ErrorApi 1.0.1 

dotnet add package ErrorApi --version 1.0.1
                    


                    

                
NuGet\Install-Package ErrorApi -Version 1.0.1
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="ErrorApi" Version="1.0.1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package. 
<PackageVersion Include="ErrorApi" Version="1.0.1" />
                    


                            Directory.Packages.props
                        

                    

                
<PackageReference Include="ErrorApi" />
                    


                            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 ErrorApi --version 1.0.1
                    


                    

                
#r "nuget: ErrorApi, 1.0.1"
#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 ErrorApi@1.0.1
#: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=ErrorApi&version=1.0.1
                    


                            Install as a Cake Addin
                        

                    

                
#tool nuget:?package=ErrorApi&version=1.0.1
                    


                            Install as a Cake Tool

ErrorApi

ErrorApi

Start here. One package: the source generator, the Error/Result primitives and the ASP.NET Core integration — so the OpenAPI document lists every failure each endpoint can actually return, and the response body always matches it.

dotnet add package ErrorApi

That is the whole install. This is a meta-package: it carries no code of its own, only ErrorApi.AspNetCore (which ships the generator and the primitives) — and on .NET 8/9 also ErrorApi.Swashbuckle, because there the document has to come through Swagger.

Quickstart

1. Declare the catalog — the class declares membership and the default status, the members declare the names; the generator writes the bodies and infers the codes:

[ErrorCatalog("Orders", StatusCodes.Status404NotFound)]
public static partial class OrderErrors
{
    public static partial Error NotFound { get; }                              // Orders.NotFound, 404

    [Error(StatusCodes.Status409Conflict, Detail = "Order {0} was already paid.")]
    public static partial Error AlreadyPaid(Guid orderId);                     // Orders.AlreadyPaid, 409
}

2. Return the entries — Error converts implicitly into Result<T>:

public Result<Order> GetById(Guid id) =>
    _orders.TryGetValue(id, out var order) ? order : OrderErrors.NotFound;

3. Wire it up once — AddErrorApi() is the whole minimal setup:

builder.Services.AddOpenApi();
builder.Services.AddErrorApi();

app.MapGet("/orders/{id:guid}", (Guid id, IOrderService s) => s.GetById(id).ToHttpResult());

On .NET 8/9 swap the first line for Swagger — the filter is already in the box:

builder.Services.AddSwaggerGen(c => c.AddErrorApiResponses());
builder.Services.AddErrorApi();

One more thing there: partial properties like NotFound above are a C# 13 feature, so a net8/net9 project sets <LangVersion>latest</LangVersion> — or declares its entries as partial methods, which every C# the packages support can compile.

The generator walks each handler through the call graph, works out which catalog entries it can reach, and emits a reflection-free model. The document gains one response per status with every reachable code listed and an example problem body; at runtime the same model maps each failure to application/problem+json carrying that code — native-AOT clean, nothing decided on the request path.

When to reach past this package

Package Take it when
ErrorApi.Abstractions a class library only declares catalog entries — attributes and primitives, no ASP.NET Core
ErrorApi.AspNetCore you want exactly the integration and nothing else picking dependencies for you
ErrorApi.Swashbuckle a .NET 10 project stays on Swagger (on net8/net9 this package already brings it)
ErrorApi.ErrorOr, .OneOf, .LanguageExt, .FluentResults, .ArdalisResult, .CSharpFunctionalExtensions you already use that result library — keep your types, often a bare [Error] is the entire onboarding

Full documentation

github.com/SideswipeN7/ErrorApi — how discovery works, the EAPI001–EAPI013 diagnostics, the TypeScript error contract, and the result-library adapters.

There are no supported framework assets in this package.

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NuGet packages

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Version Downloads Last Updated
1.0.1 86 8/31/2026