Develop Reference

"Include" instead of ShowDialog()

I'm trying to make a WindowsFormApplication in Visual Studio 2015 and need some help.
I've been trying to search for the answer on internet but can find out how to do the following:
I have two windows (solutions?). I open the second window with a button in the first one with this code:
this.Hide();
intermec prodinter = new intermec();
prodinter.ShowDialog();
My question is:
How can i "include" the second window (like "include" in PHP) instead of close the first window and then open the next one, like it does now?

A Form is just another Control. Think of it as a Container (because it holds other Controls).
A User Control can also hold more than one Control. There are ways you can display a Window inside another Window in a WinForms app, but the desired effect is not always guaranteed. So it would be best to place all of your controls (for "page 1", for example) in a User Control called "Page1", and then, when appropriate, add that User Control to the Form, and set its Dock property to Fill.
And when it's time to show a different "page", Hide(); "Page1", and Show(); "Page2".

I think you are talking about form inheritance:
Just create a form, lets call it as frmBase. And add some controls onto frmBase which you want to have on other forms as well.
Create other form, lets call it as frmDerived.
In the code behind of frmDerived, just do the following:
// derive the frmDerived form from frmBase
public partial class frmDerived : frmBase
{
public frmDerived()
{
InitializeComponent();
}
}
And then just check the frmDerived form design, it should include everything from frmBase.
And you may want to make the access modifier of some controls of frmBase to Public as required to access them on frmDerived.
I hope this will help you. :)

Winform app, force execute OnLoad Event when focus is on another tab

I have a WinForm app, the form has TabControl, control has three tabs tabPage1,tabPage2,tabPage3.
The Tab 'tabPage3' is hosting a User defined control which internally has one or more child controls.
Now my problem lies in tabPage3,
I know it is a pure Winforms behavior, until your parent is not activated child controls Onload event won't fire.
I have a requirement to force the Onload event to fire when the focus is on tabPage1, tabPage2. Is there any way to force the Onload event to fire.
I have already visited following links but didn't find any clue. Link Link Link

This is a very unusual requirement, strongly smells like an XY problem. The Load event is heavily over-used in Winforms, a side-effect of it being the default event for a Form or UserControl. One of the behaviors inherited from VB6, the Load event was a big deal in that language. What you want can easily be accomplished by not giving Winforms a choice:
public UserControl3() {
InitializeComponent();
CreateHandle();
}
The CreateHandle() call does the forcing, OnLoad will immediately run. But do be aware that this happens very early, too early to do the kind of things that you'd really want to use OnLoad() or the Load event for. Which are rather limited, it is only truly necessary to discover the actual Location and Size of the control. Anything else belongs in the constructor. Surely including the code that you now run in OnLoad().
Strongly favor using the constructor instead.

I had a similar problem for a previous project, for my needs I managed to just iterate over every tab page in the forms constructor (or possibly OnLoad I can't remember) and then reset the index back to 0 before ever showing the end user.
Something similar to:
for(int i = 1; i < tabControl.TabCount; i++)
tabControl.SelectTab(i);
tabControl.SelectTab(0);

What is the most efficient way to create a Win form with multiple pages?

My goal
I am working on a project in C# using Visual Studio 2013. The project is one that I intend to contain a lot of pages. These pages are all linked together using buttons. My problem is that I cannot come up with an efficient and elegant solution for this.
My attempts
So far I have came up with two potenial solutions to my problem. First I added extra forms and then on button press I hid the current form and displayed the new form, like so:
Form2 frm = new Form2();
frm.Show();`
Form1.Hide();
While this does work, I have two problems with it.
My project will end up with hundreds of forms
The transition between forms looks sloppy. I am aiming for a browser like transition by where all navigation occurs on one window, without opening and closing others.
The second potential solution I tried incorporated the use of Panels. So I essentially created each page on a different Panel. Then the appropriate panel was shown upon a button press and the rest were hidden. Like this:
private void button1_Click(object sender, EventArgs e)
{
mainMenuPanel.Hide();
submenuPanel1.Show();
submenuPanel2.Hide();
submenuPanel3.Hide();
submenuPanel4.Hide();
}
This is exactly what I was looking for however my issue with it is that managing the vast amount of panels quickly became a nightmare. Editing the controls on a Panel that was hidden behind 9 other Panels and as the number of panels in my project was only going to grow - this does not seem like the ideal solution in its current form.
In my head I thought there maybe an option in Visual Studio 2013 that allows me to 'hide' the Panels I am not using on the form, or drag them off the form temporarily. Is that an option in Visual Studio.
If not do any of you know a more efficient and manageable way of achieving this?
Thanks in advance.

