Enrich Token Claims with ASP.NET Core

1services.AddScoped<IClaimsTransformation, AddCustomClaimsToIdentityTransformation>();

 1public class AddCustomClaimsToIdentityTransformation : IClaimsTransformation
 2{
 3    public async Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
 4    {
 5        ClaimsPrincipal clone = principal.Clone();
 6        ClaimsIdentity newIdentity = (ClaimsIdentity)clone.Identity;
 7
 8        // support aad / ad / others, too
 9        Claim? nameId = principal.Claims
10            .FirstOrDefault(c => c.Type == ClaimTypes.NameIdentifier || c.Type == ClaimTypes.Name);
11        if (nameId is null) return principal;
12
13        // request data from your claim source
14        var myClaimData = await _myRepository.GetAdditionClaimsOfUser(nameId).ConfigureAwait(false);
15        foreach (var customClaim in myClaimData)
16        {  
17            newIdentity.AddClaim(new(customClaim.Type, customClaim.Value));
18        }
19
20        return clone;
21    }
22}