Question

I want to bind a datagrid view in a user control that is docking to a main WPF form. However everytime I try to bind the data it must pre exist and won’t update. Is there a way to perform this in the XAML directly to know when an event is triggered to update the datagridview rather than do it in the code behind?

Partial code of XAML:

xmlns:c="clr-namespace:TestWPFMain"

<UserControl.Resources>
    <c:GridData x:Key="dataforGrid"/>
</UserControl.Resources>
<Grid>
    <DataGrid Grid.Row="2" x:Name="datagridMain" ItemsSource="{Binding Source={StaticResource dataforGrid}, Path=Results, Mode=TwoWay}" />
</Grid>

Code Behind for UserControl above:

public GridControl()
    {
        InitializeComponent();

        GridData gd = new GridData();
        gd.UpdateResults();

        //datagridMain.ItemsSource = gd.Results;  
        -- This code above will work if I uncomment but I want it to be bound 
           directly and was curious as I thought the mode of 'two way' would 
           do this.  I am not certain and most examples assume property is already
           set up and not being created and updated.
    }

Code Class for GridData:

class PersonName
{
    public string Name { get; set; }
}

class GridData
{
    public ObservableCollection<PersonName> Results { get; set; }

    public void UpdateResults()
    {
        using (EntityDataModel be = new EntityDataModel())
        {
            var list = be.tePersons.Select(x => new PersonName { Name = x.FirstName });

            Results = new ObservableCollection<PersonName>(list);
        }
    }
}

Answer 1

To use binding like this, you need to:

1. Set the DataContext correctly on the DataGrid (or on one of its parent)
2. Implement INotifyPropertyChanged on your model class, and raise PropertyChanged in the property setter.

1)

Set your window’s DataContext to the GridData object:

public GridControl()
{
    InitializeComponent();

    GridData gd = new GridData();
    gd.UpdateResults();
    this.DataContext = gd;
}

2)

Implement INotifyPropertyChanged. This ensures that your view gets notified when the Results property gets updated:

public class GridData : INotifyPropertyChanged
{
    private ObservableCollection<PersonName> _results;
    public ObservableCollection<PersonName> Results 
    {  
        get { return _results; }
        set
        {
            _results = value;
            RaisePropertyChanged("GridData");
        }
    }

    // ...

    #region INotifyPropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;
    private void RaisePropertyChanged(string prop)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }
    }
    #endregion
}

Then you can simply bind to the path relative to the data context.

<DataGrid ItemsSource="{Binding Results}" />

Note that you don’t need two-way binding in this case — that’s for propagating changes from the View back to your model (ie, most useful for when there’s a UI control like a text box or checkbox).