How to add Roles to Windows Authentication in ASP.NET Core

this is working code that I use to check is a user is in a role \ group, please use it at your leisure

using System.Collections.Generic;
using System.DirectoryServices.AccountManagement;
using System.Linq;
using System.Security.Principal;

namespace Santander.IsUserInGroupOrRole_cs
{

public class IsUserInRole
{
    public static bool IsInGroup(string groupName)
    {
        var myIdentity = GetUserIdWithDomain();
        var myPrincipal = new WindowsPrincipal(myIdentity);
        return myPrincipal.IsInRole(groupName);
    }

    public bool IsInGroup(List<string> groupNames)
    {
        var myIdentity = GetUserIdWithDomain();
        var myPrincipal = new WindowsPrincipal(myIdentity);

        return groupNames.Any(group => myPrincipal.IsInRole(group));
    }

    public static WindowsIdentity GetUserIdWithDomain()
    {
        var myIdentity = WindowsIdentity.GetCurrent();
        return myIdentity;
    }

    public static string GetUserId()
    {
        var id = GetUserIdWithDomain().Name.Split('\\');
        return id[1];
    }

    public static string GetUserDisplayName()
    {
        var id = GetUserIdWithDomain().Name.Split('\\');

        var dc = new PrincipalContext(ContextType.Domain, id[0]);
        var adUser = UserPrincipal.FindByIdentity(dc, id[1]);
        return adUser.DisplayName;

    }
}
}

With Windows Authentication the roles come from Active Directory, not a database.

You could use Claims Transformation to change the inbound identity on every request to pull extra roles from your database.

public class ClaimsTransformer : IClaimsTransformer
{
    public Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
    {
        ((ClaimsIdentity)principal.Identity).AddClaim(
            new Claim("ExampleClaim", "true"));
        return Task.FromResult(principal);
    }
}

And then wire it up with

app.UseClaimsTransformation(new ClaimsTransformationOptions
{
    Transformer = new ClaimsTransformer()
});

Note that in the current incarnation there's no DI support, so you'll have to manually pull out your database information from DI if that's where it is.