FromQuery deserializer requires empty constructor

Hi guys 🚀

Describe the bug

As in the title FromQuery requires empty constructor. It is weird because I can use constructors (which initialise all properties) for [FromBody].

System.InvalidOperationException: Could not create an instance of type 'FancyQuery'. Model bound complex types must not be abstract or value types and must have a parameterless constructor. Alternatively, give the 'query' parameter a non-null default value.

To Reproduce

Steps to reproduce the behavior:

1. ASP.NET Core 2.2
2. Controller and DTO/Command

// Controller method

[HttpGet("fancy")]
public async Task<IActionResult> Find([FromQuery] FancyQuery query)
{
   // TODO: add some action
   return Ok();
}

// DTO
public class FancyQuery
  {
    public FancyQuery(int userId, int dumbValue)
    {
      UserId = userId;
      DumbValue = dumbValue;
    }

    public int UserId { get; set; }
    public int DumbValue { get; set; }
  }

Expected behavior

It should works like [FromBody].

Additional context

Add any other context about the problem here. Include the output of dotnet --info

.NET Core SDK (reflecting any global.json):
 Version:   2.2.106
 Commit:    aa79b139a8

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  10.14
 OS Platform: Darwin
 RID:         osx.10.14-x64
 Base Path:   /usr/local/share/dotnet/sdk/2.2.106/

Host (useful for support):
  Version: 2.2.4
  Commit:  f95848e524

.NET Core SDKs installed:
  2.2.106 [/usr/local/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.2.4 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.2.4 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.2.4 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

[ghost]

I can confirm this happens, and it is really frustrating. When you work with DDD, you don’t want people to instantiate your objects with a “default constructor” as this facilitates code corruption. I think the behaviour should be the same as [FromBody]. Is it possible for us to suggest this? Maybe in a future release this can be changed. Thank you.

[pranavkm]

This is by design. FromBody uses serializers such as Newtonsoft.Json which have a different feature set compared to model binding. Model binding - indicated by FromQuery, FromRoute etc, requires that complex types have a parameterless constructor.