Passing arguments to Web API model binder

Question

I am trying to create Web API model binder that will bind URL parameters sent by a grid component of a javascript framework. Grid sends URL parameters indicating standard page, pageSize, and JSON formatted sorters, filters, and groupers. The URL string looks like this:

http://localhost/api/inventory?page=1&start=0&limit=10sort=[{"property":"partName","direction":"desc"},{"property":"partStatus","direction":"asc"}]&group=[{"property":"count","direction":"asc"}]

The model in question is Inventory which has simple, Count (int) property and a reference, Part (Part) peoperty (which in turn has Name, Status). The view model/dto is flattened (InventoryViewModel .Count, .PartName, .PartStatus, etc, etc.) I use Dynamic Expression Api then to query domain model, map the result to view model and send it back as JSON. During model binding I need to build the expressions by examining model and view model that are being used.

In order to keep model binder reusable, how can I pass/specify model and view model types being used? I need this in order to build valid sort,filter,and grouping expsessions Note: I don't want to pass these as part of the grid url params!

One idea I had was to make StoreRequest generic (e.g. StoreRequest) but I am not sure if or how model binder would work.

Sample API Controller

// 1. model binder is used to transform URL params into StoreRequest. Is there a way to "pass" types of model & view model to it?
    public HttpResponseMessage Get(StoreRequest storeRequest)
    {
            int total;
            // 2. domain entites are then queried using StoreRequest properties and Dynamic Expression API (e.g. "Order By Part.Name DESC, Part.Status ASC")
            var inventoryItems = _inventoryService.GetAll(storeRequest.Page, out total, storeRequest.PageSize, storeRequest.SortExpression); 
            // 3. model is then mapped to view model/dto
            var inventoryDto = _mapper.MapToDto(inventoryItems);
            // 4. response is created and view model is wrapped into grid friendly JSON
            var response = Request.CreateResponse(HttpStatusCode.OK, inventoryDto.ToGridResult(total));
            response.Content.Headers.Expires = DateTimeOffset.UtcNow.AddMinutes(5);
            return response;
    }

StoreRequestModelBinder

public class StoreRequestModelBinder : IModelBinder
{
    private static readonly ILog Logger = LogManager.GetCurrentClassLogger();

    public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
    {
        Logger.Debug(m => m("Testing model binder for type: {0}", bindingContext.ModelType));
        if (bindingContext.ModelType != typeof(StoreRequest))
        {
            return false;
        }
        var storeRequest = new StoreRequest();
        // ----------------------------------------------------------------
        int page;
        if (TryGetValue(bindingContext, StoreRequest.PageParameter, out page))
        {
            storeRequest.Page = page;
        }
        // ----------------------------------------------------------------
        int pageSize;
        if (TryGetValue(bindingContext, StoreRequest.PageSizeParameter, out pageSize))
        {
            storeRequest.PageSize = pageSize;
        }
        // ----------------------------------------------------------------
        string sort;
        if (TryGetValue(bindingContext, StoreRequest.SortParameter, out sort))
        {
            try
            {
                storeRequest.Sorters = JsonConvert.DeserializeObject<List<Sorter>>(sort);
                // TODO: build sort expression using model and viewModel types
            } 
            catch(Exception e)
            {
               Logger.Warn(m=>m("Unable to parse sort parameter: \"{0}\"", sort), e);
            }
        }
        // ----------------------------------------------------------------
        bindingContext.Model = storeRequest;
        return true;
    }

    private bool TryGetValue<T>(ModelBindingContext bindingContext, string key, out T result)
    {
        var valueProviderResult = bindingContext.ValueProvider.GetValue(key);
        if (valueProviderResult == null)
        {
            result = default(T);
            return false;
        }
        result = (T)valueProviderResult.ConvertTo(typeof(T));
        return true;
    }
}

SSL46 SSL46 · Accepted Answer · 2016-07-22T12:09:16

just change your controller signature like

public HttpResponseMessage Get([ModelBinder(typeof(StoreRequestModelBinder)]StoreRequest storeRequest)

Regards

Passing arguments to Web API model binder

1 Answers