I am working on a dynamic search view wherein clicking a button should add a new row containing 3 combobox and 2 textboxes.
How should I go about doing this?
If you really want to do mvvm , try to forget "how can I add controls". You don't have to, just think about your viewmodels - WPF create the contols for you :)
In your case lets say we have a SearchViewModel and a SearchEntryViewmodel.
public class SearchEntryViewmodel
{
//Properties for Binding to Combobox and Textbox goes here
}
public class SearchViewModel
{
public ObservableCollection<SearchEntryViewmodel> MySearchItems {get;set;}
public ICommand AddSearchItem {get;}
}
Till now you dont have to think about usercontrols/view. In your SearchView you create an ItemsControl and bind the ItemsSource to MySearchItems.
<ItemsControl ItemsSource="{Binding MySearchItems}"/>
You see now all of your SearchEntryViewmodels in the ItemsControl(just the ToString() atm).
To fit your requirements to show every SearchEntryViewmodel with 3Comboboxes and so on you just have to define a DataTemplate in your Resources
<DataTemplate DataType="{x:Type local:SearchEntryViewmodel}">
<StackPanel Orientation="Horizontal">
<Combobox ItemsSource="{Binding MyPropertyInSearchEntryViewmodel}"/>
<!-- the other controls with bindings -->
</StackPanel>
</DataTemplate>
That's all :) and you never have to think about "how can I add controls dynamically?". You just have to add new SearchEntryViewmodel to your collection.
This approach is called Viewmodel First and I think it's the easiest way to do MVVM.
One option is that you can create TextBoxes and comboboxes in backend by creating a new instanse.
But the better option is that you can create one usercontrol which contains All texboxes and comboboxes which you want to add and in which format you want.
After creating when the button is pressed you can create a instace of this usercontrol and set it in the grid or any other control by using SetValue property of the control.
If you are new to WPF and MVVM this read this blogs to understand this.
https://radhikakhacharia.wordpress.com/2012/06/01/wpf-tutorial-3/
https://radhikakhacharia.wordpress.com/2012/02/13/model-view-viewmodel/
If you are new to both MVVM and WPF, there is a really wonderful video tutorial on how to
architect a C# / WPF / MVVM application by Jason Dollinger which is available here on lab49. All of the sourcecode he developes in this amazing video is available also right here on lab49.
After watching it, you will not have any problems developing your search view for sure.
Related
Just started learning MVVM. I have a tabcontrol where I am adding multiple instances of same views/pages
Dim tb As New UXTabItem
tb.Header = "Childrens"
tb.Name = "tab" & itrt
itrt = itrt + 1
tb.Source = New Uri("/Views/childrens.xaml", UriKind.Relative)
UXTabControl1.Items.Add(tb)
Since each of the same view will handle different data but since the uri is same so all the tabs get populated with same view and changes reflect on each tabs. Which should not be the case. Should I be using a separate viewmodel for each of those? Any example would be much helpful.
One of the primary goals/advantages of MVVM is that you don't create WPF UI objects in code.
You should be populating a collection of view model objects and binding the ItemsSource of the TabControl that you define in XAML to it. You should have a DataTemplate defined for the data type of those objects and put their XAML in there, instead of loading it at runtime.
The TabControl is a little tricky, because it uses two templates: the ItemTemplate is used to define the look of the tab, and the ContentTemplate is used to define the look of the tab items' content. It's pretty common to see this:
<TabControl ItemsSource="{Binding MyItems}">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Text}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<ContentPresenter Content="{Binding}"/>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
which populates the tab with a Text property on the view model, and the tab item's content with whatever template in the resource dictionary matches the view model's type.
I would have an ObservableCollection<TabViewModel> Tabs in my parent ViewModel, and bind the TabControl's ItemSource to that. Each Tab has it's own instance of TabViewModel, so adding a new Tab would mean adding a new TabViewModel to the Tabs collection in the ParentViewModel.
The TabViewModel would contain properties for things like Header or Uri, and these would be bound to the UI at the appropriate spots. Each TabViewModel can be drawn using the same View, but the data inside the object would be different for each tab.
My ParentViewModel would also contain a TabIndex property that defines which tab is selected
This is NOT trivial, IMO, and Rachel and Robert are both right.
Think of this task being one of managing 'work spaces", each represented by a tab control. I like to structure my view models into three related layers
DetailViewModel - the model for a given workspace (represented by a tab control)
MasterViewModel - the model for a collection of detail view models (ObservableCollection{DetailViewModel}). You would use this to bind to a list ion our presentation that shows what items may be selected for editing / display in a tab control. This is where filtering of the list would also be handled, if you allow that.
ShellViewModel - the model that actually has a collection of workspaces (ie, ObservableCollection{Workspace} along with the commands to manage them (ie, EditWorkspaceCommand, AddWorkspaceCommand, DeleteWorkspaceCommand). A workspace is a DetailViewModel that has a CloseCommand.
I found Josh Smith's MVVM article on MSDN useful for grokking this design.
