public class SomeController : Controller
    {
        private readonly SomeCommand1 _someCommand1;
        private readonly SomeCommand2 _someCommand2;
        .....

        public SomeController (SomeCommand1 someCommand1, SomeCommand2 someCommand2)
        {
            _someCommand1 = someCommand1;
            _someCommand2 = someCommand2;
            .....
        }

        public JsonResult SomeAction1(SomeModel1 model)
        {
            _someCommand1.Execute(model);
            return String.empty;
        }

        public JsonResult SomeAction2(SomeModel2 model)
        {
            _someCommand2.Execute(model);
            return String.empty;
        }
        ...
    }

public class SomeController : Controller
    {
        private readonly SomeCommandLocator _someCommandLocator;

        public SomeController (SomeCommandLocator someCommandLocator)
        {
            _someCommandLocator= someCommandLocator;
        }

        public JsonResult SomeAction1(SomeModel1 model)
        {
            var command = _someCommandLocator.get(model);
            command.Execute()
            return String.empty;
        }

        public JsonResult SomeAction2(SomeModel2 model)
        {
           var command = _someCommandLocator.get(model);
            command.Execute()
            return String.empty;
        }
        ...
    }

public JsonResult ProcessJson(ICommandHandler handler)
        {
            try
            {
                var res = handler.Execute();
                return JsonOk(res);
            }
            catch (BlException e)
            {  
               Response.StatusCode = 400;
               return JsonError();//тут Modelstate просто преобразует в массив строк 
            }
        }