.NET CORE WEB API accept list of integers as an input param in HTTP GET API

Question

I am using .net core 3+ web api.

Below is how my action looks like below, it uses HTTP GET and I want to pass few fields and one of the fields is a list of integers.

[HttpGet]
[Route("cities")]
public ActionResult<IEnumerable<City>> GetCities([FromQuery] CityQuery query)
{...}

and here is CityQuery class -

public class CityQuery
{
 [FromQuery(Name = "stateids")]
 [Required(ErrorMessage = "stateid is missing")]
 public string StateIdsStr { get; set; }
 public IEnumerable<int> StateList 
 {
 get
 {
 if (!string.IsNullOrEmpty(StateIdsStr))
 {
 var output = StateIdsStr.Split(',').Select(id =>
 {
 int.TryParse(id, out var stateId);
 return stateId;
 }).ToList();
 return output;
 }
 return new List<int>();
 }
 }
}

Is there a generic way I can use to accept list of integers as input and not accept string and then parse it?

Or is there a better way to do this? I tried googling but could not find much. Thanks in advance.

• Panagiotis Kanavos: There's no convention on passing value arrays in query parameters. Each language and frameworks uses its own conventions. Have you tried [FromUri] int[] stateList ? How do you want to pass those parameters?
• Panagiotis Kanavos: ASP.NET Core's convention is to allow multiple parameter instances, eg ids=1&ids=2&ids=3 and bind them to a single ids array

Answer 1

This can help

 [HttpGet]
 [Route("cities")]
 public ActionResult<IEnumerable<City>> GetCities([FromQuery] int[] stateids)
 {
 ...
 }

but the query string will change to https://localhost/api/controller/cities?stateids=1&stateids=2&stateids=3

If you required comma separated query string with integer, you can go for Custom model binder

https://learn.microsoft.com/en-us/aspnet/core/mvc/advanced/custom-model-binding?view=aspnetcore-3.1

Answer 2

You can use custom model binding, below is a working demo:

Model:

public class CityQuery
{
 public List<int> StateList{ get; set; }
}

CustomModelBinder:

public class CustomModelBinder: IModelBinder
{
 public Task BindModelAsync(ModelBindingContext bindingContext)
 {
 if (bindingContext == null)
 {
 throw new ArgumentNullException(nameof(bindingContext));
 }
 var values = bindingContext.ValueProvider.GetValue("stateids");
 if (values.Length == 0)
 {
 return Task.CompletedTask;
 }
 var splitData = values.FirstValue.Split(',');
 var result = new CityQuery()
 {
 StateList = new List<int>()
 };
 foreach(var id in splitData)
 {
 result.StateList.Add(int.Parse(id));
 }
 bindingContext.Result = ModelBindingResult.Success(result);
 return Task.CompletedTask;
 }
}

Applying ModelBinding Attribute on Action method:

[HttpGet]
[Route("cities")]
public ActionResult GetCities([ModelBinder(BinderType = typeof(CustomModelBinder))] CityQuery query)
{
 return View();
}

when the url like /cities?stateids=1,2,3, the stateids will be filled to StateList

• mj1313: Hi @Yasser Shaikh, can this answer help you solve the problem?

Answer 3

I think you just need to use [FromUri] before int array parameter :

public ActionResult<IEnumerable<City>> GetCities([FromUri] int[] stateList)

And request would be like :

/cities?stateList=1&stateList=2&stateList=3 

• Yasser Shaikh: I want to pass stateids=1,2,3
• Panagiotis Kanavos: @YasserShaikh that's one string parameter named stateids with value 1,2,3. There's no convention on passing value arrays in query parameters
• Ömür Efe Güçlü: You can take a look at this post : stackoverflow.com/questions/9584573/…