Returning items from dataContext that have the matched ID

I'm trying to implement this method:

public async Task<IEnumerable<Product>> GetListOfProductsAsync(List<int> ids)
{
    var products = await this.GetAllProductsAsync();
    return products.Where(pr => ids.Contains(pr.Id));
}

I want to return a list of products where the ids match.

So for example, if I pass in [1,3,5], the method should return the products with ids 1, 3 and 5. However its not working properly.

When I execute it with only 1 id, it works fine, however when I pass in multiple ids, it fails with this error in Swagger:

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "traceId": "00-f6d957f9875ec28236d9c5abe26500d3-00b20e33f715d7c0-00",
  "errors": {
    "ids": [
      "The value '4,2' is not valid."
    ]
  }
}