Develop Reference

How to correctly close a c# form

I am currently working with a c# desktop application that is connected to a web service. In one of the forms, I want to close form when the back button is clicked. I have done it like this:
private void bBack_Click(object sender, EventArgs e)
{
//this.Hide();
this.Close();
frmMain fMain = new frmMain();
fMain.MdiParent = this.MdiParent;
fMain.Show();
}
When I use this.Hide(), it seems like the form I want to close still runs in the background, thus still contacting the web service.
When I use this.Close(), the form seems to close and no contact to the web service is made, but my desktop application suddenly goes full screen and frmMain is opened in a new window.
I have read the documentation displayed here, but I could not find anything useful.

Hide does just that, it hides it, its still there.
So yes, you would need to close it, however, if you close it before you make the next, theres a chance that the code exits there and isnt completing any follow on code.
Rearranging your code to
frmMain fMain = new frmMain();
fMain.MdiParent = this.MdiParent;
fMain.Show();
this.Close();
Should work

C# - Don't bring form to front

My apps use a timer that display a form after some seconds.
When I minimize my apps to do other stuff, the timer is still active (I'm ok with that) and the form bring to front over all my windows with focus on it (normal behavior).
I want that the new form open above my main apps but not above all my windows.
In the main form, I call the new form like this :
MRIS.EVENT_BOX form1 = new MRIS.EVENT_BOX();
form1.Owner = this;
form1.ShowDialog();
I manage to remove the focus problem by adding this in the EVENT_BOX :
protected override bool ShowWithoutActivation { get { return true; } }
I also check that TopMost is set to false in the new form.
But the new form is still show above all the others (without focus this time...).
I check some other questions but cannot manage to find something useful.
Some people talk about visible form ?
If you can help me ?
Thanks

You need to call form1.Show(); if you don't want to bring it to front
form1.Show();
//form1.BringToFront() You may need to call this if you want to being it to front
form1.ShowDialog() shows the form as dialog which means it will be shown on top of parent form. You can check more details on this here

Windows Forms: upon start, load but hide form

I'm creating a System Tray application. Upon initializing the app, I want to:
Initialize and load a form so it runs in the background
But keep the form hidden (until the user doubleclicks the tray icon)
It is important that the form is loaded and runs in the background, because the form contains an embedded browser that will initialize a web socket connection to receive data. But it needs to be hidden. I tried solving this by playing with the Visible property of the form. So far, I have this (only relevant code shown):
public TrayApp()
{
var ni = new NotifyIcon();
InitializeForm();
ni.DoubleClick += this.ShowForm;
}
private void InitializeForm()
{
//load the form in the background so it can start receiving incoming data, but don't actually show the form
myForm = new MyForm();
myForm.Show();
myForm.Visible = false;
}
private void ShowForm(object sender, EventArgs e)
{
myForm.Visible = true;
}
This works quite well, except for one small detail: upon starting the app, I briefly see the form flashing before it is hidden. I suppose the Show method also sets the Visible flag to true, causing the flash to occur.
Other things I tried, based on comments:
Do not call myForm.Show(), only initialize the form. This avoids the flash but won't load the browser and hence the websocket connection is not initialized
Do myForm.Hide(): same effect as previous
Set Opacity to 0 before calling Show() and set it to 1 after setting Visible to false: this actually works, but I was hoping for a cleaner solution
How to avoid the flash and keep the form running but hidden?

You could try to set the hide property before you show your form.
myForm = new MyForm();
myForm.Visible = false;
myForm.Show();

You could try to write a function that initializes the socket. Put this function inside your MyForm class and call it from inside the InitializeForm().
Hope this helps.

How to know if the Form App open or not c#

Does anyone know how can I know if the Windows Form Application (C#) is open or that the client closed it?
(In my App I have a Windows Form Application (Form1) that allow the user to open another Forms (Form2). I want to know if the Form2 is open or close.)
I need to know that because I run the Form2 from a thread, and I want to make the thread runnig until the user close Form2.
Many thanks!

You can check if a form of a given type is open in your application like this (using LINQ):
if (Application.OpenForms.OfType<Form2>().Count() > 0)
{
// there is an instance of Form2 loaded
}

You need to elaborate on your question a bit more. Are you talking about monitoring the application from another application? Or that one form needs to know if another one is open? Or a form needs to know when another form closes?
There are a couple of ways to monitor forms closing within the same application.
Calling ShowDialog() on your form instead of Show() will ensure that code following the ShowDialog() call doesn't get executed until the user closes the form.
The Form class has a Visible property, which returns true/false depending on whether the form is visible or not.
As for the application itself, there is an ApplicationExit event on the static Application class which gets called just before the application closes so you could listen to that event if, for example, you need to perform some clean-up on exit.

If you want to run only single instance of application, check this link.
There you will also see how to check whether a process is still active.

If you mean MDI application with its child forms:
private Dictionary<Type, Form> SingleInstanceForms = new Dictionary<Type, Form>();
public Form ActivateForm<T>() where T : Form, new()
{
Cursor.Current = Cursors.WaitCursor;
if (!this.SingleInstanceForms.ContainsKey(typeof(T)))
{
T newForm = new T();
//setup child
newForm.MdiParent = this;
newForm.WindowState = FormWindowState.Maximized;
//newForm.Icon = Icon;
newForm.FormClosed += new FormClosedEventHandler(delegate(object sender, FormClosedEventArgs e)
{
this.SingleInstanceForms.Remove(sender.GetType());
});
this.SingleInstanceForms.Add(typeof(T), newForm);
newForm.Show();
this.Refresh();
}
Form formToActivate = this.SingleInstanceForms[typeof(T)];
formToActivate.Activate();
Cursor.Current = Cursors.Default;
return formToActivate;
}
this will create the form child if hasn't been created yet and activate it if it has been created.
sample: ActivateForm<dlgChildOne>();

restart Function in visual C#

I have a windows application I need to create a button that unload/close/restart the currunt form while its running and reload/reopen/restart the same form.
How ??
I tried the hide show thing but it keeps the old form running in the background

Application.Restart();
I found it ....

Application.Restart() will restart your entire application.
Hide() will only do what it says, hide the form. If you just want a fresh version of your form to reappear, you can just create a new one, Show() it, and Close() your current form.
public void Restart()
{
var window = new MyForm();
window.Show();
this.Close();
}
You'll have 2 forms open for a very short time, so if you have any data connections that need to be closed, do so before reopening the form. To the end-user, it will happen so fast that they won't know 2 forms were open.