Can I Add ConnectionStrings to the ConnectionStringCollection at Runtime?

ConfigurationManager.ConnectionStrings.Add(new ConnectionStringSettings(params));

var cfg = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(@"/");
cfg.ConnectionStrings.ConnectionStrings.Add(new ConnectionStringSettings(params));

cfg.Save();

class ConnectionStringProvider
{
    Dictionary<string, System.Configuration.ConnectionStringSettings> _localStrings = new Dictionary<string, System.Configuration.ConnectionStringSettings>();

    public void AddLocalConnectionString(string name, string connstring)
    {
        System.Configuration.ConnectionStringSettings cs = new System.Configuration.ConnectionStringSettings(name, connstring);
        _localStrings.Add(name, cs);
    }

    public void RemoveLocalConnectionString(string name)
    {
        _localStrings.Remove(name);
    }

    public System.Configuration.ConnectionStringSettings this[string name] {
        get
        {
            return _localStrings.ContainsKey(name) ? _localStrings[name] : System.Configuration.ConfigurationManager.ConnectionStrings[name];
        }
    }
}

aspnet_regiis -pe "connectionStrings" -app "/MyCoolWebApplication" -prov "DataProtectionConfigurationProvider"

ConfigurationManager.ConnectionStrings.Add(new ConnectionStringSettings(params));

ConfigurationManager.ConnectionStrings["myconnection"].ConnectionString = "something";

<add name="myconnection" connectionString="SET AT RUNTIME" ... />