ResultTypes

Result types for .NET Core including extensions for automatic handling in ASP.NET Core and MediatR.

Basic usage

Void value Result:

internal class MyCommandHandler : IRequestHandler<MyCommand, Result>
{
	public async Task<Result> Handle(MyCommand request)
	{
		// do some work

		return Result.Success();
	}
}

Result with Value:

internal class MyCommandHandler : IRequestHandler<MyCommand, Result<MyResponse>>
{
	public async Task<Result<MyResponse>> Handle(MyCommand request)
	{
		MyResponse response;

		// do some work

		return Result.Success(response);
	}
}

Invalid request:

internal class MyCommandHandler : IRequestHandler<MyCommand, Result>
{
	public async Task<Result> Handle(MyCommand request)
	{
		if (!request.IsValid())
		{
			return Result.Invalid(new ValidationResult("The request is not valid"));
		}
		
		// do some work

		return Result.Success();
	}
}

Not found result:

internal class MyCommandHandler(IMyRepository repo) : IRequestHandler<MyCommand, Result<Entity>>
{
	public async Task<Result<Entity>> Handle(MyCommand request)
	{
		var entity = await repo.Get(request.Id);

		return entity switch
		{
			null => Result.NotFound(),
			_ => Result.Success(entity)
		};
	}
}

Error result:

internal class MyCommandHandler(IMyRepository repo) : IRequestHandler<MyCommand, Result<Entity>>
{
	public async Task<Result<Entity>> Handle(MyCommand request)
	{
		try
		{
			var entity = await repo.Get(request.Id);

			return Result.Success(entity)
		}
		catch (Exception ex)
		{
			return Result.Error(ex);
		}
	}
}

Ensure success

Throw if Status is not Success

internal class MyCommandHandler(IMediator mediator) : IRequestHandler<MyCommand, Result>
{
	public async Task<Result> Handle(MyCommand request)
	{
		var queryResult = await mediator.Send(new GetEntityByIdQuery(request.Id));

 		// throws appropriate Exception if queryResult.IsSuccess is false
		// the Exceptions can be automatically handled by ResultTypes.Extensions.MediatR
		queryResult.EnsureSuccess();

		// do some work

		return Result.Success();
	}
}

Throw if result has no value

internal class MyCommandHandler(IMediator mediator) : IRequestHandler<MyCommand, Result>
{
	public async Task<Result> Handle(MyCommand request)
	{
		var queryResult = await mediator.Send(new GetEntityByIdQuery(request.Id));

		Entity entity;
		entity = queryResult.Value; // might be null

 		// throws appropriate Exception if queryResult.HasValue is false
		// the Exceptions can be automatically handled by ResultTypes.Extensions.MediatR
		queryResult.EnsureValue();

		entity = queryResult.Value; // will be not null

		// do some work

		return Result.Success();
	}
}

Automatic conversion

Implicit success result:

internal class MyCommandHandler : IRequestHandler<MyCommand, Result<MyResponse>>
{
	public async Task<Result<MyResponse>> Handle(MyCommand request)
	{
		MyResponse response;

		// do some work

		return response;
	}
}

ASP.NET Core integration

Use instead of Microsoft.AspNetCore.Http.TypedResult:

public static class Endpoints
{
    public static void MapGetEntity(this IEndpointRouteBuilder app)
    {
        app.MapGet("/{id:guid}", GetEntity);
    }

    public static async Task<ResultType.Ok<Entity>> GetEntity([FromServices] IMediator mediator, [FromRoute] Guid id)
    {
        return await mediator.Send(new GetEntityQuery(id));
    }
}

Returning any ResultType will automatically the API Explorer and therefore swagger with the correct return type and status codes.

The Result will be implicitly converted to ResultTypes.Extensions.AspNetCore.ResultType.

MediatR integration

Register request exception handler:

using ResultTypes.Extensions.MediatR;

public static class ServiceCollectionExtensions
{
	public static IServiceCollection AddServices(this IServiceCollection services)
	{
		services.AddResultMediatRExceptionHandler();

		return services;
	}
}

If the response is a Result, the exception handler will map exceptions of type ValidationException to Result.Invalid and all other exceptions to Result.Error. Exceptions thrown by Result.EnsureSuccess and Result.EnsureValue will be mapped back to the original Result type.