如何调用UpdateSource（）来显示DataGrid上的显式绑定？

I have a DataGrid that contains information from a settings object. Currently there is two-way binding between the DataGrid and settings object. However, I want to put a "Save" button in that only binds changes made in the DataGrid to the object if the user clicks the Save button. However, I'm not sure how to call UpdateSource() for my particular case with my DataGrid.I have a DataGrid that contains information fro