There are several similiar questions, but they all seems to be asking for the opposite behavior. I have a data-bound combobox, and I want users to be able to locate values in it by typing, as if it were a textbox. This behavior is easy with IsEditable, but it results in the user being able to select values that are not in the ItemsSource.
When a user does this the Combobox highlights red, but thats it. I want it to actually clear the value out, or select the closest match, whichever is easier. Is this possible without also binding to the text, and putting validation logic in the setter?
No, there is no simple way to solve that problem out of the box.
You'll need to either do as you said, bind to the text, or more correctly (in my opinion at least), make a specialized derived ComboBox/attached behavior where you handle this between PreviewKeyPressed, TextChanged, LostFocus etc.
From personal experience, it can be painful to make custom behaviour like that work perfectly.
I agree that what you'd prefer in a perfect world is the readonly combobox, but with improved "search as you type" where you can actually see what you've typed and edit that on the fly.
Related
I've stuck with one pretty trivial problem (at first look).
Simplified version of my situation looks like this:
I want multiple Background(for example) colors to be applied to SAME Control and to be able to clear only some of them (by condition). WPF does not offer such capability, I can set only one value for each DP.
So, I want to apply Yellow then Green then Red colors successively to Control object and then be able to reset Red so that Control will be with Green background (on the other hand, reseting Green leaves background Red). Looks pretty simple, have you ever created such Decorator for Control? I believe DP internally use such behavior, but there are no public APIs for it.
Please, do not suggest using triggers or any other kinds of conditional DP setting, I really need to set multiple values for single DP and to be able to manage them
Its not a good idea to say "do not suggest" ... Anyway, Well its not possible, and WPF does not do this, what you might meant is the value precendence but this List is fixed, you can't just add another layer in between, for good reasons. The whole system relys on that. Otherwise you could not set one value and use triggers to override it and don't need to take care of resetting the value. Also animations, Style inheritence etc. wouldn't be possible if people start to mess with this list.
So you don't like the trigger idea ... Why? Its exactly for that.
Ok, if you don't like it, how about adding an attached property for Background1, Background2 etc. You also could make Background as an attached property and make it inheritable. You could make an attached behavior, listen to property changes and modify your Background color. You could use a MultiBinding or PriorityBinding.
Well alot of stuff is possible if the obvious solution is not desired :)
I have a following requirement for a very complex UI. (Complex here means there are lot of controls in the form [approximately 100]). I am using MVVM (if my problem requires it to slightly go away from MVVM I am ok with it)
My question is for Editable ComboBox and TextBox. But I would say I like to hear a common algorithm which will fit all controls.
Requirement 1 : The user edits the content and goes to next control, the color of the control/text should become red.
Requirement 2 : When the user comes back to the previously edited control and enters the value which was initially present, the color of the control/text should become back to black.
I know the requirement is tough and I have been breaking my head to design a generic algorithm using which I can store the previous value and call a function to change the color of control.
To just give you all an idea, --> I tried storing 2 properties for every TextBox like Default_Text and Text. But since the number of properties are huge, the memory footprint is very huge. Also maintaining so many properties is very tough.
--> I tried adding a Dictionary to every ViewModel to store what values have got changed. But here the problem I faced was giving unique keys to all the controls in my application, which is not very helpful
--> I had even thought and tried about subclassing controls like TextBox, ComboBox and overriding some methods to suit my requirement, but sadly I failed miserabley when I started adding validations and all.
So here I am stuck with designing a generic WPF property system/algorithm to handle all undo redo functionality, changing styles of controls,etc!!!
It will be really great if you experts can guide me in right direction and also help me in developing such an algorithm/system. A sample illustration will be nice though!!!
I found an answer to the above problem. I used attached behavior for this. More details on this link Function call from XAML from StackOverFlow.
When I databind, I store the initial value of the DataBound variable in the Tag property by using Binding=OneWay. Then I have written a attached behaviour for LostFocus event. Whenever the user enters a control and then goes to other control, it fires LostFocus event and calls my attached behaviour. In this, I check whether the value is equal to the value in Tag. If it is same, I display in black else I display in red.
Attached Behaviour rocks in WPF. I can achieve anything from that cleanly without code cluttering!!!!
Another alternative is to use some "dirty" tracking in your models (or viewmodels) and bind to a properties isdirty (and convert it to a color).
I need a ListBox which will contain several options. I need checkboxes exactly(style), not radio buttons. Is there any way i can allow only 1 checked checkbox at the moment? I'm using MVVM, so i can't just check or uncheck them manually, it's against the rules.
And if i can't make such functionality - is there easy way to style radiobuttons to look like checkboxes?
Aside from a flawed requirement*, the only way to do this is to uncheck all checkboxes, then check the particular indexed checkbox.
Or alternately (cos it does the same thing, but sounds longer), iterate through all the indicated checkboxes and find whichever one is set to true that is not the one you want checked, then set it to false.
flawed requirement: A series of checkboxes indicates to any user that they are allowed to select zero or more items. A series of radiobuttons indicates that they are allowed to select only one. This is something that has been drilled into users since before Windows 3, and that all non-IT will not question. You'll break their mental model, which is worse than looking pretty. Please have management revise this requirement.
HTTH. YMMV.
If you are using MVVM and what to stick to the "rules" then your ViewModel should have a property to which the checkboxes bind. Its the up to code in the ViewModel to ensure that state of this property is correct.
So code in the ViewModel where one property gets set to true may need hunt through a collection to find similar items whose matching property needs to be forced to false. The View then simply reflects the current state of the ViewModel.
Well, in the end, i used this solution
I'm pretty green when it comes to WPF, so forgive me if this is an obvious question.
I'm trying to modify an existing code base that is using the Divelements SandRibbon libraries, but am finding that the GalleryButton control doesn't behave quite how I'd like. What I'd like to do is change the way GalleryButton arranges the image and label, but keep the default 'look' for all triggers such as mouse over etc.
Is it possible to apply a ControlTemplate to some parts of a control but not others? I want to specify that the GalleryButton displays its 'Image' and 'Text' properties differently than the defaults, but not touch anything else.
Unfortunately no -- it's all or nothing. However, one solution I've used before is to simply sublass the control and alter the layout in code behind in OnApplyTemplate.
I have a question regarding a ComboBox in silverlight and it's selected item.
I would like to determine what triggered the SelectionChangedEvent, was it the user selecting a new item in the list or was it programatically set?
While ideally I would like to solve this using the CommandPattern (I am essentially using a modified RelayCommand (http://joshsmithonwpf.wordpress.com/2008/11/17/emulating-icommandsource-in-silverlight-2/). I am open to other suggestions.
I have also played around with the SelectionChangedEventArgs, which has an OriginalSource property, which upon first inspection may appear to help, however it is null (regardless of the manner in which the item was selected.)
Any ideas, other than setting an internal flag? :)
Thanks
Unfortunately this is a tough thing to determine, since the framework works pretty hard to simply bubble up any changes or user events in this situation as that selection changed event.
If you really need to, you could write a simple ComboBoxWrapper that is effectively the flag you're talking about - so you could derive from ComboBox, try overriding or hiding the CLR setter for SelectedItem, and then maintain state that way.
Any particular scenario in use here? There may be another way to approach a solution.