Connecting to multiple databases in MVC web application

In your web.config file, you could define your two connection strings:

    <add name="DevelopmentDB" providerName="System.Data.SqlClient"
        connectionString="Data Source=sql-dev.example.com;Initial Catalog=MyDB;User Id=MyUser;Password=MyPassword" />
    <add name="ProductionDB" providerName="System.Data.SqlClient"
        connectionString="Data Source=sql-prod.example.com;Initial Catalog=MyDB;User Id=MyUser;Password=MyPassword" />
</connectionStrings>

Then, in your (base) controller, you could create a method that returns the appropriate connection string based upon the request, such as:

internal string ConnectionString
{
    get
    {
        return getConnectionStringByServerName(this.HttpContext.Request.ServerVariables["SERVER_NAME"]);
    }
}

internal string getConnectionStringByServerName(string serverName)
{
    if (serverName.Equals("localhost"))
    {
        return WebConfigurationManager.ConnectionStrings["DevelopmentDB"].ConnectionString;
    }
    else
    {
        return WebConfigurationManager.ConnectionStrings["ProductionDB"].ConnectionString;
    }
}