I’m know for, sometimes, miss the tinny picture, i.e., the details… By rushing into things without proper first reading.

My code is exactly the one here. I’ve created a new C# project, copy and pasted your code into it and run it. In fact I was surprised it didn’t work, since I’ve seen no reason for it to fail… Until now. Now I see what I’ve missed. :S It’s supposed to be used with regular forms… duh!

Thanks! As I said before, this is truly a cool implementation and it can provide me a way for getting rid of all my Singleton forms… I’ll put it to a good test.

There isn’t any reason for it not to work under .NET 3.5, that I can see. What’s the exact problem you’re seeing?

You are correct, you don’t inherit from the Singleton object, your Forms shouldn’t be ‘Singleton objects’. You simply use the class’ GetInstance method to create singleton instances of forms for you.

Feel free to paste your code if you are having trouble.

David

This is cool! But it doesn’t work in .NET 3.5 (C#). Keeps saying that the constructor of SomeSingletonForm can’t be found It only works with a public constructor. Am I doing something worong?

public static class SingletonFormProvider
{
#region Singleton
// Explicit static constructor to tell C# compiler
// not to mark type as beforefieldinit
static SingletonFormProvider()
{
}
#endregion

static Dictionary mTypeFormLookup = new Dictionary();

static public T GetInstance()
where T : Form
{
return GetInstance(null, new Type[]{ } /*sin parámetros*/);
}

static public T GetInstance(Form owner)
where T : Form
{
return GetInstance(owner, new Type[] { }) /*sin parámetros*/;
}

static public T GetInstance(Form owner, params object[] args)
where T : Form
{
// ¿Ya hay una instancia del tipo T?
if (mTypeFormLookup.ContainsKey(typeof(T)))
{
T f = (T)mTypeFormLookup[typeof(T)];

// ¿Esa instancia está disposed?
if (f.IsDisposed)
{
// Borro para la entrada correspondiente al tipo typeof(T) la instancia (formulario) f, puesto que está disposed.
mTypeFormLookup.Remove(f.GetType());
}
}

// ¿No hay instancia de tipo T?
if (!mTypeFormLookup.ContainsKey(typeof(T)))
{
// Constructor de la clase T con parámetros args.
ConstructorInfo constructorInfo =
typeof(T).GetConstructor(args.Select(p => p.GetType()).ToArray());

Debug.Assert(constructorInfo != null,
string.Format(”La clase {0} no tiene ningún constructor disponible.”,
typeof(T)));

// Equivale a: T f = new T(…, [args], …);
Form f = constructorInfo.Invoke(args) as T;
#if DEBUG
if (f == null)
{
object[] obj = constructorInfo.GetParameters().Select(p => p.Name).Cast().ToArray();
StringBuilder sb = new StringBuilder();
int i = 0;
foreach (string param in constructorInfo.GetParameters().Select(p => p.Name))
{
sb.Append(param);
sb.Append(”=”);
sb.Append(args[i++]);
if (i < args.Length) sb.Append(”, “);
}

Debug.Assert(f != null,
string.Format(”No se ha podido invocar el constructor {0} de la clase {1} con parámetros ({2}).”,
constructorInfo.Name, typeof(T), sb.ToString()));
}
#endif
// Añado para la entrada correspondiente al tipo typeof(T) la instancia (formulario) f.
mTypeFormLookup.Add(typeof(T), f);
f.Owner = owner;
}

return (T)mTypeFormLookup[typeof(T)];
}
}

But, i have a question. I have the following code:

static class Program
{
///
/// The main entry point for the application.
///
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(MenuPrincipalObservador.InitForm());
}
}

class MenuPrincipalObservador
{

private MenuPrincipalObservador()
{
}

public static Form InitForm()
{
MenuPrincipalObservador mpo = new MenuPrincipalObservador();

MDIParent1 mdi = MenuPrincipalFormSingleton.Instance.createForm();

mdi.BtnRecepcioMercaderiesClicked += mpo.ClickRecepcioHandler;

return mdi;
}

private void ClickRecepcioHandler(Object sender, EventArgs e)
{
frmRecepcioMerc frm = SingletonFormProvider.GetInstance(iDontKnow);
frm.Show();
}
}

In the last function ClickRecepcioHandler, like him shipment the owner?

Thanks for your attention.