How to change ConnectionString easily

Introduction

Everyone who starts a real project in the field of DataBase faces to the ConnectionString changing trouble. For small projects that it is not needed to alter the database location, changing the ConnectionString is not a problem, but in bigger projects specially in the time of application packaging, ConnectionString is a headache.

I have searched for a simple way for changing the ConnectionString in RUN TIME. There are many tips and tricks in Internet, but every way has a side effect.

In this article I will show you how you can change the ConnectionString in Run Time like an ordinary attribute.

Using the code

In .Net programming usually we do not alter the Settings class. This class holds the read only attributes of connection strings. By a magic we can change the connection string in Settings class.

Firstly, we create a User Scoped string Attribute in Settings class: 

[global::System.Configuration.UserScopedSettingAttribute()]
public string ConnectionString
{
    get { return (string)this["ConnectionString"]; }
    set { this["ConnectionString"] = value; }
}

This attribute holds the connection string in run time. There are some events that can be utilized for changing the main connection string, PropertyChanged and SettingsLoaded. PropertyChanged fires every time the value of any attribute in the class is changed, and SettingsLoaded fires when the loading process of the program settings is finished. We make two event handlers in the constructor of Settings class. Please note that there is no constructor and the constructor should be coded too.

public Settings()
{
    this.PropertyChanged += 
      new System.ComponentModel.PropertyChangedEventHandler(this.Settings_PropertyChanged);
    this.SettingsLoaded += 
      new System.Configuration.SettingsLoadedEventHandler(this.Settings_SettingsLoaded);
}

Also, we create two handlers:

private void Settings_PropertyChanged(System.Object sender,
         System.ComponentModel.PropertyChangedEventArgs e)
{
    if (e.PropertyName == "ConnectionString")
    {
        this["Original_ConnectionString"] = this.ConnectionString;
    }
}

private void Settings_SettingsLoaded(System.Object sender,
        System.Configuration.SettingsLoadedEventArgs e)
{
    // Advanced codes for post loading process...
}

The Original_ConnectionString is the main connection string of your program that you want to change it. Now every where in your code you can assign a new connection string to ConnectionString and it will be your new connection string. Also, you can define a function to do the job. A good place for defining the function is in Program class. You can use a function like this:

public static void ChangeConnectionString(string connectionstring)
{
    global::[project_namespace].Properties.Settings.Default.ConnectionString = 
        connectionstring;
}

By calling the function and passing the connection string to it, you can change the connection string easily. That's it!!!

Points of Interest

You can do more and you can have more flexible code if you use SettingsLoaded. I leave you with them alone!