Using [FromQuery] with a .NET controller for an optional boolean query string parameter where presence alone should set it

Question

.NET has [FromQuery] to get query parameters on the path.

For instance my/foo?bar=1 maps to:

public class MyController : Controller
{
    [HttpGet]
    public async Task<Whatever> Foo([FromQuery] int bar, ...

The problem is boolean parameters, which can be passed as ?bar=true but are often passed by presence alone. There's no standard enforcing this either way, but it's really common practice.

So this:

public class MyController : Controller
{
    [HttpGet]
    public async Task<Whatever> Foo([FromQuery] bool? bar, ...

Will have bar as true when my/foo?bar=true, but as null when my/foo?bar.

I need:

• Path my/foo?bar sets bar = true in .NET
• Path my/foo sets bar = false or bar = null (either is fine) in .NET
• Ideally handle the other corner cases:
  • my/foo?bar=1 sets true
  • my/foo?bar=0 sets false
  • my/foo?bar=false sets false

I can write my own IModelBinder from scratch to handle this, but it seems like something that should be out of the box... MVC is 20 odd years old, this must be a commonly solved problem by now?

What's the best practice for these in .NET?