my ASP.NET application reads an xml file to determine which environment it's currently in (e.g. local, development, production).

It checks this file every single time it opens a connection to the database, in order to know which connection string to grab from the Application Settings.

I'm entering a phase of development where efficiency is becoming a concern. I don't think it's a good idea to have to read a file on a physical disk ever single time I wish to access the database (very often).

I was considering storing the connection string in Application["ConnectionString"]. So the code would be

public static string GetConnectionString
        {
            if (Application["ConnectionString"] == null)
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(HttpContext.Current.Request.PhysicalApplicationPath + "bin/ServerEnvironment.xml");
                XmlElement xe = (XmlElement) xnl[0];

                switch (xe.InnerText.ToString().ToLower())
                {
                    case "local":
                        connString = Settings.Default.ConnectionStringLocal;
                        break;

                    case "development":
                        connString = Settings.Default.ConnectionStringDevelopment;
                        break;

                    case "production":
                        connString = Settings.Default.ConnectionStringProduction;
                        break;

                    default:
                        throw new Exception("no connection string defined");
                }
                Application["ConnectionString"] = connString; 
            }
            return Application["ConnectionString"].ToString();
        }

I didn't design the application so I figure there must have been a reason for reading the xml file every time (to change settings while the application runs?) I have very little concept of the inner workings here. What are the pros and cons? Do you think I'd see a small performance gain by implementing the function above?

THANKS