assign click event to a Button in a DataTemplate

Question

<Window x:Class="WpfApp12.MainWindow"
    xmlns=...usual namespaces...
    Loaded="Window_Loaded"
    >

<Window.Resources>

    <DataTemplate x:Key="myHeaderTemplate">
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="{TemplateBinding Content}"/>
            <Button Margin="5,0,0,0" x:Name="MyButton">Press me</Button>
        </StackPanel>
    </DataTemplate>

</Window.Resources>

<!-- Just point the datacontext to the code behind -->
<Window.DataContext>
    <Binding RelativeSource="{RelativeSource Mode=Self}"/>
</Window.DataContext>

<DataGrid Name="DG" ItemsSource="{Binding People}"/>

</Window>

This, togheter with the code behind below gives just what I want: a DataGrid with a column whose header has been dynamically assigned a DataTemplate with a Button "Press me":

The code behind:

public partial class MainWindow : Window
{

    public class Person
    {
        public string Name { get; set; }
        public string Surname { get; set; }
    }

    public MainWindow()
    {
        People.Add(new Person() { Name = "Isaac", Surname = "Newton" });
        People.Add(new Person() { Name = "Galileo", Surname = "Galilei" });

        InitializeComponent();
    }

    public ObservableCollection<Person> People { get; } = new ObservableCollection<Person>();

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        DG.Columns[0].HeaderTemplate = (DataTemplate)FindResource("myHeaderTemplate");
        //how to access the button in the template in order to assign the click event?
    }

    private void MyButton_Click(object sender, RoutedEventArgs e)
    {
        //DO SOMETHING
    }

  }
}

Now i want to dynamically wire MyButton_Click event to the button in the template.

This kind of problems seem to have a lot of coverage, this one being one of the best: WPF How to access control from DataTemplate There there is something like:

ComboBox myCombo =  _contentPresenter.ContentTemplate.FindName("myCombo", _contentPresenter) as ComboBox;

I'm not very familiar with the templating, and I cannot find the starting point, the "content presenter" on which to call the FindName.

To be honest, this implementation looks very weird to me and is simply doesn't fit the MVVM approach of WPF... — PythonNoob, Dec 06 '19 at 18:56
Actually, there is very little beyond adding a button to a header; the code is in the codebehind only for keeping things simple. The problem is how to connect the button, have you any idea? — AgostinoX, Dec 06 '19 at 23:39
Does this: https://learn.microsoft.com/de-de/dotnet/framework/wpf/data/how-to-find-datatemplate-generated-elements help you? — PythonNoob, Dec 07 '19 at 19:39

score 0 · Answer 1 · answered Dec 09 '19 at 13:27

You could use a recursive helper method that finds the Button in the visual tree:

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    DG.Columns[0].HeaderTemplate = (DataTemplate)FindResource("myHeaderTemplate");
    DG.Dispatcher.BeginInvoke(new Action(() =>
    {
        DataGridColumnHeadersPresenter presenter = FindVisualChild<DataGridColumnHeadersPresenter>(DG);
        DataGridCellsPanel dataGridCellsPanel = FindVisualChild<DataGridCellsPanel>(presenter);
        DataGridColumnHeader header = dataGridCellsPanel.Children[0] as DataGridColumnHeader;
        Button button = FindVisualChild<Button>(header);
        if (button != null)
            button.Click += MyButton_Click;
    }));
}

private void MyButton_Click(object sender, RoutedEventArgs e)
{
    //DO SOMETHING
}

private static T FindVisualChild<T>(DependencyObject obj) where T : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(obj, i);
        if (child != null && child is T)
            return (T)child;
        else
        {
            T childOfChild = FindVisualChild<T>(child);
            if (childOfChild != null)
                return childOfChild;
        }
    }
    return null;
}

assign click event to a Button in a DataTemplate

1 Answers1