When a row is removed, all data in that row is lost. You can also call the Delete method of the DataRow class to just mark a row for removal. Calling RemoveAt is the same as calling Delete and then calling AcceptChanges.
You can use the Clear method to remove all members of the collection at one time.
Dim table As DataTable = CType(DataGrid1.DataSource, DataTable)
Dim rowCollection As DataRowCollection = table.Rows
If rowCollection.Count = 0 ThenExitSubEndIf
rowCollection.RemoveAt(rowCollection.Count - 1)