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Azure Function c# - Retrieve list of subscription's WebApp

We want to create an azure function in c# that retrieve the list of azure web app contained in the subscription (basically we want to call dynamically, for each webapp, the same API endpoint changing the subdomain of the api).
It's possible with c# retrieve the list of the web app contained in the same azure function subscriptions?
Usually we connect to the master database, we query the sys.databases to collect the dbname and understand the webapp names. But we are searching for a smartest way.

If you're in C# land, I'd look at using the ArmClient class to retrieve what you're looking for.
Install these (I've got a few others installed but start with that and see how you go, there may be a couple of others needed) Nuget packages ...
Azure.Identity;
Azure.ResourceManager;
Azure.ResourceManager.AppService
... and from there, using the DefaultCredential approach (if you've never used it, read up on it here -> https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/identity/Azure.Identity/README.md) you can query your subscriptions webApps ...
using Azure.Identity;
using Azure.ResourceManager;
using Azure.ResourceManager.AppService;
using System;
using System.Threading.Tasks;
namespace AzureManagement
{
internal class Program
{
static void Main(string[] args)
{
GetAzureResources().Wait();
}
static async Task GetAzureResources()
{
var credential = new DefaultAzureCredential();
var armClient = new ArmClient(credential);
var subscription = await armClient.GetDefaultSubscriptionAsync();
var webSitesEnumerator = subscription.GetWebSitesAsync().GetAsyncEnumerator();
try
{
while (await webSitesEnumerator.MoveNextAsync())
{
var webSite = webSitesEnumerator.Current;
Console.WriteLine($"Web App Name ........ {webSite.Data.Name}");
Console.WriteLine($"Default Host Name ... {webSite.Data.DefaultHostName}\n");
}
}
finally
{
await webSitesEnumerator.DisposeAsync();
}
Console.ReadLine();
}
}
}
The above is obviously not a function app but the core code will still work for you and can be ported as need be.
Note: I could be telling you how to suck eggs, but, once deployed to Azure, you'll need to do the necessary work to ensure that the function app has the required access to retrieve all of the resource information you're looking for.
If you're unfamiliar with that, read up on the managed identity concept. It's very easy to setup -> https://learn.microsoft.com/en-us/azure/app-service/overview-managed-identity

Yes, one easy way is to use HttpClient and send a request to Azure Rest API:
GET https://management.azure.com/subscriptions/{subscriptionId}/providers/Microsoft.Web/sites?api-version=2022-03-01
https://learn.microsoft.com/en-us/rest/api/appservice/web-apps/list
PS: you first need to acquire an authentication token.
https://www.youtube.com/watch?v=6b1J03fDnOg&t=329s

Is it possible to persist an environment setting from within an Azure function?

I've created an Azure Function that retrieves new form inputs from a website, processes them and stores the result in another system by using an API call. I only want to retrieve the form inputs that have not been processed before. This is supported by the website.
I'm reading the timestamp of the most recent form input that has already been processed. This works fine.
I'm using the following function to read the setting from the Azure function environment:
private static string GetEnvironmentVariable(string name)
{
return System.Environment.GetEnvironmentVariable(name, EnvironmentVariableTarget.Process);
}
After I've processed a form input, I store the timestamp of the form with the following function:
private static void SetEnvironmentVariable(string name, string value)
{
System.Environment.SetEnvironmentVariable(name, value, EnvironmentVariableTarget.Process);
}
Everything seems to be working fine. I see in the logs that form inputs don't get processed more than once. However, when I take a look at the environment variables in the Azure dashboard, I can see that the initial value of the variable is still present. This initial value will be used when the environment 'shuts down' and is restarted (e.g. after changing the value of another environment variable).
I've tried to change the target from 'Process' to 'Machine', but this results in access control errors. There are some questions on SO that are related to my issue, but none of them provides me with an answer for my situation.
I would like to know whether:
Environment variables are the / a suited solution for my use case;
If so, how can I prevent that a variable will be reset to its initial value after resetting the Azure environment.
Thanks in advance!

Firstly, the Environment.SetEnvironmentVariable method already worked in your case.
Here is an answer from Hury Shen:
When you set the variable by Environment.SetEnvironmentVariable, it
will not show in application setting. But we can use it by
Environment.GetEnvironmentVariable as expected. Although the solution
you mentioned is not so good, but it can implement your requirement.
The adverse effect is when you restart the function app, the variables
will be lost.
About the target Machine: The environment variable is stored or retrieved from the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment key in the Windows operating system registry. This value should be used on .NET implementations running on Windows systems only.
One way to achieve but not set inside code:
In App Service, you can set app settings outside of your app code.
Then you can access them in any class using the standard ASP.NET Core
dependency injection pattern:
using Microsoft.Extensions.Configuration;
namespace SomeNamespace
{
public class SomeClass
{
private IConfiguration _configuration;
public SomeClass(IConfiguration configuration)
{
_configuration = configuration;
}
public SomeMethod()
{
// retrieve nested App Service app setting
var myHierarchicalConfig = _configuration["My:Hierarchical:Config:Data"];
// retrieve App Service connection string
var myConnString = _configuration.GetConnectionString("MyDbConnection");
}
}
}

