The X.509 certificate CN=servicebus.chinacloudapi.cn, OU=Azure, O=Shanghai Blue Cloud Technology Co Ltd, L=Shanghai, S=Shanghai, C=CN is not in the trusted people store.  

The X.509 certificate CN=servicebus.chinacloudapi.cn, OU=Azure, O=Shanghai Blue Cloud Technology Co Ltd, L=Shanghai, S=Shanghai, C=CN chain building failed. 

The certificate that was used has a trust chain that cannot be verified. 

Replace the certificate or change the certificateValidationMode. 

A certificate chain could not be built to a trusted root authority.

string connectionString = "servicebus connection string";

ServiceBusEnvironment.SystemConnectivity.Mode = ConnectivityMode.Https var namespaceManager = NamespaceManager.CreateFromConnectionString(connectionString); if (!namespaceManager.TopicExists("TestTopic"))
{
    namespaceManager.CreateTopic("TestTopic");
}

TopicClient client = TopicClient.CreateFromConnectionString(connectionString, "TestTopic");

BrokeredMessage testMessage = new BrokeredMessage("test message");
testMessage.MessageId = "message id";

client.Send(testMessage);

using Azure.Messaging.ServiceBus;

// the client that owns the connection and can be used to create senders and receivers
ServiceBusClient client;
// The Service Bus client types are safe to cache and use as a singleton for the lifetime
// of the application, which is best practice when messages are being published or read
// regularly.
//
// set the transport type to AmqpWebSockets so that the ServiceBusClient uses the port 443. 
// If you use the default AmqpTcp, you will need to make sure that the ports 5671 and 5672 are open

// TODO: Replace the <NAMESPACE-CONNECTION-STRING> and <QUEUE-NAME> placeholders
var clientOptions = new ServiceBusClientOptions()
{ 
    TransportType = ServiceBusTransportType.AmqpWebSockets
};
client = new ServiceBusClient("<NAMESPACE-CONNECTION-STRING>", clientOptions);