DataGrid columns do not refresh values with DataGrid2D

Question

I am trying to bind columns and rows of DataGrid to the same source but DataGrid does not show new value in the ColumnHeader when I change value in the RowHeader after TextBox lost focus. Headers collection contains new values as expected.

xmlns:dataGrid2D="http://gu.se/DataGrid2D"

<Grid>
    <DataGrid
        dataGrid2D:ItemsSource.RowHeadersSource="{Binding Headers}"
        dataGrid2D:ItemsSource.ColumnHeadersSource="{Binding Headers}"
        dataGrid2D:ItemsSource.Array2D="{Binding Items}"
        IsReadOnly="True"
        AutoGenerateColumns="True">
        <DataGrid.RowHeaderTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Value}" />
            </DataTemplate>
        </DataGrid.RowHeaderTemplate>
    </DataGrid>
</Grid>

DataContext:

public class MainViewModel
{
    public IEnumerable<Header> Headers { get; } = new Header[]
    { new Header { Value = "1" }, new Header { Value = "2" } };
    public string[,] Items { get; } = new string[2, 2] { { "1", "2" }, { "3", "4" } };
}
public class Header
{
    public string Value { get; set; }

    public override string ToString()
    {
        return Value;
    }
}

What I am doing wrong?

I am changing the Value property from the View side so it does not need INotifyPropertyChanged interface. If I call "Refresh" on DataGrid it updates but with blinking.

Edit:

Why are you downvoting me? Is it a bad question?

Answer 1

Here is one possible solution using the style for DataGridColumnHeader. I also explicitly used the Value property instead of the ToString method.

<Grid>
    <DataGrid
    dataGrid2D:ItemsSource.RowHeadersSource="{Binding Headers}"
    dataGrid2D:ItemsSource.ColumnHeadersSource="{Binding Headers}"
    dataGrid2D:ItemsSource.Array2D="{Binding Items}"
    IsReadOnly="True"
    AutoGenerateColumns="True">
        <DataGrid.Resources>
            <Style TargetType="{x:Type DataGridColumnHeader}">
                <Setter Property="ContentTemplate">
                    <Setter.Value>
                        <DataTemplate>
                            <TextBlock Text="{Binding Value}"/>
                        </DataTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </DataGrid.Resources>
        <DataGrid.RowHeaderTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Value, UpdateSourceTrigger=PropertyChanged}"/>
            </DataTemplate>
        </DataGrid.RowHeaderTemplate>
    </DataGrid>
</Grid>

You need to slightly change the ModelView then:

    public class Header: INotifyPropertyChanged
    {
        private string _Value;

        public string Value
        {
            get
            {
                return _Value;
            }
            set
            {
                _Value = value;
                OnPropertyChanged("Value");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string name)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(name));
            }
        }
    }