I'm using a grid in an MVVM environment. The grid that starts out with now rows. Once the Add New Row button is clicked the grid adds a row but the user can keep clicking the button and add new rows without any validation on existing rows. How can I either disable the New Row button, perform validation on the current row before adding a new row or client side validate all rows before trying to update to the server. I don't care if a user wants to add several rows and then edit the columns before saving the changes back to the server but I need to validate all required fields first.