c# - create invisible user control

I need to create a user control in C#.Net, which can be added to the application without being visible - just like the FolderBrowserDialog. It's a new window which I'll be using often so I think this is the right way. The window开发者_JAVA百科 will be opened by envoking the showDialog-Method as known from the other dialog.

Any Idea? Thanks and regards,

Daniel

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Since all these "invisible" controls derive from Component class, you should start by reading the MSDN article on it: http://msdn.microsoft.com/en-us/library/system.componentmodel.component.aspx.

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simply set Visible to false or isn't this what you're asking for ?

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A UserControl is by definition not a Form; I think what you really want is a Component. That said, couldn't you really just create a new Form class that has the functionality you want? Whenever you want to display it, create a new instance and call ShowDialog. Or, if you want to preserve state, add an instance as a class member to your parent form, call its Show method whenever you want to display it, and add an event handler to its FormClosing event to check:

if (e.CloseReason == CloseReason.UserClosing)

and, if so,

e.Cancel = true;
Hide();

(This last part is to prevent errors if the user closes the form and then tries to display again after it's been disposed.)

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I think more information may be needed, but if your crating a custom user control, the control should have a .Visible property. The follow is an example of how a button can be located on the form but hidden from a user.

button.Visible = true;  // shows the button
button.Show(); // Shows the button
button.Visible = false; // hides the button
button.Hide(); // Hides the button

While the button may still be on the form/control, it will not be interactible by the user. You can still perform programmatic control on the button, but essentially it is not a user control while it is 'hidden'. If you want there to be a sort of hidden button that the user can click you will need to do other things to obtain this but It doesn't should like that is what you want.

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This show/hide thought process sounds a lot like pains and confusion leftover from classic VB. The old form methods of show and hide, etc., were confusing and often left me as a developer in a position to not know whether an object existed or if was merely invisible. And checking was only trivial if you used On Error Goto to prevent a null reference. So right off I would advise not to think in terms of visibility unless you are doing something with a web page and need to maintain space and state.

First, create a Windows form and add it to your project, assuming that is the type of project that you are describing. Decorate the form with the proper controls, and where applicable, create properties to allow public access to the control values. Also set the DialogResult property of the buttons that either "OK" or "Cancel" the form. Give it an appropriate border style of either Fixed3D or FixedDialog. Maybe also set the property for where you want the form to appear on startup -- center parent, center screen, Windows default, etc. The event handlers for both "OK" and "Cancel" should invoke this.Close(); to close the window.

From the calling point in the code, here's some hypothetical code to get you going in the right direction. Write something like this in the place where you want to invoke your Dialog.

int intResult = 0;
string strResult = null;


MyDialogForm frm = new MyDialogForm();
frm.Title = "Select an Item";
frm.SomeProperty = 0;
frm.SomeOtherProperty = true;
if (frm.ShowDialog() == DialogResult.OK)
{
intResult = frm.Result;
strResult = frm.StringResult;
}
else if (frm.ShowDialog() == DialogResult.Cancel)
{
// User clicked the cancel button. Nothing to do except maybe display a message.
MessageBox.Show("Canceled Task");
}

...

// Somewhere further on down, but within scope, simply repeat
// what you just did, but without having to reinstantiate the
// form Window. But if you make it that far within the same
// scope, this method might be too busy and may need to be
// factored down.


So in short:

• Scrap show/hide -- its not a good practice.
• Save the form data without using an invisible form to save it; that's the class's job.
• If the UI requires a lot of flipping back and forth between windows, check your design for other alternatives for solving the original problem. Maybe a design pattern such as MVC is for you, depending upon the size and complexity of your application.

Sound good?

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You can put that control in a Panel. Set the panel height = 0 visible = false when you dont want to show the control. And do the vice versa when you want to show it.

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Derive from Control, not UserControl, and in the constructor set Visible = false.

Also create an event handler in the constructor.

VisibleChanged += new EventHandler(SetVisibleFalse);

Create a method named SetVisibleFalse.

private void SetVisibleFalse(object sender, EventArgs e)
{
    if (Visible) Visible = false;
}