Seamlessly map Results from CSharpFunctionalExtensions to HttpResults for cleaner, more fluent Web APIs
$ dotnet add package CSharpFunctionalExtensions.HttpResultsExtensions for CSharpFunctionalExtensions to map Results to HttpResults in your Web-API
This library streamlines returning HttpResults from endpoints that leverage CSharpFunctionalExtensions by offering convenient extension methods to map you result to an HttpResult. With these, you can maintain a fluent, railway-oriented style by simply invoking the appropriate method at the end of your result chain. It also supports custom error types and ensures a clear separation between your domain logic and API by using specific mappers to translate domain details into API responses.
Available on NuGet.
dotnet add package CSharpFunctionalExtensions.HttpResultsor
PM> Install-Package CSharpFunctionalExtensions.HttpResultsThis library provides you extension methods to map the following Result types to HttpResults:
ResultResult<T>Result<T,E>UnitResult<E>These methods are available:
| Method | Short Description |
|---|---|
.ToStatusCodeHttpResult() | Returns StatusCodeHttpResult or ProblemHttpResult |
.ToStatusCodeHttpResult<T>() | Returns StatusCodeHttpResult or ProblemHttpResult |
.ToStatusCodeHttpResult<T,E>() | Returns StatusCodeHttpResult or custom error |
.ToStatusCodeHttpResult<E>() | Returns StatusCodeHttpResult or custom error |
.ToJsonHttpResult<T>() | Returns JsonHttpResult<T> or ProblemHttpResult |
.ToJsonHttpResult<T,E>() | Returns JsonHttpResult<T> or custom error |
.ToOkHttpResult<T>() | Returns Ok<T> or ProblemHttpResult |
.ToOkHttpResult<T,E>() | Returns Ok<T> or custom error |
.ToNoContentHttpResult() | Returns NoContent or ProblemHttpResult |
.ToNoContentHttpResult<T>() | Discards value of Result<T> and returns NoContent or ProblemHttpResult |
.ToNoContentHttpResult<T,E>() | Discards value of Result<T> and returns NoContent or custom error |
.ToNoContentHttpResult<E>() | Returns NoContent or custom error |
.ToCreatedHttpResult<T>() | Returns Created<T> or ProblemHttpResult |
.ToCreatedHttpResult<T,E>() | Returns Created<T> or custom error |
.ToCreatedAtRouteHttpResult<T>() | Returns CreatedAtRoute<T> or ProblemHttpResult |
.ToCreatedAtRouteHttpResult<T,E>() | Returns CreatedAtRoute<T> or custom error |
.ToAcceptedHttpResult<T>() | Returns Accepted<T> or ProblemHttpResult |
.ToAcceptedHttpResult<T,E>() | Returns Accepted<T> or custom error |
.ToAcceptedAtRouteHttpResult<T>() | Returns AcceptedAtRoute<T> or ProblemHttpResult |
.ToAcceptedAtRouteHttpResult<T,E>() | Returns AcceptedAtRoute<T> or custom error |
.ToFileHttpResult<byte[]>() | Returns FileContentHttpResult or ProblemHttpResult |
.ToFileHttpResult<byte[],E>() | Returns FileContentHttpResult or custom error |
.ToFileStreamHttpResult<Stream>() | Returns FileStreamHttpResult or ProblemHttpResult |
.ToFileStreamHttpResult<Stream,E>() | Returns FileStreamHttpResult or custom error |
.ToContentHttpResult<string>() | Returns ContentHttpResult or ProblemHttpResult |
.ToContentHttpResult<string,E>() | Returns ContentHttpResult or custom error |
All methods are available in sync and async variants.
By default, Result and Result<T> failures get mapped to a ProblemHttpResult based on RFC9457.
status property contains the status code of the HTTP response. Note: For almost every method you can override the default status codes for Success/Failure case.type property contains a URI to the corresponding RFC9110 entry based on the status code.title property contains a generic short messages based on the status code.detail property contains the error string of the Result.This default mapping behaviour is configured inside the ProblemDetailsMappingProvider.
You can override this behaviour by providing your own dictionary which maps status code to title and type of the resulting ProblemDetails object.
