Using topic client, call RegisterMessageHandler which is used to receive messages continuously from the entity. It registers a message handler and begins a new thread to receive messages. This handler is waited on every time a new message is received by the receiver.
subscriptionClient.RegisterMessageHandler(ReceiveMessagesAsync, messageHandlerOptions); References:
https://www.c-sharpcorner.com/article/azure-service-bus-topic-and-subscription-pub-sub/

Explanation:

Box 1: user_impersonation
Box 2: delegated
Example:
1. Select the API permissions section
2. Click the Add a permission button and then:
Ensure that the My APIs tab is selected
3. In the list of APIs, select the API TodoListService-aspnetcore.
4. In the Delegated permissions section, ensure that the right permissions are checked: user_impersonation.
5. Select the Add permissions button.
Box 3: delegated
Example
1. Select the API permissions section
2. Click the Add a permission button and then,
Ensure that the Microsoft APIs tab is selected
3. In the Commonly used Microsoft APIs section, click on Microsoft Graph
4. In the Delegated permissions section, ensure that the right permissions are checked: User.Read. Use the search box if necessary.
5. Select the Add permissions button
Reference:
https://docs.microsoft.com/en-us/samples/azure-samples/active-directory-dotnet-webapp-webapi- openidconnect-aspnetcore/calling-a-web-api-in-an-aspnet-core-web-application-using-azure-ad/

Explanation:

Box 1: Valid root certificate
Scenario: All websites and services must use SSL from a valid root certificate authority.
Box 2: Azure Application Gateway
Scenario:
* Any web service accessible over the Internet must be protected from cross site scripting attacks.
* All Internal services must only be accessible from Internal Virtual Networks (VNets)
* All parts of the system must support inbound and outbound traffic restrictions.
Azure Web Application Firewall (WAF) on Azure Application Gateway provides centralized protection of your web applications from common exploits and vulnerabilities. Web applications are increasingly targeted by malicious attacks that exploit commonly known vulnerabilities. SQL injection and cross-site scripting are among the most common attacks.
Application Gateway supports autoscaling, SSL offloading, and end-to-end SSL, a web application firewall (WAF), cookie-based session affinity, URL path-based routing, multisite hosting, redirection, rewrite HTTP headers and other features.
Note: Both Nginx and Azure Application Gateway act as a reverse proxy with Layer 7 loadbalancing features plus a WAF to ensure strong protection against common web vulnerabilities and exploits.
You can modify Nginx web server configuration/SSL for X-XSS protection. This helps to prevent cross-site scripting exploits by forcing the injection of HTTP headers with X-XSS protection.
Reference:
https://docs.microsoft.com/en-us/azure/web-application-firewall/ag/ag-overview
https://www.upguard.com/articles/10-tips-for-securing-your-nginx-deployment

Explanation: