在没有API的情况下将已打开的winform应用程序带到前面？

Question

Hi,

Say that we got a WinForm application(app1) running in the background, now another application(app2)(the topmost active application) trigger a startProcess with the app1.

Now I need app1 to use the existing instance and bring it to topmost application(not only within the app1 application).

I have found this : http://sanity-free.org/143/csharp_dotnet_single_instance_application.html

Is it true that its not possible to do this without API? I have looked att bringToFront, Activate and Focus but all these does seem to only effect within a application and not between applications?

Answer 1

I don't know what you mean "without API" or why that matters.

However the simplest way is via WindowsFormsApplicationBase . It gives you all you need, with just a few lines of code.

You need to add a reference to the Microsoft.VisualBasic assembly - but it can be used through C#.

Make this class:

public class SingleInstanceApplication : WindowsFormsApplicationBase
{
    private SingleInstanceApplication()
    {
        IsSingleInstance = true;
    }

    public static void Run(Form form)
    {
        var app = new SingleInstanceApplication
        {
            MainForm = form
        };

        app.StartupNextInstance += (s, e) => e.BringToForeground = true;

        app.Run(Environment.GetCommandLineArgs());
    }
}

And in your Program.cs, change the run line to use it:

//Application.Run(new Form1());
SingleInstanceApplication.Run(new Form1());

Answer 2

You really need some sort of communications between 2 apps. In article link to you posted communications is through WinApi messages. Also you can do that through sockets or through files and FileWatchers.

UPD1: Code to simulate minimize with timer simulation message from another app and maximize on that message:

public partial class Form1 : Form
{
    private Timer _timer = null;

    public Form1()
    {
        InitializeComponent();

        this.Load += OnFormLoad;
    }

    private void OnFormLoad(object sender, EventArgs e)
    {
        Button btn = new Button();
        btn.Text = "Hide and top most on timer";
        btn.Width = 200;
        btn.Click += OnButtonClick;

        this.Controls.Add(btn);
    }

    private void OnButtonClick(object sender, EventArgs e)
    {
        //minimize app to task bar
        WindowState = FormWindowState.Minimized;

        //timer to simulate message from another app
        _timer = new Timer();
        //time after wich form will be maximize
        _timer.Interval = 2000;
        _timer.Tick += new EventHandler(OnTimerTick);
        _timer.Start();
    }

    private void OnTimerTick(object sender, EventArgs e)
    {
        _timer.Stop();

        //message from another app came - we should 
        WindowState = FormWindowState.Normal;
        TopMost = true;
    }
}