[1.0/1.1] Checking whether the form is disposed or not!

[pvbangera]

On a mdi's menu click i am calling a child form.

On the click event I want to check whether the form is already initiated. if not then i want to initiate it first and then call the show method. on closing the form i dispose it.

How to chk whether the form is disposed or not?

IsNothing is not working

[jmcilhinney]

I'm not sure whether you have resolved this or not but the code should look something like this:

private Form2 childForm;
 
private void ShowChildForm()
{
    if (this.childForm == null || this.childForm.IsDisposed)
    {
        // Create a new child form and show it.
        this.childForm = new Form2();
        this.childForm.MdiParent = this;
        this.childForm.Show();
    }
    else
    {
        // Activate the existing child form.
        this.childForm.Activate();
    }
}

Note that if there is not supposed to be more than one instance of a form then you can also have that form implement the Singleton pattern:

public partial class Form2 : Form
{
    private static Form2 _instance;
 
    public static Form2 Instance
    {
        get
        {
            if (_instance == null || _instance.IsDisposed)
            {
                _instance = new Form2();
            }
 
            return _instance;
        }
    }
 
    private Form2()
    {
        InitializeComponent();
    }
}

Then your code in the parent form becomes:

private void ShowChildForm()
{
    Form2.Instance.MdiParent = this;
    Form2.Instance.Show();
    Form2.Instance.Activate();
}