Question

I have a List, a click event to Add a button, and a click event for each button created to show a Message.

public partial class MainWindow : Window
{
    List<Button> btnList = new List<Button>();

    public MainWindow()
    {
       InitializeComponent();
    }

    private void createbtn1_Click(object sender, RoutedEventArgs e)
    {
       Button btn = new Button();

       // wp is a WrapPanel in the MainWindow
       wp.Children.Add(btn);

       btn.Content = "Hello";
       btn.Click += hello_btn_Click;
       btnList.Add(btn);
    }

    private void hello_btn_Click(object sender, RoutedEventArgs e)
    {
       Button b = sender as Button;
       var bIndex = btnList.IndexOf(b);
       MessageBox.Show(bIndex.ToString());  
    }
}

Now the code is edited and runs OK.

Answer 1

It looks to me like you have 2 lists (btnLink and btnList), and are getting them confused:

btnLink.Add(btn);
...
var bIndex = btnList.IndexOf(b);