ProblemDetailsMappingProvider.DefaultMappings = new Dictionary<int, (string? Title, string? Type)>
{
{ 400, ("Ungültige Anfrage", "https://tools.ietf.org/html/rfc9110#section-15.5.1") },
{ 401, ("Nicht autorisiert", "https://tools.ietf.org/html/rfc9110#section-15.5.2") },
{ 403, ("Verboten", "https://tools.ietf.org/html/rfc9110#section-15.5.4") },
{ 404, ("Nicht gefunden", "https://tools.ietf.org/html/rfc9110#section-15.5.5") },
{ 405, ("Methode nicht erlaubt", "https://tools.ietf.org/html/rfc9110#section-15.5.6") },
{ 406, ("Nicht akzeptabel", "https://tools.ietf.org/html/rfc9110#section-15.5.7") },
{ 408, ("Zeitüberschreitung der Anfrage", "https://tools.ietf.org/html/rfc9110#section-15.5.9") },
{ 409, ("Konflikt", "https://tools.ietf.org/html/rfc9110#section-15.5.10") },
{ 412, ("Vorbedingung fehlgeschlagen", "https://tools.ietf.org/html/rfc9110#section-15.5.13") },
{ 415, ("Nicht unterstützter Medientyp", "https://tools.ietf.org/html/rfc9110#section-15.5.16") },
{ 422, ("Nicht verarbeitbare Entität", "https://tools.ietf.org/html/rfc4918#section-11.2") },
{ 426, ("Upgrade erforderlich", "https://tools.ietf.org/html/rfc9110#section-15.5.22") },
{ 500, ("Ein Fehler ist bei der Verarbeitung Ihrer Anfrage aufgetreten.", "https://tools.ietf.org/html/rfc9110#section-15.6.1") },
{ 502, ("Schlechtes Gateway", "https://tools.ietf.org/html/rfc9110#section-15.6.3") },
{ 503, ("Dienst nicht verfügbar", "https://tools.ietf.org/html/rfc9110#section-15.6.4") },
{ 504, ("Gateway-Zeitüberschreitung", "https://tools.ietf.org/html/rfc9110#section-15.6.5") },
};
Example from here
You don't have to provide the whole dictionary but can also override or add only mappings for specific status codes like this:
ProblemDetailsMappingProvider.AddOrUpdateMapping(420, "Enhance Your Calm", "https://http-status-code.de/420/");It's recommended to override the mappings during startup e.g. in Program.cs.
If you need to override the mapping for a specific use case in a single location, you can provide an Action<ProblemDetails> to fully customize the ProblemDetails. This is particularly useful when you want to add extensions or tailor the ProblemDetails specifically for that use case.
Result.Failure<string>(error)
.ToOkHttpResult(customizeProblemDetails: problemDetails =>
{
problemDetails.Title = "Custom Title";
problemDetails.Extensions.Add("custom", "value");
});When using Result<T,E> or UnitResult<E>, this library uses a Source Generator to generate extension methods for your own custom error types.
public record UserNotFoundError(string UserId);
IResultErrorMapper which maps this custom error type to an HttpResult that you want to return in your Web-API:
public class UserNotFoundErrorMapper : IResultErrorMapper<UserNotFoundError, ProblemHttpResult>
{
public Func<UserNotFoundErrorMapper, ProblemHttpResult> Map => error => {
var problemDetails = new ProblemDetails
{
Status = 404,
Title = "User not found",
Type = "https://tools.ietf.org/html/rfc9110#section-15.5.5",
Detail = $"The user with ID {error.UserId} couldn't be found.
};
return TypedResults.Problem(problemDetails);
};
}
app.MapGet("/users/{id}", (string id) => {
return userRepository.Find(id) //Result<User,UserNotFoundError>
.ToOkHttpResult(); //Results<Ok<User>,ProblemHttpResult>
});
[!IMPORTANT]
Make sure that every custom error type has exactly one correspondingIResultMapperimplementation.
You can use the ProblemDetailsMappingProvider.FindMapping() method to find a suitable title and type for a status code based on RFC9110.
[!TIP] If extension methods for custom errors are missing, rebuild the project to trigger Source Generation.
This library includes analyzers to help you use it correctly.
For example, they can notify you if you have multiple mappers for the same custom error type or if you forgot to implement the Map function in your custom error mapper.
You can find a complete list of all analyzers here.
Examples for CRUD, FileStreams, custom errors, etc. in context of a Web-API are available in the CSharpFunctionalExtensions.HttpResults.Examples project.
You're welcome to contribute. Please keep these few rules in mind:
This project uses CSharpier for code formatting. You can format your code with dotnet csharpier ..
To add new methods follow these steps:
Result and Result<T> to CSharpFunctionalExtensions.HttpResults.ResultExtensionsResult<T,E> to CSharpFunctionalExtensions.HttpResults.Generators.ResultExtensions and add the class to ResultExtensionsClassBuilderUnitResult<E> to CSharpFunctionalExtensions.HttpResults.Generators.UnitResultExtensions and add the class to UnitResultExtensionsClassBuilderCSharpFunctionalExtensions.HttpResults.Tests