WPF outsourcing company-technology sharing WPF only runs one instance

First, reference Microsoft. VisualBasic
Create a class single
Public class single: Microsoft. VisualBasic. applicationservices. windowsformsapplicationbase
{
APP;
Public single ()
{
This. issingleinstance = true;
}
Protected override bool onstartup (Microsoft. VisualBasic. applicationservices. startupeventargs eventargs)
{
A = new app ();
A. initializecomponent ();
A. Run ();
Return false;
}
Protected override void onstartupnextinstance (Microsoft. VisualBasic. applicationservices. startupnextinstanceeventargs eventargs)
{
Base. onstartupnextinstance (eventargs );
A. Activate ();
}
}

App. CS
Public partial class app: Application
{
Protected override void onstartup (startupeventargs E)
{
Base. onstartup (E );
Window1 W = new window1 ();
W. Show ();
}
Public void activate ()
{
Mainwindow. Activate ();
}
Private void application_sessionending (Object sender, sessionendingcanceleventargs E)
{

}
Private void application_startup (Object sender, startupeventargs E)
{

}
Private void application_exit (Object sender, exiteventargs E)
{

}
}
App. G. CS
[System. stathreadattribute ()]
[System. Diagnostics. debuggernonusercodeattribute ()]
Public static void main (string [] ){
Single S = new single ();
S. Run ();
}