9.0-windows was computed.  net10.0 was computed.  net10.0-android was computed.  net10.0-browser was computed.  net10.0-ios was computed.  net10.0-maccatalyst was computed.  net10.0-macos was computed.  net10.0-tvos was computed.  net10.0-windows was computed. 
.NET Core netcoreapp2.0 was computed.  netcoreapp2.1 was computed.  netcoreapp2.2 was computed.  netcoreapp3.0 was computed.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.0 is compatible.  netstandard2.1 was computed. 
.NET Framework net461 was computed.  net462 was computed.  net463 was computed.  net47 was computed.  net471 was computed.  net472 was computed.  net48 was computed.  net481 was computed. 
MonoAndroid monoandroid was computed. 
MonoMac monomac was computed. 
MonoTouch monotouch was computed. 
Tizen tizen40 was computed.  tizen60 was computed. 
Xamarin.iOS xamarinios was computed. 
Xamarin.Mac xamarinmac was computed. 
Xamarin.TVOS xamarintvos was computed. 
Xamarin.WatchOS xamarinwatchos was computed. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

  • .NETStandard 2.0

    • No dependencies.

NuGet packages (1)

Showing the top 1 NuGet packages that depend on FirstClassErrors:

Package Downloads
FirstClassErrors.Testing

Testing helpers for FirstClassErrors: fluent, framework-agnostic assertions on Outcome and Error, plus a freezable clock and instance ids so an error's OccurredAt and InstanceId become deterministic in your tests.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last Updated
0.1.0-preview.1 212 7/12/2026

Initial preview release of FirstClassErrors.