We are sorry about the inconvenience caused.
We have analyzed your query and you are using List. List is not implemented from INotifyCollectionChanged interface. So add, remove operations in the itemsource is not reflected in Grid. We have used ObservableCollection instead of List to make this work. Please find the modified sample from below location,
Please let us know if you require further assistance
We are regret to inform you that, we are not able to understand your requirement clearly. Please share simple sample that reproducing the reported issue otherwise share more details regarding your requirement, that would be more helpful for us to serve you better.
I found a solution to quickly add new rows to a tablehttps://peteohanlon.wordpress.com/2008/10/22/bulk-loading-in-observablecollection/