Is there a way to build custom error message for default model binding errors, want to get rid of line and position in the message

Question

{
    "errors": {
        "price": [
            "Could not convert string to decimal: dasdfasdf. Path 'price', line 3, position 22."
        ],
        "userId": [
            "Could not convert string to integer: hsad. Path 'userId', line 6, position 27."
        ]
    },
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|bcaa98d957e1c04181000489a0bc4950.9753735a_"
}

I tried custom model binder, but I need this for specific properties in a model. I also tried the JsonConvert with the property but couldn't find a way to inject the error message in the model state

Answer 1

You can customize the ApiController's ModelState validator response by configuring InvalidModelStateResponseFactory of ApiBehaviorOptions like this:

services.Configure<ApiBehaviorOptions>(options =>
{
    options.InvalidModelStateResponseFactory = actionContext => 
    {
        var errors = actionContext.ModelState
            .Where(e => e.Value.Errors.Count > 0)
            .Select(e => new Error
            {
            Name = e.Key,
            Message = e.Value.Errors.First().ErrorMessage
            }).ToArray();

        return new BadRequestObjectResult(errors);
    }
});

Also, you can read more about ApiController behaviors here .