CODEWITHSUNDEEP
c#winforms
IEnumerable
IEnumerable

Reputation: 3790

Is there a better way to check if a form is loaded?

I have 2 Forms in my app, Form1 and Form2. I want to know if there is a better way of checking if the form has already been loaded. If the form is loaded in memory and visible, I want the button to do nothing, if the User has closed the form it should re-instantiate it.

For more info check my code or comment.. :)

public partial class Form1: Form
{
    private Form2 form2;

    public Form1() {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e) {

        if (form2== null) {
            form2= new Form2();
        } else {
            if (form2.has_exited()) { // this is a private property
                                      // that I set when Form2.Closing executes
                form2.Dispose();
                form2= new Form2();
            }
        }
        form2.Show();
    }
}

Upvotes: 0

Views: 5146

Answers (4)

DerMike
DerMike

Reputation: 16190

I'd use

if (form2 == null)
{
    form2 = new Form2();
    form2.FormClosed += (s, e) => { this.form2 = null; };
    form2.Show();
}
form2.BringToFront()

So every time form2 is closed, the reference is set to null. Next time it can be re-instantiated.

As long as it is still there, bring it to front.

Upvotes: 3

Servy
Servy

Reputation: 203820

You don't need to have Form2 handle the closing event, you can just do it directly from Form1:

private Form2 form2;

private void button1_Click(object sender, EventArgs e)
{
    if (form2 == null)
    {
        form2 = new Form2();
        form2.FormClosed += (_, arg) =>
        {
            form2 = null;
        };
        form2.Show();
    }
    else
    {
        //the other form has been opened and not closed; not sure what you want to do
    }
}

Also note that if a form is shown via Show you don't need to dispose of it. If you show it via ShowDialog then you do, but when you use the non-modal dialog the system will automatically attach an event handler to the closing event that calls dispose.

Upvotes: 6

Haedrian
Haedrian

Reputation: 4328

If you're showing the form, the form will thrown an event called Form.Shown

http://msdn.microsoft.com/en-us/library/system.windows.forms.form.shown.aspx

You can put some sort of handling code there (even if its just setting a flag). Similarly there's a form closing/closed event if the user closes it.

I THINK there's a formloaded event too, but I can't remember off the top of my head.

Upvotes: 0

AD.Net
AD.Net

Reputation: 13399

You can pass Form1 to Form2 and in the events like .Loaded or while disposing/exiting in the Form2, you can use the Form1 object to let it know that those events have happened.

Upvotes: 0

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