Custom error objects for .Net Core 3 web api

Question

I am currently developing a web api in .NET Core 3. I currently have the following model for my error response object:

public class ErrorRo
{
    public string Message { get; set; }
    public int StatusCode { get; set; }
    public string Endpoint { get; set; }
    public string Parameters { get; set; }
    public string IpAddress { get; set; }
}

This is a mandated response I need to implement, management has pushed this. It allows more verbose error messages for people hitting our API so that they know what went wrong.

At the moment I am currently populating this object manually in the methods themselves. Is there a way where I can overwrite the response methods. I.e. can I override the BadRequest of IActionResult to automatically populate these fields?

Thanks!

There are lots of possible ways to implement this. A custom middleware, Action Filters, a simple static method manually called on responses... — Moha Dehghan
– Moha Dehghan, Commented May 15, 2020 at 9:16
You should look at ActionFilters/ResultFilters. It probably depends one what information you are using to populate said dto. Though it may be easier to make a new controller subclass that has a new OurBadRequest method it and calling that instead — pinkfloydx33
– pinkfloydx33, Commented May 15, 2020 at 9:20

Oleksandr · Accepted Answer · 2021-04-19 12:19:03Z

You can use result filters for this purpose. Add a filter which repalces result before sending it back

Model

public class CustomErroModel
{
    public string Message { get; set; }
    public int StatusCode { get; set; }
    public string Endpoint { get; set; }
    public string Parameters { get; set; }
    public string IpAddress { get; set; }
}

Filter

public class BadRequestCustomErrorFilterAttribute : ResultFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext context)
    {
        //todo: check for BadRequestObjectResult if anything is returned for bad request
        if (context.Result is BadRequestResult) 
        {
            var result = new CustomErroModel
            {
                StatusCode = 200, //you status code
                Endpoint = context.HttpContext.Request.GetDisplayUrl(),
                Message = "some message",
                IpAddress = context.HttpContext.Connection.RemoteIpAddress.ToString(), //find better implementation in case of proxy
                //this returns only parameters that controller expects but not those are not defined in model
                Parameters = string.Join(", ", context.ModelState.Select(v => $"{v.Key}={v.Value.AttemptedValue}"))
            };
            
            context.Result = new OkObjectResult(result); // or any other ObjectResult
        }
    }
}

Then apply filter per action or globally

[BadRequestCustomErrorFilter]
public IActionResult SomeAction(SomeModel model)

or

services
    .AddMvc(options =>
    {
        options.Filters.Add<BadRequestCustomErrorFilterAttribute>();
        //...
    }

devcrp · Accepted Answer · 2020-05-15 09:20:17Z

0

Well it depends on the scenario, but one possible approach could be to use a middleware using a similar strategy like the one described in this question, so that you complete the response with extra information.

answered May 15, 2020 at 9:20

devcrp

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