I've written a custom tab control (FooTabControl) which hosts specific tab page controls (FooTabPage instances). The FooTabPages know to place themselves into a dedicated area within the FooTabControl.
Now I wish to have the FooTabControl also host a System.Windows.Forms.Panel child control (in another dedicated area of the FooTabControl). I want the user to be able to place his controls into this Panel, but disallow him from removing the Panel control itself (while still being able to add and remove FooTabPages as he sees fit).
What would be the proper way to implement this?
You need to override CreateControlsInstance (in the custom control) and return you own implementation of ControlCollection.
In your implementation your will override Remove to disallow removing the Panel.
Related
I recently refactored the code of a user control in my WinForms project, and changed it from a user control with text boxes, combo and buttons that were just placed all over it, to a user control that now contains a TableLayoutPanel, which holds all the controls in a better order.
My problem is that in many places the code address the controls nested in the user control directly via the Controls dictionary - for example: MyUserControl.Controls["NameOfTextBox"].Visible = false;
Now, after I nested the text boxes and buttons in a TableLayoutPanel, I can't do such addressing anymore, and now I should write MyUserControl.Controls[0].Controls["NameOfTextBox"].Visible = false;, because otherwise I get an exception.
My question is whether I should change all my code in every place that addresses the contents of the user control, or can you offer me some workaround to implement on the user control itself, so when I'll try address the controls directly, it will forward it to the contents of the TableLayoutPanel.
Any Ideas?
My problem is that in many places the code address the controls nested in the user control directly...
That's probably the core issue. Try creating properties for you UserControl instead:
public bool NameBoxVisible {
get { return NameOfTextBox.Visible; }
set { NameOfTextBox.Visible = value; }
}
Then you can reference the controls directly in your UserControl but provide a separation of concern to the consumers of your control.
I have a custom list control derived from Control class.
I need to make it accessible to people with disabilities through MSAA (Microsoft Active Accessibility).
So far I understand that I need to create class that inherits from ControlAccessibleObject and then return its instance in Control.CreateAccessibilityInstance method override.
The problem is that I have implemented this and it seems not work with Windows Narrator tool.
For example, when I click on an item in standard ListView, the Narrator speaks out the selected item text.
But when I click on item in my control, nothing happens (although the item text is requested in my ControlAccessibleObject implementation)
I thought I need to implement IAccessible as well, but I looked on .NET refrence source code and the ListView does not implement this interface. I thought maybe this is implemented in the wrapped Win32 control, so I took a look on similar control - DataGridView - but this does not implement IAccessible as well.
DataGridView have accessibility support, but although I copied all the important code of DataGridViewAccessibleObject, it still does not work in my control.
Do anyone have more experience with custom control accessibility in WinForms?
Okay, I found it: The Control.AccessibilityNotifyClients method does the magic. One have to override this method in a derived control.
However, to make screen readers speak the text, I had to call:
AccessibilityNotifyClients(AccessibleEvents.Focus, index);
AccessibilityNotifyClients(AccessibleEvents.Selection, index);
Here the index is an index of newly selected item.
I found this code in the .NET reference source of CheckedListBox. When I used Focus or Selection event solely, the screen reader have not reacted. The spoken text also depend on the AccessibleObject state that corresponds to a newly selected item.
I am working on a PRISM / CAL solution, but the problem may be WPF specific:
If I create one instance of an control (e.g. TextBlock) and add it as child to a StackPanel, there is no way to add it as "child" to another StackPanel (parent already set error). I kind of understand the reason (it also occurs when using the RegionManager).
But what is the suggested way if a visual control is very complex and should be created only one time and used in two places? I agree that is does not really make sense to show an identical control 2 times on the screen, but there might be cases where it is useful (e.g. an "Close All" Button).
I know that in the button case, I should just create two buttons both databound to one ICommand. But does this rule also apply with much more complex controls (always create new instances)...
I stumbled on this problem when creating a layout switcher, which creates the button list and the stack panel for each GUI seperately, but uses a static ObservableCollection of buttons as source (which causes strange bugs)..
Any ideas on this topic?
Chris
This is normally handled by templates. That is, you abstract out the data into a particular type, and associate a template with that type. Then you place the instance of that data any number of times into your visual tree and have WPF render it with the template.
In short, don't add a TextBlock to your StackPanel. Instead, add an instance of your data type (eg. Customer) and associate a DataTemplate with the Customer type. There is no way to parent the same UIElement in multiple places.
You can add your control (or collection of controls) as a resource and refer to them via binding in your controls. This will implicitly create a copy (they will be Freezable and WPF will copy them).
Generally you should be using DataTemplates as Kent suggests, but if you have a special case, this will likely work.
How would you render a tag cloud within a .NET 2.0+ WinForm application?
One solution that I am thinking of would be using the WebBrowser control and generating to some ad-hoc HTML, but that seems to be a pretty heavy solution.
Am I missing something more simple?
How about creating a user control that implements the Flow layout control? You could have a method for "Add(string tagName)" that would create a link label on the fly and add it to the Flow Layout control. The Flow Layout works just like the web, in that controls added to it are put in the order of creation.
Then you only have to add some logic to resize the Link Label based on hit count for that tag.
Well, you'll want a control with these major features:
Automatic layout of variable sized string snippets
Automatic mouse hit testing
Those are a bit hard to come by in WF controls. A RichTextBox with ReadOnly = true gives you the automatic layout, but not the hit testing. A ListBox with DrawItem can give you variable sized strings and hit testing, but not a natural layout.
I think I would use RTB and make hit testing work with the MouseDown event and GetCharIndexFromPosition(), reading back the tag at the clicked location. You'll need a bit of logic to find the starting and ending white space around the word.
I have a windows forms application with controls like textbox, combobox, datagridview etc.
These controls allow a user to use the clipboad, i.e. cut/copy and paste text. It is also possible to delete text (which is not related to the clipboard).
My application has a menubar with an Edit item containing Cut/Copy/Paste/Delete items, and a toolbar with these items as well. How can I enable/disable these items properly depending in the state of the control having the focus?
I am looking for a generic way, i.e. I look for an implementation I do once, and can reuse for the future independent of the controls my application will use.
There is no generic interface or set of methods for getting cut/copy/paste information from a windows forms control.
I suggest your best approach would be to create a wrapper class for each type of control. Then when you want to update the menu state you get the current control with focus and create the appropriate wrapper for it. Then you ask that wrapper for the state information you need. That way you only need to create a wrapper implementation for each type of control you use. Bit of a pain to start with but other time you only need to add the new controls you come across.
Clipboard information is much easier as you can ask the Clipboard singleton if it has data inside and what type it is. Then again you still need to ask the target control if it can accept that type of information so there is still extra work needs doing.
Create an array for each enable/disable group. Add the controls to the array (of course it has to be of the correct type such as Object or Any, etc. depends on the programming language you are using).
Then to enable, disable just loop through the array and invoke the enable/disable method or function for each control. Again, depending on the language you may need to cast back.