Problem:
I cannot add any controls to a groupbox, if the controls were declared in another form.
Background Information:
I have MainForm which inherits from Form. It provides some functionality which I need in all of my forms, and have also added some custom controls/images which I need in all of the other forms.
With my forms, I reposition the controls/images from the MainForm to wherever I need and all is well.
But for some reason, I cannot move these same controls/images into existing GroupBoxes.
When I say can't I mean that VS is not letting me; when I drag the control over the groupbox, my mouse cursor switches to this "error" sign:
If I understand correctly then you have two or more level of inheritance hierarchy with your form, base class have the GroupBox you're trying to modify it in designer via derived form. Am I correct?
In that case VS prevents you to move control to groupbox which is declared in base class?
If yes, There are couple of things to check.
Check whether your groupbox is atleast protected, so that you can access it in derived class.
If yes, While you're dragging the control just right click the mouse(holding left button), then drop it into groupbox. It should work.
If you have troubles yet make the groupbox as protected internal and give a try.
Hope this helps
Related
I have a WinForms application with a GroupBox in it. I have designed a user control which groups together a bunch of textboxes and other controls so that I can apply some custom logic to them. The user control looks like the following:
I want to place this user control within my GroupBox, however doing so ends up affecting the layout of the controls within my user control (see below).
As you can see, my textboxes are all spread out and resized from how I want them to be. If I place this control directly on the main form or in a Panel (not in the GroupBox) the layout is maintained, however the moment I place it in the GroupBox everything gets messed up. Is there a way to fix this problem?
The user control seems to have a different size in the two cases. Make sure it has the same size in the group box as when you place it directly on the form. If you have used a layouting control like a FlowLayoutPanel or a TableLayoutPanel, this might be of importance.
Also be aware that winforms controls inherit properties from their parent if they are not set explicitly. E.g., if you have not set the font property of the user control and its text boxes, those will be taken from the group box.
What ended up working for me was making a separate class MyGroupBox which extends GroupBox. The class is empty, but I converted the GroupBox on my form to this and placed the user control inside, which solved the problem.
Could someone please tell me the differences between using a Form, Panel or a UserControl.
A form is a control and a container for other controls. A form is the base unit of a windows application.
A panel is a control and a container for other controls.
A usercontrol is a user defined control.
See:
Windows Forms
Windows Forms Controls
Windows Forms Overview
In Windows Forms, a form is a visual
surface on which you display
information to the user. You
ordinarily build Windows Forms
applications by adding controls to
forms and developing responses to user
actions, such as mouse clicks or key
presses. A control is a discrete user
interface (UI) element that displays
data or accepts data input.
When a user does something to your
form or one of its controls, the
action generates an event. Your
application reacts to these events by
using code, and processes the events
when they occur. For more information,
see Creating Event Handlers in Windows
Forms.
According to MSDN the Panel class is "Used to group collections of controls", while the User Control "Provides an empty control that can be used to create other controls".
You are right: this doesn't help you a lot to decide whether you should use a Panel or a User Control.
One of the differences is that a Panel is a ScrollableControl, while a UserControl is a ContainerControl (which is also a ScrollableControl). So if you want ContainerControl functionality, consider to use a UserControl.
You'll probably don't know what a ContainerControl does, so what you can't do with a Panel, hence the following might be more useful:
In object oriented programming, and so also in Winforms, whenever you want a class that behaves like another class, but only slightly different, you consider to derive from the other class.
So if you want a button that changes color when pressed, and returns to its original color when pressed again, (like an on-off button), you might consider to derive from class Button, or maybe from class CheckBox-in-the-shape-of-a-button.
By making it a separate class, you can reuse the code in similar situations. Whenever you will only use it once, then usually we won't bother to make it a special class. We will usually not make a special class for "The Select button in my form, which does ... when clicked", but if you will use this button in ten different forms, then it is probably wiser to create a SelectButton class.
Similar, if you have a group of controls, with some behaviour, and you plan to use that in different forms, consider to create a User Control, where you put this behaviour. The nice thing is that the code of this behaviour is hidden inside the control. Users of your UserControl only have to know what it does, not how this is done. You might even want to hide how this is done, so users (= code, not operators) can't access it
A panel is more or less like a GroupBox without a surrounding rectangle: consider to use it instead of a User Control if you will be using it only inside this Form. Similar to how you would us a "Button that does ... when clicked": because you use it only here, you don't derive from it.
I seldom use a Panel. The derived classes: TabPage, SplitterPanel, ... are more likely to be used only in this form.
Whenever I need combinations of several controls, especially if they interact with each other. For instance, if you have a text box and a label that describes what is in the textbox and an OK button that processes the text in the text box. In that case I usually make it a UserControl.
I could have derived from a Panel and add a Label, TextBox and Button, but then users could mess up with my Panel by adding other items, or calling Panel functions that would mess with my functionality.
Come to think of it: using a class derived from a Panel vs using a UserControl is similar to deriving vs aggregation / composition: If you aggregate, you can limit access to functionality, if you derive, users can access all parent functionality.
