Has MediatR been used incorrectly in this project.

[mike-azility]

I have been given a project with no contact possible with the previous developer. I have not used MediatR or the mediator pattern before but I have the feeling it has been done incorrectly in this project.
I have calls like this in the Controllers.
var supplier = _mediator.Send(new GetSupplierDetails.Query(Convert.ToInt32(id), entityId)).Result;
Where GetSupplierDetails class has public class QueryHandler : DataHandler<Query, SupplierModel> and Task Handle that runs some SQL queries.
This means GetSupplierDetails is hardcoded into the calling Controllers. From my limited understanding of MediatR the whole idea is for that not to be the case?
Instead the calls should look more like
var supplier = _mediator.Send(new SupplierModel(Convert.ToInt32(id), entityId)).Result; where SupplierModel is just a class that holds the data? (syntax may not be correct).
Are they wrong or am I missing something?

[jbogard]

Oh that is kinda weird, I've not had the query DTO be an inner class of the handler itself. Sometimes folks make the handler and DTOs be inner classes of the same empty parent class, but a namespace will do the same trick. I do place these classes adjacent to each other on disk though, since queries and handlers are naturally cohesive (they change with each other).

The bigger error here is not using await. The Send method is async and should be awaited. Calling Result can result in deadlocks.