Required query string parameter in ASP.NET Core

Question

Using ASP.NET Core 1.1 with VS2015 (sdk 1.0.0-preview2-003131), I have the following controller:

public class QueryParameters
{
    public int A { get; set;          


        

Answer 1

Use model validation. You can define a ViewModel and use DataAnnotations to mark property A as [Required]. Then in your action just check if ModelState.IsValid. You can also easily do this using an action filter as shown in this article: https://msdn.microsoft.com/en-us/magazine/mt767699.aspx