I need to build a custom items control in WPF, where the user can drag/drop the items. Normally I would just maintain a list of view models and use a data template to define how the items should be displayed (in this case, a button). But I am concerned that this will make the drag/drop difficult as the ItemsSource objects will be view model objects , not the actual button.
My other potential approach is when an object is added to the ItemsSource, create a button in c# and add it manually, that way I can access the button directly to do drag/drop.
What would your advice be?
I have solved my issue. I found a way to get the control being render from the data template
I need some kind of control to wrap my UI (which generates using binding). Currently I use ListBox but not sure if it's lightest or best choice. I just need placeholder that I can bind to and insert my controls.
You're probably looking for the ItemsControl
You can use any control that takes a list of entities as it's data source.
This could be DataGrid, ListBox (as you are already using) or anything that inherits from ItemsControl - this includes things like the TabControl as well.
This feels like a stupid question, but is there a simple control for WPF that just displays a collection of items? I am currently using a ListBox to display a collection of usercontrols, but the selection element is not needed and the highlighting is actually a distraction. I could disable the highlighting, but this seems like extra work if a simpler control exists. I don't need to track the selected item.
Basically, I want a stackpanel that I can just define an itemssource of viewmodels for. Does such a thing exist?
You can use an ItemsControl - it's pretty much exactly what you are looking for
I have an app with MVVM which works fine. Now I want to replace one of my controls with a dynamic control. By dynamic I mean that I have no idea what control this is, only that it is a GUI control. It could be something as simple as a image, or a custom third party user control that will be created by someone else after this app is done.
Can someone shed some light on how this can be achieved in MVVM? I've done it before a long time ago using ListBox or similar (iirc) to generate GUI elements (don't remember details). But I'd like to learn the theory behind it this time.
Edit:
Lets say the View contains a list of instances of for example System.Windows.UIElement. I want to display all of these UI controls on a surface (for instance in a stacked control).
You could create a View that exposes a Content property as a placeholder (so a ContentControl might be all that is needed) The content property could then be set to the dynamic control.
You would have to add a little reflection to dynamically load the assembly and instantiate the required control.
The dynamically loaded control would have to access the data by using the DataContext property. If the dynamic control is MVVM too it might have its own ViewModel so you would have to find a way to load that too (reflexction again?) and point the DataContext of the control to the loaded ViewModel.
Does this make sense, is this what you are looking for?
I currently need to create a visual representation of a ferry system that displays the actual ferries their position on the sea and the state of their cargo. The ferries contain trucks and the trucks contain cars. I need to display the actual trucks and their xy postion on the deck. When the ferries are loaded the postions of the trucks are updated frequently so the look animated. Also I need to display the actual cars on the trucks. Trucks, cars and ferries have some states that need to be displayed too. So I have a hierarchical structure of data that I need to visualize in a rather realistic manner.
What would be a good way to implement this kind of stuff in WPF? Should I use MVVM with one TreeView control and create a HierarchicalDataTemplates for sea, ferry, truck and car and a ControlTemplate for the TreeView? Or should I better use UserControls and compose and update them in code instead of databinding to observable collections of the ViewModel. Do you have any experience with this? How would you do this? Could you sketch out class/control setup?
I'd recommend making a "lookless" control as opposed to making user controls. Generally I use user controls as glue/container for my lookless controls. An example of a lookless control is the Button class. It contains a default style and in Blend, you can modify the style all you like. It also supports the visual state manager so you can change how the presentation looks when states change. You can think of the codebehind of a lookless control as a mini ViewModel. Here it is ok to mix some presentation stuff and your domain classes.
If you follow this same design, you could create a Ferry lookless control. This control would have a set of it's own dependency properties (possibly listening to the OnChange of the DP).
Your Ferry control may have an ObservableCollection DP called "Trucks".
Then in your Themes\generic.xaml, create a default style for your Ferry control. Your default style may have an ItemsControl with an ItemsSource={TemplateBinding Trucks}. The ItemsControl panel template, could be your own custom panel for arranging the Trucks, or maybe you use a Canvas. For the ItemsControl items template, you would have something like this:
<DataTemplate>
<mynamespace:TruckControl/>
</DataTemplate>
You Truck control, would also be a lookless control with it's own default style, and it's data context will already be set, so you can directly do the {Binding Path=xyz}. Your Truck control could also set it's Canvas.Left/Top (if you chose to use a canvas in the pervious items control..or maybe it doesn't set its position at all if you made a custom panel for it) or a render transform as to put it at the correct X,Y. You could also use the items control in the truck's template to render out the cars in the same fashion you rendered out the trucks in the ferry control. Also its possible to create states for the VisualStateManager as to make it fully Blend supportable. So if a truck goes into a "problem state" you could easily style that state in blend to make it blink red, for instance.
I know it sounds like a lot to digest, but in the end having stylable controls all supporting an MVVM model will make your life 1000000x easier.
I'd suggest studying Microsoft's silverlight toolkit to get a good idea how to do lookless controls and such. Try looking at a simple control, like the DatePicker ( http://silverlight.codeplex.com/SourceControl/changeset/view/25992# ) One caveat is ignore DatePicker.xaml file (it's just a mirror of what gets put in generic.xaml and nothing bad would happen if you just deleted it).
The things you should pay close attention to are:
1.) The attributes on the class. These help Blend know how to deal with your control.
2.) The OnApplyTemplate override. This is where you can pull out specific elements from your template. These are known as "parts" and you will see the parts tab in Blend. The attributes in #1 can define what "parts" are in the template and what type they are expected to be.
3.) The DefaultStyleKey = typeof(...) in the constructor. This tells Silverlight what default template to use in the generic.xaml
4.) Look at Themes\generic.xaml. This is a special hardcoded file location that stores all your default templates. Search for the DatePicker style and you will get the idea :)
Good luck!
I just wanted to let you know, how I actually implemented it. It turned out that it was not necessary at all, to write custom controls or UserControls for this. All I did, was writing datatemplates for the car, ship, ferry, truck etc ViewModels. For example the datatemplate for the FerryViewModel contained an ItemsControl with a ItemsPanel of type Canvas (to be able to position the trucks) and an ItemTemplate that was a DataTemplate for TruckViewModel. A very simple and fast approach.
I'd suggest having one user control handle all the drawing. Otherwise you can get lost the the hierarchy of objects. Also it makes it easier if another item was added, say people in cars, trucks and ferries.
If your model is hierarchical then you can just pass in the top level into the control, and let the control sort itself out.
MVVM works well for existing controls, but existing WPF controls only work if there's a control that's close to what you need, and with a few tweaks would work. I can't think of a standard control in WPF that's close to what you need, so it's time to write a new control.
WPF works really really well with view models. If you can keep code behind away until specifically needed then you can separate ui from data so much more easily. It will allow your ui's to be some much more upgradeable if the data model doesn't change between different display.