Two-way Data Binding with WPF DataGrids

We’re making use of the the WPF Toolkit’s DataGrid control in my current project and have solved a few things along the way that weren’t entirely obvious to us at the start. One of these things was figuring out how to automatically reflect domain object changes in the UI.

Of the three developers on this project, Nik Clarkson has the most background with WPF and we usually throw out ideas to him and he “translates” what we want to do to into WPF terms and we’re off and running. In the case of getting our UI to reflect domain model changes, he mentioned BindingMode.

I was able to find some examples that showed how to do this in XAML pretty quickly, but I spent a few cycles trying to get this to work with a DataGridColumn that I was adding programmatically. My first attempt looked like how you’d do it in XAML a-la new Binding("Price, Mode = BindingMode.Two-way”), but that didn’t work.

I decided to make up a fresh batch of coffee in the team french-press, and then it hit me: object initializers. A quick edit and I ended up with following:

var priceColumn = new DataGridTextColumn{ Header = "Price", Width = DataGridLength.Auto,
 Binding = new Binding("Price") { Mode = BindingMode.Two-way, UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged }};
ResultsGrid.Columns.Add(priceColumn);

This worked perfectly with the “Price” property I was binding to, since this was a property on one of our LINQ to SQL objects, and as such was raising the property-changed event for us in the generated code. When I went to do the same thing with another column (one not generated by the LINQ to SQL designer), I wasn’t seeing my edits reflected in my UI, but did see them in the domain objects via the debugger.

I had forgotten to raise the property-changed event in my ProposedPrice setter, so once I changed it to the following, everything worked great.

if (_proposedPrice != value)
{
SendPropertyChanging();
_proposedPrice = value;
SendPropertyChanged("ProposedPrice");
}