cartoninjas.net

Starting at asp.net core 2.something, a unified model binding err is return, when input does not bind to an expected model. Api returns 400 with a msg similar to:

{
    "someProperty": [
        "Some error."
    ]
}

There are scenarios however when one may want to return a customised error msg that is used across an application. In order to do this, the following should be done:

Disable the default model validation:

public void ConfigureServices(IServiceCollection services)
{
      //...

      //this should disable the default model validation, so custom attribute can be used instead
      services.Configure<ApiBehaviorOptions>(opts =>
      {
          opts.SuppressModelStateInvalidFilter = true;
      });

      //...
}

Create a custom action filter:

public class ValidateModelFilterAttribute: ActionFilterAttribute
{
    /// 
    public override void OnActionExecuting(ActionExecutingContext context)
    {
        if (!context.ModelState.IsValid)
        {
            var errs = context.ModelState.Keys.Select(
                key => context.ModelState[key].Errors.Select(e =>
                    $"{key}: {(!string.IsNullOrWhiteSpace(e.ErrorMessage) ? e.ErrorMessage : e.Exception.Message)}")
            ).SelectMany(x => x).ToArray();

            context.Result = new ObjectResult(new {Errors: errs})
            {
                StatusCode = (int) HttpStatusCode.BadRequest
            };
        }
    }
}

Decorate controller or method with the custom filter or set it to be used globally.

More info here: https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-2.2

Depending on a scenario simply paste the code below into the Immediate Window

If you happen to use Newtonsoft.Json:

System.IO.File.WriteAllText(@"c:\temp\debug_dump.json", Newtonsoft.Json.JsonConvert.SerializeObject(obj))

No json serializer? Try xml serializer then:

(new System.Xml.Serialization.XmlSerializer(obj.GetType())).Serialize(new System.IO.StreamWriter(@"c:\temp\debug_dump.xml"), obj)

Obviously the above will throw if an object is not serializable

Just wasted way too much time for this:

The Entity Framework provider type 'Npgsql.NpgsqlServices, EntityFramework6.Npgsql' registered in the application config file for the ADO.NET provider with invariant name 'Npgsql' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information.

Obvious perhaps, but not so much anymore while being sure EntityFramework6.Npgsql has been installed... My project used to work a while ago and I could swear I had all the refs intact. After all it would not work otherwise, right...

Anyway, apart from making sure DbProviderFactories and providers are configured, just dbl check EntityFramework6.Npgsql is actually installed / output. If not reinstalling from nuget is a good start. Did work for me ;)

a quick reminder:

Install-Package Costura.Fody
Install-CleanReferencesTarget

More info here and here.

Just a pointer to a very valuable resource ;)