Umbraco-CMS/src/Umbraco.Web.Common/ModelBinders/HttpQueryStringModelBinder.cs

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.Extensions.Primitives;
using Umbraco.Extensions;

namespace Umbraco.Cms.Web.Common.ModelBinders
{
    /// <summary>
    /// Allows an Action to execute with an arbitrary number of QueryStrings
    /// </summary>
    /// <remarks>
    /// Just like you can POST an arbitrary number of parameters to an Action, you can't GET an arbitrary number
    /// but this will allow you to do it.
    /// </remarks>
    public sealed class HttpQueryStringModelBinder : IModelBinder
    {
        public Task BindModelAsync(ModelBindingContext bindingContext)
        {
            var queryStrings = GetQueryAsDictionary(bindingContext.ActionContext.HttpContext.Request.Query);
            var queryStringKeys = queryStrings.Select(kvp => kvp.Key).ToArray();
            if (queryStringKeys.InvariantContains("culture") == false)
            {
                queryStrings.Add("culture", new StringValues(bindingContext.ActionContext.HttpContext.Request.ClientCulture()));
            }

            var formData = new FormCollection(queryStrings);
            bindingContext.Result = ModelBindingResult.Success(formData);
            return Task.CompletedTask;
        }

        private Dictionary<string, StringValues> GetQueryAsDictionary(IQueryCollection query)
        {
            var result = new Dictionary<string, StringValues>();
            if (query == null)
            {
                return result;
            }

            foreach (var item in query)
            {
                result.Add(item.Key, item.Value);
            }

            return result;
        }
    }
}