public class FilterModelBinder : IModelBinder
    {
        public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            if (bindingContext == null) throw new ArgumentNullException("bindingContext");
            string filter = controllerContext.HttpContext.Request.Form["filter"];
            if (string.IsNullOrEmpty(filter)) return null;
            PromoCodeNewModel_Filter fi = JsonConvert.DeserializeObject<PromoCodeNewModel_Filter>(filter);
            IFilterable t = JsonConvert.DeserializeObject(filter, bindingContext.ModelType) as IFilterable;
            if (t == null) return null;
            if (t.Pager == null)
            {
                t.Pager = new Pager();
            }
            return t;
        }
        

    }

public class FilterModelBinderProvider : IModelBinderProvider
    {
        public System.Web.Mvc.IModelBinder GetBinder(Type modelType)
        {
            if (typeof(IFilterable).IsAssignableFrom(modelType))
            {
                return new FilterModelBinder();
            }
            return null;
        }
    }

    /// <summary>
    /// An <see cref="IModelBinder"/> which binds models from the request body using an <see cref="IInputFormatter"/>
    /// when a model has the binding source <see cref="BindingSource.Body"/>.
    /// </summary>
    public class FilterModelBinder : IModelBinder
    {
        private readonly IList<IInputFormatter> formatters;
        private readonly IHttpRequestStreamReaderFactory readerFactory;
        public FilterModelBinder(IList<IInputFormatter> formatters, IHttpRequestStreamReaderFactory readerFactory)
        {
            this.formatters = formatters;
            this.readerFactory = readerFactory;
        }
        /// <inheritdoc />
        public async Task BindModelAsync(ModelBindingContext bindingContext)
        {
            await Task.Run(() =>
            {
                if (bindingContext == null) throw new ArgumentNullException("bindingContext");
                string filter = bindingContext.HttpContext.Request.Form["filter"];
                if (string.IsNullOrEmpty(filter)) return;
                IFilterable t = JsonConvert.DeserializeObject(filter, bindingContext.ModelType) as IFilterable;
                if (t == null) return;
                if (t.Pager == null)
                {
                    t.Pager = new Pager();
                }
                bindingContext.Result = ModelBindingResult.Success(t);
            });
        }
    }

    /// <summary>
    /// An <see cref="IModelBinderProvider"/> for deserializing the request body using a formatter.
    /// </summary>
    public class FilterModelBinderProvider : IModelBinderProvider
    {
        private readonly IList<IInputFormatter> formatters;
        private readonly IHttpRequestStreamReaderFactory readerFactory;

        public FilterModelBinderProvider(IList<IInputFormatter> formatters, IHttpRequestStreamReaderFactory readerFactory)
        {
            this.formatters = formatters;
            this.readerFactory = readerFactory;
        }
        /// <inheritdoc />
        public IModelBinder GetBinder(ModelBinderProviderContext context)
        {
            if (typeof(IFilterable).IsAssignableFrom(context.Metadata.ModelType))
                return new FilterModelBinder(formatters, readerFactory);
            return null;
        }
    }