CODEWITHSUNDEEP
c#winforms
Lee
Lee

Reputation: 10603

c# second form closing after initialisation

I am trying to create a simple c# application (my first attempt at c# so please be kind). I've created a form with a textbox to capture an "auth code", which is then validated and then a webclient fetches an xml file passing this auth code in to the request. The data sent back is parsed e.c.t.

What i want to do is once the xml comes back and ive done my checks to valid it is all fine. I want to close the first form and load up a second form where i will programmatically add the form components needed to display the xml data in a pretty format.

My problem is that im unable to get the second form to stay open (im no doubt invoking the second form in the wrong manner). Here's what i have:

// close current form
this.Close();

//open new form
xmlViewForm xmlView = new xmlViewForm();
xmlView.Show();

I'm sure you've spotted the mistake im making by now. but just to state the obvious for the sake of completeness, it closes the first form, opens the second, and then immediately the program exits (the second form flashes up for a second obviously).

I've tried a few things but none of them work (including using Application.Run(new xmlViewForm()); instead of instantiating the class and using the show() method. Obviously you know that doesn't work, and now i do too, although i dont understand c# even remotely enough to work out why.

Thanks for any help :)

Upvotes: 1

Views: 1294

Answers (2)

KeithS
KeithS

Reputation: 71565

The first thing that came to mind is that you are closing the form that you opened by calling Application.Run(new MyForm()) or something similar. This form has special significance; it is the "main form" of the application, and when closed, it signals to the application that the user wants to close the entire program, no matter how many other windows are open.

There are two possible fixes. First, and easiest, is simply to Hide() the form you don't want visible instead of calling Close() on it. Though invisible, it's still running, so the application doesn't close.

The second solution is to define a custom "application context" that should be run instead of the "default context" that is created by specifying a main form to watch. You do this by deriving a custom class from System.Windows.Forms.ApplicationContext. With this context specified, you can use it to control termination of the application based on something other than closure of the main form. Example code that launches two "main forms" and keeps track of whether both are still active can be found at the MSDN page for the class. You can do something similar by specifying Load and Close handlers for the main form, then passing them to the child form when the main form instantiates it, thus keeping a count of "open" forms, and closing out the full application when that number is zero. Just make sure the child form loads before closing the main form by calling childForm.Show() before this.Close().

Upvotes: 5

Sean Vaughn
Sean Vaughn

Reputation: 3912

You can not open the second form after closing the main form.

Do this:

//open new form
xmlViewForm xmlView = new xmlViewForm();
xmlView.Show();

// hide current form
this.Hide();

Main form can not be closed because it's the parent form. The child form will never show up if you close the main form.

Or change the xmlViewForm to main form by editing Program.cs file

Application.Run(new XmlViewForm());

Then you can easily call the other form first at the time of loading and close it as you please:

private void XmlViewForm_Load(o, s)
{
    // hide current form, and this will remain hidden until the other form is done with it's work
    this.Hide();

    //open the other form
    TheOtherForm _theOtherForm = new TheOtherForm();
    _theOtherForm.Show();

}

private void TheOtherForm_Closed(o, s)
{
    // show current form
    this.Show;

}

Upvotes: 4

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