Triggering event when mouse is clicked once

Question

I have a code that triggers a messagebox when I click on a node in a treeview. Problem is, it only triggers when I click twice. Not the well known double click but I mean two clicks have to happen. I could click once, wait 5 minutes and click again and then messagebox pops up. Is there a way that I could alter my code to show the messagebox when I click once instead of twice? This is what I have as my current code:

if (e.Button == MouseButtons.Left)

            {

                string NodeName = treeSidebar.SelectedNode.Text;

                foreach (KeyValuePair<string, string> kvp in RSS.list)

                {

                    string name = kvp.Key;

                    string url = kvp.Value;

                    if (NodeName == name)

                    {

                        MessageBox.Show(url);

                    }

                }

            }