Call custom ModelBinder in .NET Core

Question

I'm creating a custom ModelBinder in .NET Core 1.1.0, and I think I have it mostly figured out. I want to use this binder only when I specifically want to, but I can't figure out how to accomplish this. I want this model binder to be ignored when I don't call it, but when I call it I want all others to be ignored. How can I accomplish this?

The two things that seem feasible are the parameter attributes [Bind] and [ModelBinder] , but neither of these really works.

I first tried the below:

[HttpGet]
public async Task<IActionResult> Get([Bind("test")] int userId)
{
    // stuff
}

When my custom IModelBinderProvider is hit, the ModelBinderProviderContext contains a BindingInfo property, which in turn contains an IPropertyFilterProvider . When debugging, that filter provider contains a collection called Include with my value of test . There doesn't appear to be any way to check for that programmatically, however--there's no way that I can find to actually access that collection. It's null if nothing is set, so I could hypothetically check for null, but that's very messy and isn't a good idea.

To illustrate, here's the debugger info for the ModelBinderProviderContext :

Next, I tried using this code:

[HttpGet]
public async Task<IActionResult> Get(
    [ModelBinder(BinderType = typeof(MyModelBinder))] int userId
)
{
    // stuff
}

This attribute appears to have no effect whatsoever. It does not force MyModelBinder to be used; model binders are used in the order specified in Startup.cs (the list in MvcOptions ).

Answer 1

The PropertyFilterProvider contains a BindAttribute instance which implements the IPropertyFilterProvider interface. You could cast the instance to a BindAttribute and access the Include property:

var bindAttribute = context.BindingInfo.PropertyFilterProvider as BindAttribute;
var include = bindAttribute?.Include;

Keep in mind that the cast may not succeed, resulting in bindingAttribute being null .