Optional [FromBody] Model Binding

[douglasg14b]

Is your feature request related to a problem? Please describe.

I am trying to use optional [FromBody] model binding on a per-endpoint basis.
Example:

        [HttpPost]
        public IActionResult Post([FromBody]SomeClass request = null)
        {
            return Ok();
        }

An empty request body results in the following being returned:

{
  "": [
    "A non-empty request body is required."
  ]
}

Describe the solution you'd like

For properties that have default value ie [FromBody] bool expandRelations = true to not be required in the body of the request.

Additional context

Similar issue here: aspnet/Mvc#6920

[pranavkm]

Setting MvcOptions.AllowEmptyInputInBodyModelBinding should continue to work for this scenario. Are you seeing otherwise?

[douglasg14b]

@pranavkm On a per-endpoint basis similar to the example, not globally for the entire web application.

[pranavkm]

@douglasg14b there isn't a feature to enable this on a per endpoint basis. One option might be to remove \ ignore specific that model validation error in your action.

[douglasg14b]

I suppose this is a feature request then!

I can work around this for now, but it's a bit awkward.

[CrossBound]

I would also like to see a per-request option as mentioned by @hmvs here aspnet/Mvc#6920 (comment)

[mkArtakMSFT]

Thanks for contacting us, @douglasg14b.
We don't think we will get time to implement this feature.
However, this can be done by setting the MvcOptions.AllowEmptyInputInBodyModelBinding to true and implementing a custom ActionFilter which would validate the scenarios you care about explicitly.