How to assign an event handler for DataTemplate in code?

Question

I try to dynamically create and assign a DataTemplate to a HeaderTemplate of DataGrid through code. To do this I have a method GetDatatemplate(string fromstring) that defines an XML literal and then uses this to create a DataTemplate. This works fine as long as I don't include the MouseLeftButtonDown event handler in the DataTemplate.

My DataTemplate saved in string variable called StringHeaderTemplate in code-behind of MainWindow.xaml.cs:

private string StringHeaderTemplate =@"

And the method which gets DataTemplate:

private DataTemplate GetDatatemplate(string fromstring)
{
    ParserContext context = new ParserContext();
    context.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
    context.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
    return  (DataTemplate)XamlReader.Parse(fromstring, context);
}

Then I just apply this DataTemplate to HeaderTemplate of DataGrid:

private void dg_AutoGeneratingColumn_1(object sender, DataGridAutoGeneratingColumnEventArgs e)
{
    DataTemplate dtCell = null;
    DataTemplate dtHeader = null;
    string dtString = string.Empty;
    string dtHeaderString = string.Empty;
    switch(Type.GetTypeCode(e.PropertyType))
    {
        case TypeCode.String:
        dtString = StringTemplate.Replace("xxColumnxx", e.PropertyName);
        dtHeaderString=StringHeaderTemplate;
        break;
    }
    if(!string.IsNullOrEmpty(dtString))
    {
        dtCell = GetDataTemplateForDataGrid(dtCellString);
        dtHeader = GetDataTemplateForDataGrid(dtHeaderString);
        DataGridTemplateColumn c = new DataGridTemplateColumn()
        {
          CellTemplate = dtCell,
          HeaderTemplate = dtHeader,
        };
        e.Column = c;            
     }
}

The event handler is really simple:

private void Grid_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
   MessageBox.Show(DateTime.Now.ToString());         
}

The exception I get is a XamlParseException that has an InnerException of type ArgumentException that says:

"Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type."

Any ideas what to do?

Update:

I've tried to bind through Command, however the CallSortingCommand is not called. Maybe you know what I am doing wrong?

Anton Danylov · Accepted Answer

It is an interesting problem, 'cause possible solution could be in finding object you want to subscribe to in visual tree, after data template is applied. But it is a column and it would be hard to access visual tree in that case.

I'd suggest to go with Interactions, that allow to define event triggers in XAML. Please have a look at the code below:

    private string StringHeaderTemplate = @"

P.S. Please pay attention to public access modifier of Grid_MouseLeftButtonDown event handler, with private it will not work.

UPDATE

Full source code:

XAML

C#

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        DataContext = new MainWindowViewModel();
    }


    private string StringHeaderTemplate = @"

How to assign an event handler for DataTemplate in code?

Answers (1)

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