If you are stuck using WinForms, your best bet is probably using UserControls. you can actually extend the UserControl class out to be a "page" ie: UserControlPage. This makes the form much simpler in function, but you will need to do some finicky work with handling events /passing data if the controls need to talk to each other.
if you aren't nailed into using Winforms, WPF supports all of this natively, and has wonderful tools for building all the pages you would need, and storing/populating your data, and propagating events.

If you want to have single form with changing content, and you don't want to mess up with panels in one form, then solution is user controls. You will be able to create them dynamically and add to form controls. Also there is no mess, because your form will be very simple - you can have single 'placeholder' control which will be used to dock user control which is currently displayed (e.g. panel control):
private void ShowContent(Control content)
{
placeHolderPanel.Controls.Clear(); // clear current content
placeHolderPanel.Controls.Add(content); // add new
content.Dock = DockStyle.Fill; // fill placeholder area
}
Usage:
private void button1_Click(object sender, EventArgs e)
{
ShowContent(new FooUserControl());
}

You could subclass the Panel class and create as many of those custom panels as needed, then they would be inserted on your Main Form, and managed as you described.
The advantage is that you would be able to individually edit them as a separate user control.
The drawback is that you lose direct event handling of controls on those panels from the main form. You can still define your own events on those panels and delegate the individual control events.
There's always a trade-off somewhere.
Cheers

Force a form to stay on top

I want a form to be shown modal every time it is opend. Since I can not change the way it is created and opend. I wondered if it is possible to make the form stay on top from within the forms class.
One opportunity is the TopMost property. This works in general, but if I display the form while the main thread is waiting for it to close, the form will stay on top even if I change the application(to a browser for example). So no matter where I am, the form is still displayed.
Another issue which I came across is that in some cases it is adopted by the parent form which then might block other windows or popup messages.
I was thinking about a hook to the OnLostFocus event to get it on top again, once the focus is lost, but I'm not sure if that is a good idea ...
Any helpful thoughts about it?
Edit
Due to the comments I will extend my description, Here is the real use-case
We are using the Devexpress's SplashScreenManager which is able to show a certain form as a WaitForm. Since the WaitForm is not intended to be shown modal(see on the Support Center), we are looking for a way to do so.
We can not change the way the form is shown, because this is done through the SplashScreenManager. The WaitForm is shown both from the main thread, as well as from certain backgroundworker.
So this is only about an own form of ourselfs, displaying it within our own application.

Use:
TopLevel = true;
This will do exactly what you want; be topmost as long as the main form is shown and hide if the mainform is hidden by another window.
You can set the owner of your splash form to your main form explicitly without using .Show(owner).
splashForm.Owner=mainForm;
splashManager.Show(splashForm);

We did not want the TopMost property since it works on windows level and covers other windows too (for example the browser).
In the end I hooked up on the focus event of the window to make sure the window is always on top.

MessageBox doesn't show on mdi form after a long calculation

This is a very similar problem to This one, sadly that one was never answered either.
I have a MDI Main forum that hosts several children forms. One of them does a long calculation and throws an exception if an error occurs (all work is done on the same thread). I then try to inform the user of an error with an messagebox, however it doesn't appear (but steals focus from the MDI Main, so the application is completely unresponsive).
The beheviour changes slightly if I call Application.DoEvents() (evil I know, but this is a last resort thing). Then the forms remain completely active and the messagebox only appears after I change active application (Alt+Tab) to something else and then back again.
What can I do to make sure the messagebox will be visible? I have already tried passing both, active child and MDI Main as parameter to the MessageBox.Show method. It doesn't change the behaviour.
To clarify: the messagebox is a part of the child form, however at this point I am willing to show it in any way that doesn't break the application. The messagebox should be modal, but it should be visible so it can be acknowledged by the user.

I had the same issue. When pressed ALT the popup showed.
It turned out to be a LinkedLabel that had the AutoSize property to true. The LinkedLabel was inside a FlowLayoutPanel. When I set the LinkedLabel.Text property to String.Empty. The LinkedLabel constantly tried to resize, which was causing the GUI to be constantly busy.
When I turned off the AutoSize property and the GUI no longer had to recalculate the positions. The GUI was no free. And the popup showed.
There could be other controls that are behaving the same.
See also:
https://connect.microsoft.com/VisualStudio/feedback/details/116884

Is the MessageBox shown in the MainForm or as part of the ChildForms? If the MessageBox is in the child Forms maybe you could pass an event back to the MainForm and open the MessageBox there.

The problem is that messageboxes tend to be modal.
In this instance I think that you'd do far better to use a delegate or an event with a handler in your main MDI code. That way your main application displays the message boxes. You can easily redefined an EventArgsType if you wish to pass whatever information that you require.