MVC Core: Prefer action which best matches query parameters

RouteWithQueryParamatersAttribute.cs

using Microsoft.AspNetCore.Mvc.ActionConstraints;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using MoreLinq;
using System;
using System.Linq;

namespace Api.Constraints
{
	/// <summary>
	/// Use amount of matching query parameters to find the right action.
	/// </summary>
	[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
	public class RouteWithQueryParamatersAttribute : Attribute, IActionConstraint
	{
		public int Order => 0;

		public bool Accept(ActionConstraintContext context)
		{
			var queryKeys = context.RouteContext.HttpContext.Request.Query.Keys;

			var actionIdsAndCount = context.Candidates.Select(
				candidate =>
				{
					// Get a list of all of the actions parameters which come from the query string.
					var paramaters =
						candidate.Action.Parameters
								 .Where(paramater => paramater.BindingInfo.BindingSource.Id == BindingSource.Query.Id)
								 .ToList();

					return new
					{
						ParamaterCount = paramaters.Count,
						// The number of parameters which can be provided by the current query string.
						MatchingCount =
						paramaters.Count(
							paramater => queryKeys.Contains(paramater.Name)),
						ParamaterId = candidate.Action.Id
					};
				}).ToList();

			/*
			 * If none of the candidates are able to use the query string (perhaps[1] because there isn't a query string),
			 * accept an action which doesn't need any query parameters.
			 *
			 * [1] It would be simplest to say that an action with no query parameters only matches
			 * a request with no query parameters. This isn't robust, though, because a query string could be used eg for authentication.
			 * Therefor, the rule is that an action with no query parameters matches a request with no query parameters *relevant to the actions*,
			 * as defined above.
			 */
			if (actionIdsAndCount.All(action => action.MatchingCount == 0))
				return actionIdsAndCount.First(action => action.ParamaterId == context.CurrentCandidate.Action.Id).ParamaterCount == 0;

			// Get the actions which have the highest percentage of matched query parameters.
			var highest = actionIdsAndCount
							// If an action doesn't accept any query parameters, it only matches a request without any
							// query parameters, and that was already handled earlier.
						  .Where(item => item.ParamaterCount > 0)
							// Get the matches with the greatest percentage of used parameters.
						  .MaxBy(item => item.MatchingCount / item.ParamaterCount)
							// If multiple actions have the same percentage, prefer the action with the highest number
							// of used parameters.
							// A common case would be if one controller accepts 2 parameters, and another accepts the same 2 and another 1, and
							// the request has those 3 parameters - both actions have %100 of their parameters matching, so prefer the one which has
							// 3 paramaters matching.
						  .MaxBy(item => item.MatchingCount);

			// The current action is accepted if it is one of the highest.
			return highest.Any(action => action.ParamaterId == context.CurrentCandidate.Action.Id);
		}
	}
}

how to use it? i mean where to register it?

Just add the class to your code, and add the attribute to the controller. You don't have to register it. That being said, I personally stopped using it. There are enough edge cases etc where it doesn't work, I just just a different endpoint when I need something like that.

…

On Thu, Apr 1, 2021, 12:28 PM Amaan Khan ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ how to use it? i mean where to register it? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://gist.github.com/eb10736533f2e63e54fcbac6a95d752e#gistcomment-3689806>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA7B3KIC476FFMLNIGS4FKLTGSNLNANCNFSM42HM6VIA> .