How to update listview after add new item?

but i bind listview by sqldatasource in aspx page

now if i bind again in cs page then error comes
Both DataSource and DataSourceID are defined on 'list_testimonials'.  Remove one definition.

whats your mean for redatabind

i bind my listview by sqldatasource in aspx page
if i bind in cs then same problem not list view refrese

give me code for this problem to add new item then show in list view

ListView1.DataSource =  "YourDataSource";
ListView1.DataBind();

no i m bind the list view by datasource
how to rebind the listview