I have a listview and would like to update the text of one of the columns for a specific listviewitem (row).
How would I go about doing this?
Hard to say without any context because there are so many ways you could populate your list!
The generic answer is you bind your list to a collection view which itself binds its source to your viewmodel (or you bind directly to your viewmodel if you don't need CollectionView features).
When you want to modify your list, you make sure you raise a modification notification on your property, and XAML binding will take care of updating everything.
It is really basic stuff on dependency property and binding, you should read more about this topic. MVVM-light is a very light framework that allows you to take care of all kinds of binding-related issues with a very clean and neat flavor. You will also find some very good self-explanatory webcasts from the author of the website about all those topics.
Related
I'm trying to make something like a quiz application where 3 questions will be brought up on screen at a time, allowing the user the check a radio button containing "Yes" or "No", and have an answer come up appropriately to his response. The questions will continually come from a database I'm using.
After a few attempts I've figured that using x:Name property is not a great solution, since it doesn't allow me to use a loop in order to change the questions and answers. Is there any other way to make a grid with the same types of objects in each cell, being able to access each object inside each cell of the grid in the code-behind?
Here is list of steps you need to implement,
Need to create QuestionModel, contains question properties, make sure your model inherits INotifyPropertyChanged.
Need to create ViewModel, which contains data objects, public/dependency properties
Need to bind/set data objects/properties on viewmodel constructor
Need to set your ViewModel as a DataContext of your View(.xaml) (You can create this on zammel directly and codebehind as well
Need to bind your UI objects like Question/answers/yes-no with viewmodel properties accordingly
WPF/Silverlight has their own fundamentals like Data Binding, Resources, Compiler, Dependency Properties. Above steps comprises MVVM design pattern. During each steps, please google for specific stuff.
I am using an Infragistics XamDataChart and want to bind a collection in my view model to the chart's Series property, since I don't know in advance how many line charts I will need to display.
From what I can gather from old posts in the Infragistics support forums, the Series property is read only and thus doesn't support binding directly. A solution is offered here but it seems like overkill for such a simple goal (maybe to me it just seems simple).
Has anyone here done any work with the Infragistics xamDataChart and MVVM? The ultimate goal is to be able to have a collection in my view model that contains a variable number of 'series' that I can just bind to the chart. Now I can probably do this if I just write some code behind for my xaml, access the DataContext (viewModel) and listen to the collection property, directly adding/removing series to the chart as necessary, but I was looking for a more MVVM way.
Thanks.
Since the Series collection of the XamDataChart is read-only, in order to be able to generate the Series dynamically,based on you VeiwModel, you should use helper class, similar to the approach that Graham Murray has suggested in the thead that you have referred. I have created a sample applicaiton, that show how you can create similar appraoch for binding the series of the XamDataChart to collection of your ViewModel. You can download the sample from here:
http://users.infragistics.com/Samples/SeriesBinder.zip
Sincerely,
Krasimir
How can I find and access to Elements which are bind to an object in XAML ?
Edit : Let's say I have a EmployeeViewModel which is assigned to EmployeeView's DataContext and a EmployeeModel inside my EmployeeViewModel, I want to know which properties of my model bounded to View's Framework Elements (Controls) also I want to have an access to each control bounded to my model properties.
UPDATE: In light of the question being clarified by SaberAmani in that he is trying to add validation to his models and show a validation summary..see the links below.
http://msdn.microsoft.com/en-us/magazine/ff714593.aspx
http://codeblitz.wordpress.com/2009/05/12/wpf-validation-summary-control/
http://wpfvalidation.codeplex.com/
http://f10andf11.blogspot.co.uk/2012/02/wpf-validation-summary-control.html
For reference for people that want to discover Bindings:
You don't mention if your XAML is in WPF, Silverlight, Metro or Phone7 (thus you may be more restricted in what you can do).
There seem to be a few possible ways to do what you want:
Reflection
MarkupObject / MarkupWriter
TypeDescriptor+DependencyPropertyDescriptor
Custom Binding Markup Extension
Take a look at this link.
http://blog.spencen.com/2008/05/02/how-to-get-a-list-of-bindings-in-wpf.aspx
He uses reflection and suggests this is the classical way to do it...but also mentions MarkupWriter as another possibility. NOTE: the reflection method doesn't discover Attached Properties which may have bindings.
Here are some links that use MarkupWriter...this would allow you to discover the attached properties.
http://www.codeproject.com/Articles/21139/An-XAML-Serializer-Preserving-Bindings
http://blogs.msdn.com/b/marlat/archive/2009/05/24/getbindingexpression-a-good-way-to-iterate-over-all-dependency-properties-in-visual-tree-in-silverlight-3.aspx
Related links:
Retrieve all Data Bindings from WPF Window
Getting list of all dependency/attached properties of an Object
http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/580234cb-e870-4af1-9a91-3e3ba118c89c
you could use reflection to loop through properties and use FrameworkElement.GetBindingExpression on each property to build, for a given Framework element, all its bindings.
http://msdn.microsoft.com/en-us/library/system.windows.frameworkelement.getbindingexpression
I am required to use the mvvm pattern. I know that the viewmodel should not care about the view from what I been reading. As a result I don't know how to solve this problem:
I have a dll that basically turns a textbox and listview into an autocomplete control:
SomeDll.InitAutocomplete<string>(TextBox1, ListView1, SomeObservableCollection);
anyways I don't know how to call that method from the viewmodel using the mvvm patter. if I reference the controls in the view I will be braking the rules.
I am new to MVVM pattern and my company requires me to follow it. what will be the most appropriate way of solving this problem?
I know I will be able to solve it by passing the entire view to the viewmodel as a constructor parameter but that will totaly break the mvvm pattern just because I need to reference two controls in the view.
What you're doing here is a pure view concern, so I'd recommend doing it in the view (i.e. the code-behind). The view knows about the VM and its observable collection, so why not let the code behind make this call?
(I'd also recommend seeing if you can get a non-code/XAML API for "SomeDll", but I have no idea how much control you might have over that)
There are two things that I'd point out here -
First, this is effectively all View-layer code. As such, using code behind isn't necessarily a violation of MVVM - you're not bridging that View->ViewModel layer by including some code in the code behind, if necessary.
That being said, this is often handled more elegantly in one of two ways -
You could wrap this functionality into a new control - effectively an AutoCompleteTextBox control. This would allow you to include the "textbox" and "listview" visual elements into the control template, and bind to the completion items within Xaml.
You could turn this into an attached property (or Blend behavior), which would allow you to "attach" it to a text box, and add that functionality (all within xaml). The items collection would then become a binding on the attached property (or behavior).
I'm a bit confused as to what a viewmodel's role is beyond databinding. I have a menu built in silverlight. The menu has x number of menu items which is determined at runtime. One of the features I would like to add to this is that each menuitem has a different text colour when hovered over.
Is it the role of the view to have a colour selector method or should the view handle this in it's code behind?
Normally I would keep the coloring/styling in XAML if possible - My view of the ViewModel is that it is responsible for providing all the data (ie. not graphical stuff) from the Model in a manner the View can consume.
If it was complex logic that determined the color and it was to be reused - I might be tempted to put it in the ViewModel tho.
The view model is used by the data binding process as a "safe" way to allow you to sort/filter/group the records as seen by a specific control without (necessarily) making changes to the actual bound data set (that is, unless/until you tell it to). (FMI read Bea's article here.)
I agree with Goblin here, in that the presentation aspects like color might be best kept separate in the XAML, for example in the DataTemplate used by that control.