managing static data within WCF

I am working within a solution that has a static logging object in a library that is shared among the projects. This is how it is structured:
public class AppLog
{
private static string _logFile;
private static string _appName;
public static string AppName
{
get { return _appName; }
set
{
_appName = value;
InitLogFilePath(); // initializes _logFile according to _appName
}
}
public static Write(string msg)
{
// writes to _logFile
}
}
It works fine for the various Windows apps and Windows services: They can initialize AppLog.AppName upon startup and AppLog.Write can be called throughout the code. Shared modules write to a file named according to the initialization of AppName.
The problem I have is using this within WCF web services. The web services are configured for InstanceContextMode.PerCall. AppLog.AppName is being initialized according to ServiceHostBase.Description.Name. But since multiple web services run within the same AppDomain this static data is shared. So one ws call sets AppLog.AppName and it is changed by the next call, which may have a different ServiceHostBase.Description.Name.
How can this be restructured so that AppLog.Write can still be used throughout the projects in my solution but handle the naming differently for each web service?
If could tell whether the code is running within a web service, and if I could retrieve the ServiceHostBase.Description of the service, then I could maintain a lookup for the appropriate file name. But I have not yet found a way to do this.

Given the way your logging is structured there is not a good solution.
Most logging libraries are structured so that you create an instance of the logger, pass the instance any application specific data (like AppName), and then store that instance in a private static member. The static storage is in the application, not the logging library. This avoids the sharing conflict that you have and still only creates a small fixed number of logger instances.
To illustrate the point, here's a standard log4net example from CodeProject log4net tutorial. This code passes the current class name to the instance of the logger.
private static readonly log4net.ILog log = log4net.LogManager.GetLogger
(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
My suggestion is to look at changing to log4net or any of the other logging packages available on NuGet.

Given your situation, AppName is not where is should be. You need a per-webservice logging facade that hold the AppName and pass the core "Write" logic down to your current AppLog. Then each of the web service has its own LogFacade instance.
class LogFacade
{
public string AppName {get; private set;}
LogFacade(string appName)
{
AppName = appName;
}
public void Write(string msg)
{
AppLog.Write(string.format("[{0}]{1}", AppName, msg));
}
}
Or as ErnieL said, take a look at log4net.

How can I get the URL of the current page from within a C# App_Code class?

I have a logging class that, well, logs things. I would like to add the ability to automatically have the current page be logged with the messages.
Is there a way to get the information I'm looking for?
Thanks,

From your class you can use the HttpContext.Current property (in System.Web.dll). From there, you can create a chain of properties:
Request
Url and RawUrl
The underlying object is a Page object, so if you cast it to that, then use any object you would normally use from within a Page object, such as the Request property.

It's brittle and hard to test but you can use System.Web.HttpContext.Current which will give you a Request property which in turn has the RawUrl property.

public static class MyClass
{
public static string GetURL()
{
HttpRequest request = HttpContext.Current.Request;
string url = request.Url.ToString();
return url;
}
}
I tried to break it down a little :)

In the past I've also rolled my own logging classes and used Console.Writeln() but really there are a number of good logging options that already exist so why go there? I use NLog pretty much everywhere; it is extremely flexible with various log output destinations including console and file, lots of log format options, and is trivial to set up with versions targeting the various .net frameworks including compact. Running the installer will add NLog config file options to the Visual Studio Add New Item dialog. Using in your code is simple:
// declare in your class
private static Logger logger = LogManager.GetCurrentClassLogger();
...
// use in your code
logger.Debug(() => string.Format("Url: {0}", HttpContext.Current.Request.Url));

WebService and Configuration

I created a WebService using the .NET 2.0 framework, a class based on an interface that has the WebServiceAttribute and hosting it using IIS and a ASMX file. The WebService currently loads its configuration from one XML file.
I'd like to create multiple instance of this service where each loads it own configuration.
By coping the ASMX file I can create a clone of the webservice under a different name which will be based on exact the same implementation. But it also loads the exact same configuration file which makes it rather useless.
So my question is: What is the best way to create an arbitrary number of WebServices that are based on one class, living in one IIS virtual directory where each is loading a different configuration file?
Solution
With the help of Pavel Chuchuva's answer I created the following code to handle the loading of the configuration:
public class WebConfigManager
{
public static T Load<T>() where T: new()
{
string location =
HttpContext.Current.Request.PhysicalPath + ".config";
if (HttpContext.Current.Cache[location] is T)
{
return (T)HttpContext.Current.Cache[location];
}
using (Stream s =
new FileStream(location, FileMode.Open, FileAccess.Read))
{
return (T)(HttpContext.Current.Cache[location] =
new XmlSerializer(typeof(T)).Deserialize(s));
}
}
}
// example of the usage of WebConfigManager
public class MyWebService : IMyWebService
{
Config config = WebConfigManager.Load<Config>();
...

Copy and paste .asmx file to create multiple instances of your web service (e.g. Service1.asmx, Service2.asmx and so on).
Load configuration file based on Context.Request.FilePath value:
public string LoadConfig()
{
string configPath = Server.MapPath(this.Context.Request.FilePath + ".xml");
using (XmlReader reader = XmlReader.Create(configPath))
{
// Will read Service1.asmx.xml, Service2.asmx.xml and so on
}
}

I suggest placing the asmx in different folders and placing a web.config in each of those folders with the setting for that specific instance of the web service. This is the easy and fast way
OR
you could use Web Service Enhancements 3.0 and create a WSE router, redirect a calls to a ASMX to that router and let the router forward the call to the right web service instance and pass additional config. This a more complex way of doing it but it enables u to use a single instance of the web service that's picks the right configuration based on the parameters the router passes it.
For more info on WSE3.0 I point you to the MSDN.
Hope this helps!