Binding a comma separated list to a List<int> in asp.net web api

Question

The default binder in web api expecst

http://url.com/webapi/Report/?PageIds=3243&PageIds=2365

To bind to

public IHttpActionResult Report(List<int> PageIds){ // exciting webapi code}

I wish to bind http://url.com/webapi/Report/?PageIds=3243,2365

as I am running out of space in my URL to do a GET.

I have created a class public class CommaSeparatedModelBinder :

System.Web.Http.ModelBinding.IModelBinder
    {
        public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
        {
           //Binding in here
        }
     }

and registered this in my WebApiConfig.cs

 var provider = new SimpleModelBinderProvider(
           typeof(List<int>), new CommaSeparatedModelBinder());
            config.Services.Insert(typeof(ModelBinderProvider), 0, provider);

I have altered my method signature to use the model binder like so

 public IHttpActionResult Report( [ModelBinder] List<int> PageIds){ // exciting webapi code}

However a break point in my binder is not being hit (and the list does not get bound).

What else do I need to configure?

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

Make sure to follow all of the steps in this article: Parameter Binding in ASP.NET Web API

It appears you are missing the last step:

With a model-binding provider, you still need to add the [ModelBinder] attribute to the parameter, to tell Web API that it should use a model binder and not a media-type formatter. But now you don’t need to specify the type of model binder in the attribute:
   public HttpResponseMessage Get([ModelBinder] GeoPoint location) { ... }

Also, I've never tried binding to List<int>. You may not be able to model bind to it because it is a build-in type. If so, just box it with a custom class type and make sure to add the [ModelBinder] attribute to the class.

OR....

A better solution: KISS

public IHttpActionResult Report(string PageIds)
{
     var ids = PageIds.Split(',');
     // exciting web api code and/or more robust checking of the split
}

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Sep 1, 2015 at 16:42

natemcmaster

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1 Comment

Loofer Over a year ago

Unfortunately I did not miss that step... just missed putting it in my question :) see the edit! I will try the box and the fallback which I admit had not occurred to me! I prefer to keep things strongly typed if possible!

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