ClaimsExtensions.cs

public static class ClaimsExtensions
{
    public static string GetClaimValue(this HttpContext context, string type)
    {
        if (context.User.Claims.FirstOrDefault(c => c.Type == type) is Claim claim)
        {
            return claim.Value;
        }
        else throw new ArgumentException(type + " is not found in claims.");
    }
}