I am wondering why this situation is not resulting in an ambiguous reference between types, one a class within our library and one an external struct. Consider the following-

External struct-

namespace External.Models
{
    public struct ProxyUser
    {
        public string Username { get; set; }
        public string Password { get; set; }
    }
}

Our class-

namespace MyApp.Configuration
{
    public class ProxyUser
    {
        public string Username { get; set; }
        public string Password { get; set; }
    }
}

Then the calling code approximates-

using External.Models;

namespace MyApp.Configuration.Factories
{
    sealed class Factory
    {
        public async Task<T> BuildConfiguration<T>()
        {
            var proxy = new ProxyUser { Username = username, Password = password }; // I would expect this to be ambiguous, but it references out class
        }
    }
}

This is a NetStandard 2.0 library if that makes a difference. Behavior is the same if I make our class a struct. Why isn't this ambiguous?

EDIT - Class is sealed, again if that makes a difference...

ANSWER

As @Sinatr mentioned, it appears to be related to this question- https://stackoverflow.com/a/25437586/14872099

This is a demonstration of the different behaviors I observed.

This resolves to our MyApp.Configuration.ProxyUser-

using External.Models;

namespace MyApp.Configuration.Factories
{
    sealed class Factory
    {
        public async Task<T> BuildConfiguration<T>()
        {
            var proxy = new ProxyUser { Username = username, Password = password }; // resolves to our class
        }
    }
}

This resolves to the external struct-

namespace MyApp.Configuration.Factories
{
    using External.Models;

    sealed class Factory
    {
        public async Task<T> BuildConfiguration<T>()
        {
            var proxy = new ProxyUser { Username = username, Password = password }; // resolves to external struct
        }
    }
}

Moving our class to another namespace creates ambiguity-

using External.Models;
using MyApp.Configuration.Models; // moved our class to this namespace

namespace MyApp.Configuration.Factories
{
    sealed class Factory
    {
        public async Task<T> BuildConfiguration<T>()
        {
            var proxy = new ProxyUser { Username = username, Password = password }; // this is ambiguous
        }
    }
}