open file with a running process
<p>I am making an application that can open a custom document. I connected the document extension to the application (using registry), but when I open the document, it is always opened with a new instance of the application.</p>

<p>I want some logic that can open a document running the current process if it exists. I dont mean a single instance. It should be able to run by multiple instances. Like IE or chrome, it should be able to open an HTML file with tab when the process is running, but it can also run a new instance.</p>

<p>How can I do it?</p>
