How to Add a New Row to DataGrid in MVVM Friendly Way
c#, datagrid, mvvm, wpf
Solution
As far as I understand, you know how to correctly add new items into your data bound collection to result in a new item being added to the `DataGrid` and your question actually relates to how can you do this when the user clicks on the last row in the `DataGrid`. The general way to handle some event in the view model is to create an `Attached Property` (if one does not already exist) that handles that event for you.
For instance, you could create an `Attached Property` that attaches a handler to the relevant event and another of type `ICommand` which you could execute when the event handler is called. Then you could write the functionality of that `ICommand` in your view model (in which you add a new item to your data bound collection) and data bind your `ICommand` implementation to the `Attached ICommand Property`.
As I'm fairly sure you know how to define `Attached Property`s, I won't insult you by showing you. Please let me know if I have misunderstood you, or not made myself clear.
Problem
I have the following `DataGrid` ``` <DataGrid CanUserDeleteRows="True" CanUserAddRows="True" SelectedItem="{Binding SelectedResource, Mode=TwoWay}" ItemsSource="{Binding Path=Resources, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, IsAsync=True}"> ... </<DataGrid> ``` I am using the MVVM pattern to bind to an `ObservableCollection<ResourceViewModel> Resources` and this works great. I have a button that adds a new row and this is done by adding a new `ResourceViewModel` to the `Resources` collection - great. Now, I want the user to be able to click on the empty last row, and this automatically creates a new record in the `DataGrid`. I have made sure the `DataGrid` has `CanUserAddRows=True`. I have made sure the class in the collection `Resources` (`ResourceViewModel`) that I am binding to has a default constructor (no parameters) and I have made sure the collection type is not readonly. When the user clicks on the last row the default constructor fires but to correctly instantiate the new `ResourceViewModel` object in need a reference to either the grid of the `Resources` collection... I suppose I could use and `AttachedCommand` on the `CellBeginEdit` event and then add a new `ResourceViewModel` to the observable collection there, is there a standard way of doing this? Note, I have read the following questions and these are of no help to me - WPF DataGrid - Event for New Rows? - How to add rows with a DataGrid and MVVM Edit. It turns out that I am having problems doing this due to a bug in the WPF `DataGrid`. See Nigel Spencer's Blog. However, his fix is not working for me at the moment...