So if you only want limited functionality: show / no show, maybe size and position, background, but not much more: consider to create a UserControl. If you want the possibility to change the behaviour, consider to use a Panel, especially if you will use it in only one form.
I have a WinForms user control Host with a custom UI Editor.
Through that editor, a child control (Child) can be added to Host.
(The UI Editor creates Child and sets Child.Parent = Host)
Child is handled through a Holder<Child> helper class, which is set as Tag property of e.g. a ListViewItem.
The respective code - some of it, at least - gets added to the form: Holder is created, and set as Tag, which is enough to be created at runtime, too.
However, Child is not visible to the designer - it is displayed, but it can't be selected, nor does it occur in the drop down list with controls for the parent form.
I would like to:
see the Child control in the designer, so that I can modify properties
get notified if the control is removed
Is this possible?
[edit] Thanks all for your input. I've decided to skip the designer - I hoped to throw together something quickly, but apparently it requires more planning than I should allow myself to spend on it right now.
Usethis.Controls.Add(/*Instance of the child*/); on the host class. Then for the notification add event handler for the host's ControlRemoved event (this.ControlRemoved += new ControlEventHandler(Host_ControlRemoved);).
I can't say I fully understand exactly what you are trying to do.
If you are dealing with the problem of how a "child" Control of a UserControl placed on a Form at Design-Time can be made to function as a container onto which you can drag-and-drop other controls from the Toolbox : this CodeProject article by Henry Minute may be helpful : Designing Nested Controls. For example : you have a UserControl with a Panel inside it : an instance of the UserControl is placed on a Form : in the Design-time view of the Form : you want to be able to drag-drop controls onto the Panel in the UserControl and have them become child controls of the Panel : Henry's article will show you how to do that.
This from Microsoft : How to make a UserControl object acts as a control container design-time by using Visual C#
Perhaps might also be useful, although it seems like you already have this step accomplished.
I have a composite control that is includes a groupbox control. The problem is it covers the controls that are placed on top of this composite control. Even though I send the new controls to top, so they should be visible, but they aren't.
When I just use the groupbox, of course it shows through things so you see the included controls, just outlined by the groupbox.
Should I have to do something to get the same effect/behaviour in a composite control?
EDIT: Left side shows the control in the designer, right side shows the control at runtime.
It is possible Quintin is right, and that something is going wrong with the designer support of your control, that is, you've created ControlA, and are extending it to ControlB by adding a button at design time. When you instatiate ControlB, the button is not visible.
Can you verify at runtime, using breakpoints/asserts/etc that:`
ChildButton exists.
ChildButton is a member of CompositeControl.Controls.
ChildButton location is 'in-view' of the CompositeControl.
ChildButton is visible.
If it were me, I'd set a breakpoint in the constructor of the control, and ride into InitializeComponent(), checking that everything is created and added correctly. If ChildButton exists, and has a reference in CompositeControl.Controls and its location is in-view, then I'm at a loss to explain why it's not showing.
If you are meaning that you would like the custom control to behave like a container (like a groupbox normally does) then you need to let the control and the designer know how it should be treated.
Remember to implement IContainerControl and decorate the object with the appropriate designer attribute for designer container support IE:
[Designer("System.Windows.Forms.Design.ParentControlDesigner,System.Design", typeof(System.ComponentModel.Design.IDesigner))]
I tried to create a custom user control in C# that handles other controls that are added to it. The custom control consists of two panels. What I'm trying to achieve is, that if another control is dragged to my user control in design mode (or added programmatically at runtime) I want that control to be placed on one of the panels.
I tried to handle the OnControlAdded event but that didn't do the trick...
Markus wrote : "if another control is dragged to my user control in design mode (or added programmatically at runtime) I want that control to be placed on one of the panels."
I am going to interpret the above as meaning you want the Design-Time dragged control to become a child control of one of the two internal Panels of your UserControl : if that intrepretation is wrong : please disregard what follows :)
Also, just to avoid confusion : you are absolutely correct when you observe that Panels, or other "container" Controls, in an instance of a UserControl placed on a Form at Design-Time, do not "consume" or "swallow" dragged over controls as you might expect : in fact you can't even select them individually : they are added to the UserControl's ControlCollection.
Fortunately for you, in the design-time drag-drop case there is a good solid code example you can study and use on CodeProject by Henry Minute : Designing Nested Controls : that article will show you how to inherit from ParentControlDesigner so that child controls which are containers of a UserControl at design-time can function as containers in the way you are looking for.
In the case of your wanting the consumer of your control at run-time (programmer) ... assuming they don't have source, so they interact with your UserControl as a "black box," able to "see" only Properties, and Methods, available Events, etc., you've made Public ... to control where an added Control is placed : you have a decision to make about how you wish the consumer to access the Panels. You could expose them "directly" as objects, via Public Properties of the UserControl, or you could expose only a Public method for adding controls for each panel.
Why not just drag it into the panel, or give one of the panels a public accessor and do all your programmatic adding to that panel directly?