CSharpFunctionalExtensions.HttpResults

Extensions for CSharpFunctionalExtensions to map Results to HttpResults in your MinimalApi

Installation

Available on NuGet.

dotnet add package CSharpFunctionalExtensions.HttpResults

or

PM> Install-Package CSharpFunctionalExtensions.HttpResults

Usage

This library provides you extension methods to map the following types to HttpResults:

• Result
• Result<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

For almost every method you can override the default status codes for Success/Failure.

All methods are available in sync and async variants.

By default, failures get mapped to a ProblemHttpResult based on RFC9457. The status property contains the status code. The type property contains a URI to the corresponding RFC9110 entry based on the status code. The title property contains a generic short messages based on the status code. The detail property contains the error property of the Result.

If you want your own mapping logic read on.

Custom errors

This library uses a Source Generator to generate extension methods for your own custom error types when using Result<T,E> or UnitResult<E>.

1. First create a custom error type

   public class UserNotFoundError
   {
       public required string UserId { get; init; }
   }

2. Create a mapper that implements IResultErrorMapper which maps this custom error type to an IResult that you want to return in your WebAPI:

   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);  
       };
   }

3. Use the generated extension method:

   app.MapGet("/users/{id}", (string id) => {
       return userRepository.Find(id) //Result<User,UserNotFoundError>
           .ToOkHttpResult(); //returns 200 with User as payload or 404 with ProblemDetails object defined above
   });

Make sure that every custom error type has exactly one corresponding IResultMapper implementation. Otherwise, the build might fail with diagnostic error CFEHTTPR002.

If extension methods for custom errors are missing, rebuild the project to trigger Source Generation.

Optionally, there is a helper method ProblemDetailsMap.Find() to find a suitable title and type for a status code based on RFC9110.