PreviewKeyDown with System.Diagnostics.Process.Start(some url) opens two browsers

Question

In this question (and accepted answer) a simple WPF program sets up a PreviewKeyDown handler to call Process.Start on a directory name to open that folder in Windows File Explorer.

If I change the handler definition to open up a URL as follows:

data_grid.PreviewKeyDown += (s, e) =>
{
    if (e.Key == Key.O && data_grid.SelectedItem is DirectoryInfo info)
        System.Diagnostics.Process.Start("https://www.github.com");
};

it opens up two browser tabs when I press the o key.

The original version did not open two File Explorer windows.

Why does the URL version open two browser windows? What's a good way to get it to only open one?

To make this concrete and more explicit, here's an entire program which demonstrates the issue.

MainWindow.xaml:

<Window x:Class="WpfUrlsDataGrid.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfUrlsDataGrid"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>

    </Grid>
</Window>

MainWindow.xaml.cs:

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace WpfUrlsDataGrid
{
    public class Address { public string Url { get; set; } }

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

            var data_grid = new DataGrid()
            {
                IsReadOnly = true,
                AutoGenerateColumns = true,
                ItemsSource = new[] 
                {
                    new Address() { Url = "https://www.google.com" },
                    new Address() { Url = "https://www.github.com" },
                    new Address() { Url = "https://www.stackoverflow.com" }
                }
            };

            data_grid.PreviewKeyDown += (s, e) =>
            {
                if (e.Key == Key.O && data_grid.SelectedItem is Address address)
                    System.Diagnostics.Process.Start(address.Url);
            };

            var dock_panel = new DockPanel();

            dock_panel.Children.Add(data_grid);

            Content = dock_panel;
        }
    }
}

Here's what the example program looks like:

UPDATE in response to comments below

If I add a breakpoint at the following line:

System.Diagnostics.Process.Start(address.Url);

Only one browser tab opens! Very strange that the behaviour is different when debugging.

UPDATE in response to comments below

If I change the browser that is used to Microsoft Edge as follows:

System.Diagnostics.Process.Start(String.Format("microsoft-edge:{0}", address.Url));

it still opens up two tabs.

UPDATE

The issue seems to be intermittent. Most of the time, it opens two browser tabs. However, occasionally it will open only one tab.

Use the debugger and see if your function is called twice by setting a breakpoint there — Denis Schaf, Apr 11 '19 at 05:17
Also check if this changes when you change your standard browser to a different browser just to make sure its not the browser trying to open a start-page or something like that — Denis Schaf, Apr 11 '19 at 05:27
Hi @DenisSchaf! Thanks for taking a look. I've added some updates to the question in response to your comments. — dharmatech, Apr 11 '19 at 05:57
I tested and it works for me . it opens only one window. Is it something wrong with keyboard ? May be sending many 2 keystrokes instead of 1? Try using some other key instead of o maybe? i once had this problem with printscreen key. Just one keypress sent 5 keystrokes. So try to change the keyboard? — na th, Apr 11 '19 at 09:03
@nath The issue occurs both with the external keyboard as well as the laptop keyboard. — dharmatech, Apr 11 '19 at 16:57
@HansPassant Thanks for the reference. It looks like in your answer there, you're using a `BeginInvoke` that's part of Windows Forms. The demo app above is in WPF. Is there a good an equivalent of `BeginInvoke` for WPF? — dharmatech, Apr 12 '19 at 01:42

score 1 · Answer 1 · answered Apr 11 '19 at 08:32

1

data_grid.PreviewKeyDown += (s, e) =>
{
    if (e.Key == Key.O && data_grid.SelectedItem is DirectoryInfo info)
        System.Diagnostics.Process.Start("https://www.github.com");
    **e.Handled = true;**
};

answered Apr 11 '19 at 08:32

user11344985

11
1

Hmm... So, with this approach, it does seem to eliminate the double browser tab issue! However, the 'up' and 'down' arrow keys no longer change the current selected row. – dharmatech Apr 11 '19 at 17:02
A slight modification of this approach seems to work! I've added an answer based on this approach. – dharmatech Apr 11 '19 at 17:08

dharmatech · Answer 2 · 2019-04-12T01:37:10.690

0

This approach seems to resolve the issue:

data_grid.PreviewKeyDown += (s, e) => 
{
    if (e.Key == Key.O && data_grid.SelectedItem is Link link)
    {
        System.Diagnostics.Process.Start((data_grid.SelectedItem as Link).Url);

        e.Handled = true;
    }
};

Note that it's a slight modification of the answer by @user11344985. It moves the e.Handled = true; line into the if body.

edited Apr 12 '19 at 01:37

answered Apr 11 '19 at 17:07

dharmatech

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PreviewKeyDown with System.Diagnostics.Process.Start(some url) opens two browsers

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