List is empty for httppost in Swagger

currently I'm testing a httppost method with swagger. All the other fields are populated for my endpoint except the list.

Document.cs

public class DocumentAddRequest
{
    public string Name { get; set; }
    public IFormFile File { get; set; }
    public List<Detail> Details { get; set; }
}

Detail.cs

public class Detail
{
    public string PropertyName { get; set; }
    public string PropertyValue { get; set; }
}

I am adding two json objects into Details but when inspecting within my controller endpoint, it's empty.

May I ask how do I get a list to be passed using httppost. One thing to note is I am using FromForm since I'm uploading a file.

I've googled and it looks like swagger UI has a bit of an issue https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/1107 Wondering if anyone else has been able to go around this.

Below is a work demo, you can refer it, hope it can help.

1.Custom model binder like below:

public class MetadataValueModelBinder : IModelBinder
    {
        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            if (bindingContext == null)
                throw new ArgumentNullException(nameof(bindingContext));

            var values = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);

            if (values.Length == 0)
                return Task.CompletedTask;
            var options = new JsonSerializerOptions() { PropertyNameCaseInsensitive = true };

            var deserialized = JsonSerializer.Deserialize(values.FirstValue, bindingContext.ModelType, options);

            bindingContext.Result = ModelBindingResult.Success(deserialized);
            return Task.CompletedTask;
        }
    }

2.Add the model binder to the model class:

[ModelBinder(BinderType = typeof(MetadataValueModelBinder))]
    public class Detail
    {
        public string PropertyName { get; set; }
        public string PropertyValue { get; set; }
    }

3.Result:

You might consider this as a suggestion in case you have a ton of Detail data, inputting multiple objects into Swagger might take time.

We can take the Detail as a JSON string and then deserialize it into a list of "Detail" objects.

E.g:

    [HttpPost(Name = "PostFormData1")]
    public IEnumerable<Detail> PostFormData([FromForm] DocumentAddRequest request)
    {
        var serializerOptions = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };

        var listObject = JsonSerializer.Deserialize<List<Detail>>(request.Details, serializerOptions);
        return listObject;
    }

    public class DocumentAddRequest
    {
        public string Name { get; set; }
        public IFormFile File { get; set; }
        public string Details { get; set; }
    }

    public class Detail
    {
        public string PropertyName { get; set; }
        public string PropertyValue { get; set; }
    }

Swagger Input using following JSON String for Detail data:

[{     "PropertyName": "test",     "PropertyValue": "test2" }, {     "PropertyName": "test3",     "PropertyValue": "test4" }]

Swagger Response:

Debug: