A model binder allowing ASP.NET Core binding of primitive arrays as query parameters, modified from: https://stackoverflow.com/q/65544525/264031

CommaSeparatedArrayModelBinder.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Threading.Tasks;

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;
using Microsoft.Extensions.DependencyInjection;

/// <summary>
/// Modified version of code from: https://stackoverflow.com/q/65544525/264031
/// </summary>
namespace AspMvc.Binding
{
	public class CommaSeparatedArrayModelBinderProvider : IModelBinderProvider
	{
		public IModelBinder GetBinder(ModelBinderProviderContext context)
		{
			if(context == null)
				throw new ArgumentNullException(nameof(context));

			return CommaSeparatedArrayModelBinder.IsSupportedModelType(context.Metadata.ModelType)
				? new CommaSeparatedArrayModelBinder() : null;
		}
	}

	public class CommaSeparatedArrayModelBinder : IModelBinder
	{
		private static Task CompletedTask => Task.CompletedTask;

		private static readonly Type[] supportedElementTypes = {
			typeof(int), typeof(long), typeof(short), typeof(byte),
			typeof(uint), typeof(ulong), typeof(ushort), typeof(Guid)
		};

		public Task BindModelAsync(ModelBindingContext bindingContext)
		{
			if(!IsSupportedModelType(bindingContext.ModelType))
				return CompletedTask;

			var providerValue = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);

			if(providerValue == ValueProviderResult.None)
				return CompletedTask;

			// Each value self may contains a series of actual values, split it with comma
			var strs = providerValue.Values.SelectMany(s => s.Split(',', StringSplitOptions.RemoveEmptyEntries)).ToList();

			if(!strs.Any() || strs.Any(s => string.IsNullOrWhiteSpace(s)))
				return CompletedTask;

			var elementType = bindingContext.ModelType.GetElementType();
			if(elementType == null)
				return CompletedTask;

			var realResult = CopyAndConvertArray(strs, elementType);

			bindingContext.Result = ModelBindingResult.Success(realResult);

			return CompletedTask;
		}

		internal static bool IsSupportedModelType(Type modelType)
		{
			return modelType.IsArray && modelType.GetArrayRank() == 1
				&& modelType.HasElementType
				&& supportedElementTypes.Contains(modelType.GetElementType());
		}

		private static Array CopyAndConvertArray(IList<string> sourceArray, Type elementType)
		{
			var targetArray = Array.CreateInstance(elementType, sourceArray.Count);
			if(sourceArray.Count > 0) {
				var converter = TypeDescriptor.GetConverter(elementType);
				for(var i = 0; i < sourceArray.Count; i++)
					targetArray.SetValue(converter.ConvertFromString(sourceArray[i]), i);
			}
			return targetArray;
		}
	}

	public static class CommaSeparatedArrayModelBinderServiceCollectionExtensions
	{
		private static int FirstIndexOfOrDefault<T>(this IEnumerable<T> source, Func<T, bool> predicate)
		{
			var result = 0;

			foreach(var item in source) {
				if(predicate(item))
					return result;

				result++;
			}

			return -1;
		}

		private static int FindModelBinderProviderInsertLocation(this IList<IModelBinderProvider> modelBinderProviders)
		{
			var index = modelBinderProviders.FirstIndexOfOrDefault(i => i is FloatingPointTypeModelBinderProvider);
			return index < 0 ? index : index + 1;
		}

		public static void InsertCommaSeparatedArrayModelBinderProvider(this IList<IModelBinderProvider> modelBinderProviders)
		{
			// Argument Check
			if(modelBinderProviders == null)
				throw new ArgumentNullException(nameof(modelBinderProviders));

			var providerToInsert = new CommaSeparatedArrayModelBinderProvider();

			// Find the location of SimpleTypeModelBinder, the CommaSeparatedArrayModelBinder must be inserted before it.
			var index = modelBinderProviders.FindModelBinderProviderInsertLocation();

			if(index != -1)
				modelBinderProviders.Insert(index, providerToInsert);
			else
				modelBinderProviders.Add(providerToInsert);
		}

		public static MvcOptions AddCommaSeparatedArrayModelBinderProvider(this MvcOptions options)
		{
			if(options == null)
				throw new ArgumentNullException(nameof(options));

			options.ModelBinderProviders.InsertCommaSeparatedArrayModelBinderProvider();
			return options;
		}

		public static IMvcBuilder AddCommaSeparatedArrayModelBinderProvider(this IMvcBuilder builder)
		{
			builder.AddMvcOptions(options => AddCommaSeparatedArrayModelBinderProvider(options));
			return builder;
		}
	}
}