One of the things I needed to do at an MDI application I was involved with was the ability to only load a specific form once, and make sure it does not load again. That form could not be modal, but could only have one instance running inside the MDI parent. I came up with a rather elegant solution, if I do say so myself :)
(Of course what usually happens when I come up with an “elegant” solution is that someone shows me a simple property on the form that says something like "AllowOneInstanceOnly" which does exactly what I did here. )
How to call this class:
In your MDI form, simply write this:
MdiFormLoader.LoadFormType(typeof(CustomerDetailsForm), this);
using System;
using System.Windows.Forms;
using System.Collections.Specialized;
namespace UI.Utilities
{
public class MdiFormLoader
{
private static HybridDictionary m_InitializedForms = new HybridDictionary();
public static void LoadFormType(Type formType, Form mdiParentForm)
{
if (IsAlreadyLoaded(formType))
{
return;
}
FlagAsLoaded(formType);
Form frm = (Form)Activator.CreateInstance(formType);
frm.MdiParent = mdiParentForm;
frm.Closed += new EventHandler(FormClosed);
frm.Show();
}
private static void FlagAsLoaded(Type formType)
{
m_InitializedForms[formType.Name] = true;
}
private static void FlagAsNotLoaded(Type formType)
{
m_InitializedForms[formType.Name] = false;
}
private static bool IsAlreadyLoaded(Type formType)
{
return ((m_InitializedForms[formType.Name] != null) &&
(bool)m_InitializedForms[formType.Name] == true);
}
private static void FormClosed(object sender, EventArgs e)
{
Form closingForm = (Form)sender;
closingForm.Closed -= new EventHandler(FormClosed);
FlagAsNotLoaded(sender.GetType());
}
}
}