public CIMProjectServerConnection ServerConnection {get; set;}

{
    //This workflow would work for 
    var agsFilePath = @"C:\Data\ServerConnectionFiles\AcmeSampleService.ags";

    //ServerConnectionProjectItem supports .ags, .wms, .wmts, .wfs, and .wcs files
    var server_conn_item = ItemFactory.Instance.Create(agsFilePath)
      as ArcGIS.Desktop.Catalog.ServerConnectionProjectItem;

    //Get the server connection - passwords are never returned
    var serverConnection = server_conn_item.ServerConnection as CIMProjectServerConnection;

    //Add to an AGS service connection
    var service_connection = new CIMAGSServiceConnection()
    {
        URL = "URL to the AGS _service_ on the AGS _server_",
        ServerConnection = serverConnection
    };

    // Add a new layer to the map
    var layerParams = new LayerCreationParams(service_connection);
    layerParams.MapMemberPosition = MapMemberPosition.AddToBottom;
    //Note: Needs QueuedTask to run
    var layerCreated = LayerFactory.Instance.CreateLayer<FeatureLayer>(layerParams, map);
}