利用WindowsFormsApplicationBase的IsSingleInstance来控制应用程序只能单实例运行。
[DllImport("user32.dll", EntryPoint = "ShowWindow", CharSet = CharSet.Auto)]
public static extern int ShowWindow(IntPtr hwnd, int nCmdShow);
[DllImport("User32.dll")]
private static extern bool SetForegroundWindow(IntPtr hWnd);
static SingleInstanceManager manager;
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main(string[] args)
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
manager = new SingleInstanceManager(new Form5());
manager.Run(args);
}
public static void ShowForm(Form Nform, bool closeOldOne = true)
{
manager.ChangeForm(Nform, closeOldOne);
}
public class SingleInstanceManager : WindowsFormsApplicationBase
{
ApplicationContext app;
public SingleInstanceManager(Form mainForm)
{
this.IsSingleInstance = true;
app = new ApplicationContext();
app.MainForm = mainForm;
}
protected override bool OnStartup(Microsoft.VisualBasic.ApplicationServices.StartupEventArgs e)
{
Application.Run(app);
return false;
}
protected override void OnStartupNextInstance(StartupNextInstanceEventArgs eventArgs)
{
base.OnStartupNextInstance(eventArgs);
SetForegroundWindow(app.MainForm.Handle);
ShowWindow(app.MainForm.Handle, );
}
public void ChangeForm(Form newForm, bool closeOldOne = true)
{
if (app.MainForm == newForm) return;
Form tem = app.MainForm;
tem.Hide();
app.MainForm = newForm;
newForm.Show();
if (closeOldOne) tem.Close();
}
}单实例的类中有一个变量ApplicationContext，应用程序线程的上下文，这个变量是为了切换窗口而设计的。具体实现代码看下面的ChangeForm。
调用时，例如上面的Form5中有一个按钮，打开新窗口Form6，则：
private void button1_Click(object sender, EventArgs e)
{
Program.ShowForm(new Form6());
}
只需要这样调用就能够切换窗口，关闭Form5，节约资源。