get pfx from Azure KeyVault

test.cs

var secretClient = new SecretClient(new Uri("https://___.vault.azure.net"), new DefaultAzureCredential());
var certClient = new CertificateClient(new Uri("https://___.vault.azure.net"), new DefaultAzureCredential());
var cert = await certClient.GetCertificateAsync("localhostcert");
var secret = await secretClient.GetSecretAsync(cert.Value.Name);

var pfxb = Convert.FromBase64String(secret.Value.Value);
var x509cert = X509CertificateLoader.LoadPkcs12(pfxb, "", X509KeyStorageFlags.MachineKeySet);