Problem
The problem I had is that I had a search page, which went to a search results page that could be paginated. The paginator needs to know the search criteria used, so it can create a link on the page which calls for page x with the correct search criteria set.
I originally had code that looked like this in my view:
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<div class="btn-group btn-group-justified"> @Html.PageLinks(Model.PagingInfo, x => Url.Action("Search", new { shortName = Model.SearchCriteria.ShortName, soundsLike = Model.SearchCriteria.SoundsLike, postCode = Model.SearchCriteria.PostCode, policyNumber = Model.SearchCriteria.PolicyNumber, previousVersions = Model.SearchCriteria.PreviousVersions, page = x })) </div> |
The search criteria class has a list of properties that can be searched for. The problem is, I didn’t want to have a list of all the properties in any views that use it, I wanted to be able to say:
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<div class="btn-group btn-group-justified"> @Html.PageLinks(Model.PagingInfo, x => Url.Action("Search", new { searchCriteria = Model.SearchCriteria.ShortName, page = x })) </div> |
However this code does not work, as you can’t pass a complex object into Url.Action. Serialising this into a query string doesn’t work. I looked into how I could do this via fixing the serialisation problem, but chose a different approach in the end which is documented below.
One Solution
Url.Action can take an anonymous object, or it can take a RouteValueDictionary. So the first step was to put a ToRouteValueDictionary in my model. This wasn’t going to work for me, because my domain classes don’t access System.Web (or any data access routines for that matter, I use IOC).
So I decided on an extension method that used reflection to create a Dictionary, this only adds results if the value isn’t null, which means we don’t have lots of null querystring parameters in practice:
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using System; using System.Collections.Generic; using System.ComponentModel; namespace Ncs.Ida.Common.ExtensionMethods { public static class ToDictionaryExtensionMethod { public static IDictionary<string, object> ToDictionary(this object source) { return source.ToDictionary<object>(); } public static IDictionary<string, T> ToDictionary<T>(this object source) { if (source == null) throw new ArgumentNullException(nameof(source)); var dictionary = new Dictionary<string, T>(); foreach (PropertyDescriptor property in TypeDescriptor.GetProperties(source)) { AddPropertyToDictionary(property, source, dictionary); } return dictionary; } private static void AddPropertyToDictionary<T>(PropertyDescriptor property, object source, Dictionary<string, T> dictionary) { object value = property.GetValue(source); if (value is DateTime) { value = string.Format("{0:dd/MM/yyyy}", value); dictionary.Add(property.Name, (T) value); } else if (value is T) dictionary.Add(property.Name, (T)value); } } } |
The view then is responsible for turning the Dictionary into a RouteValueDictionary
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<div class="btn-group btn-group-justified"> @Html.PageLinks(Model.PagingInfo, x => { var dict = Model.SearchCriteria.ToDictionary(); var routeValueDictionary = new RouteValueDictionary(dict) { { "page", x } }; return Url.Action("Search", routeValueDictionary); }) </div> |
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