App Service: Not able to read connection string setting from App settings

Question

What I am trying to achieve

Hello, I have dotnetcore web Api which is running in Azure App Service server farm. I am trying to read the connection string from app service configuration app settings.

What I have tried so far

• Runtime version: netcoreapp3.1 version-2.31.0.1
• Hosting environment: Azure App Service

Below is how I am trying to read the connection string settings

var configValue = (ConfigurationManager.AppSettings["PNLDBConnectionString"] ?? String.Empty).ToString();

I have added the connection string in app service configuration section as below

As well have added a app settings key as below

But in either way, if I am removing the connection string key from app.config and deploying; then while trying to run any API endpoint throws below error which essentially means the it's not able to read the said connection string property

Any idea, what I could be missing here? Please suggest.

EDIT:

app.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>

    <add key ="Encrypted" value="true"/>
    <add key ="PNLDBConnectionString" value="connection string value"/>

  </appSettings>
</configuration>

Answer 1

• After Adding New ConnectionString in Azure Portal => Configuration => Application settings Add Connection string in appsettings.json file

   "ConnectionStrings": {
      "DefaultConnection": "Server=SQLAzure; Database=PNLDB; Trusted_Connection=True; MultipleActiveResultSets=true"
    }
  

In Startup.cs, Setup configuration settings to overwrite the environmental variables with appsettings.json.

public IConfiguration Configuration { get; set; }
public Startup()
{
    Configuration = new Configuration()
        .AddJsonFile("appsettings.json")
        .AddEnvironmentVariables();    
}

Configure the DB in Startup

public void ConfigureServices(IServiceCollection services)
{
    services
        .AddEntityFramework()
        .AddSqlServer()
        .AddDbContext<ProjectContext>(options =>
        {
            var connString = Configuration.Get("PNLDBConnectionString");
            options.UseSqlServer(connString);
        });
}

• Check the Connection string in KUDU (Control Manager)

Update

var connection = 
    System.Configuration.ConfigurationManager.
    ConnectionStrings["PNLDBConnectionString”].ConnectionString;

Your assembly also needs a reference to System.Configuration.

• I have found that you added value in connection string section and using app settings in code.
• You need to add value in App settings in portal