Winforms-Configuration Manager fails to replace the App.Config's AttachDbFilename |DataDirectory| with the application startup folder

Question

App.Config

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

    <connectionStrings>
        <add name="myConnectionName"
            connectionString="Data Source=(LocalDB)\MSSQLLocalDB;
                AttachDbFilename=|DataDirectory|\AppData\MyDatabase.mdf;
                Initial Catalog=MyDatabase;
                Integrated Security=True; 
                Connection Timeout=360; 
                MultipleActiveResultSets=True;"
            providerName="System.Data.SqlClient"/>
        
    </connectionStrings>

</configuration>

In another file I use

public static class ConnectionStringsHelper
{
    public static string? GetConnectionStringByName(string name)
    {
        // Assume failure.
        string? returnValue = null;

        // Look for the name in the connectionStrings section.
        ConnectionStringSettings settings = ConfigurationManager.ConnectionStrings[name];

        // If found, return the connection string.
        if (settings != null)
            returnValue = settings.ConnectionString;

        return returnValue;
    }

}

I would excpect the Configuration Manager to return the connection string having the |DataDirectory| part replaced by the Application StartupPath. But it Does NOT!! So I had to do it myself replacing the last

return returnValue;

with

returnValue.Replace("|DataDirectory|", Application.StartupPath);

Is this the right way to do it or I am missing something?! Thanx in advance for your help

I have also tried this:

internal static class Program
{
     [STAThread]
     static void Main()
     {
                // To customize application configuration such as set high DPI settings or default font,
                // see https://aka.ms/applicationconfiguration.
                ApplicationConfiguration.Initialize();
    
    
                AppDomain.CurrentDomain.SetData("DataDirectory", Path.GetDirectoryName(Application.ExecutablePath));
    
    
     Application.Run(new Forms.MainForm());
   }
}

But NO luck!! When I substitute the |DataDirectory| with the absolute Path then it works like a charm even without the

AppDomain.CurrentDomain.SetData("DataDirectory", Path.GetDirectoryName(Application.ExecutablePath));

!! Weird!!