Configuration::Collection Property

public void CodeExample(DTE2 dte, AddIn addin)
{   // Make sure you have a solution loaded into Visual Studio
    // before running the following example.
    try
    {
        Project prj;
        Configuration config; 
        ConfigurationManager configmgr;
        if (dte.Solution.Projects.Count > 0)
        {
            prj = dte.Solution.Projects.Item(1);
            config = prj.ConfigurationManager.ActiveConfiguration;
            // Returning the Configuration type constant.
            MessageBox.Show(config.Type.ToString());
            // Returns the ConfigurationManager containing the active configuration.
            configmgr = config.Collection;
            // Returns the application containing this active configuration.
            MessageBox.Show(config.DTE.Name);
        }
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}