public static void DeleteCertificatesForUser(AmazonIdentityManagementServiceClient client, string username)
{
ListSigningCertificatesResponse response =
client.ListSigningCertificatesAsync(new ListSigningCertificatesRequest() { UserName = username }).Result;
foreach (SigningCertificate cert in response.Certificates)
{
client.DeleteSigningCertificateAsync(new DeleteSigningCertificateRequest() { UserName = username, CertificateId = cert.CertificateId }).Wait();
}
}