HTH,
Berryl
I've been learning the MVVM pattern with Josh Smith's article and I want to create a classic layout with some links to the right (managed with commands) so when I click one I can show my view to the right into a tab control (inside it there is a ContentControl).
This is simple when I use a DataTemplate with the specific View and ViewModel I want to show on screen like this.
<!-- this section into my MainWindow's resources file -->
<DataTemplate xmlns:vm='clr-namespace:WpfFramework.ViewModels'
xmlns:vw='clr-namespace:WpfFramework.Views'
DataType="{x:Type vm:MySpecificViewModel }" >
<vw:MySpecificView />
</DataTemplate>
But, I want something more generic. I mean that my mainWindow should not know a specific View nor a specific ViewModel. It should only know that it binds to some commands and has a tab control which shows "some view". Every sample including Josh Smith's article seems to have limited universe of views and viewmodels, that's great with a sample.
So, how can I tell my ContentControl that some view (with its corresponding viewModel) is gonna be there without being so specific (without "burning" into the mainView the concrete types)?
best regards
Rodrigo
PD. I have tryed with base a ViewModel and Base View but it doesn't seem to work.
In your main View, bind a ContentControl to a generic ViewModelBase property
<ContentControl Content="{Binding CurrentPage}" />
CurrentPage would be defined in the main ViewModel as a ViewModelBase object, and to switch pages you simply set CurrentPage to whatever you want.
So when you click on something like the HomePageCommand, the main ViewModel would execute CurrentPage = new HomePageViewModel(); providing that HomePageViewModel inherits from ViewModelBase.
I wrote something a little while ago that shows some samples here if you're interested
I'm planning a WPF application which will build dynamic grid with textblocks in the viewmodel and then refresh interface (xaml) with the new grid.
I've done the firts step, but i have problems to refresh the view with the new grid.
Is there any example code of how to bind the grid to the xaml that I can have a look at?? I really can't figure this out!
Thanks
You may be approaching this slightly wrongly, hard to say from the question-
Generally to show a dynamic set of UI elements in MVVM you bind the ItemsSource property of an ItemsControl to an ObservableCollection. The ItemsControl ItemsTemplate property converts the YourViewModel object into a UIElement which can be a TextBlock or whatever style you want.
So as an example:
// model
class Person
{
public string Name {get; private set;}
}
// view model
class MainViewModel
{
public ObservableCollection<Person> People {get; private set;}
}
//view
<UserControl DataContext="{Binding MyMainViewModelObject}">
<ItemsControl ItemsSource="{Binding People}">
<ItemsControl.ItemsTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"/>
</DataTemplate>/
</ItemsControl.ItemsTemplate>
</ItemsControl>
</UserControl>
I havent tested that code, it is just to illustrate. There are other ways of dissecting the problem into MVVM, it all depends on the situation. You would have to give more details for us to help you out with that. Rarely in WPF is there a need to use code to create or add UI elements to other UIElements etc.
A point to note more along the exact lines of the question however is that an ItemsControl can either bind to a bunch of regular objects and use it's template to create UIElements from them, OR it can bind to a list of UIElements, in which case the template is not applied (sounds like this is the situation you have).
I have a lot of check boxes in my WPF form. I want to get the selected checkbox value alone. In Winforms we can use foreach(checkbox ck in controls), but I cannot use like that in WPF Forms. How can i get the selected checkbox in WPF?
First of all, WPF is not just another replacement for WinForms, So the tricks in Winforms might be little different than WPF. WPF is all about DataBinding, so read about MVVM pattern which will really help you in WPF development.
Now coming to the way to go with MVVM approach fort this, Imagine your ViewModel class contains a collection of bool. Now the DataTemplate has CheckBox.IsChecked property bind to the boolean, So when you change the checkbox the collection will hold the changed booleans appropriately.
public List<bool> MyBoolCollection{get; set;}
<ItemsControl ItemsSource="{Binding MyBoolCollection}" ...>
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox IsChecked="{Binding}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
Can you data bind the IsChecked property for each CheckBox? Bind it to a member variable of the container class. At least this way you can iterate over the member variables to determine if any are checked.
Can anyone point me to a good resource (or throw me a clue) to show me how to do DataBinding to controls (ComboBox, ListBox, etc.) in WPF? I'm at a bit of a loss when all my WinForms niceities are taken away from me, and I'm not all that bright to start with...
The best resource I've found for WPF data binding is Bea Costa's blog. Start from the first post and read forward. It's awesome.
I find the tutorial videos at Windows Client .Net equally awesome. Dot Net Rocks TV has also covered it some time ago.
in code behind -- set the DataContext of your list box equal to the collection you're binding to.
private void OnInit(object sender, EventArgs e)
{
//myDataSet is some IEnumerable
// myListBox is a ListBox control.
// Set the DataContext of the ListBox to myDataSet
myListBox.DataContext = myDataSet;
}
In XAML, Listbox can declare which properties it binds to using the "Binding" syntax.
<ListBox Name="myListBox" Height="200"
ItemsSource="{Binding Path=BookTable}"
ItemTemplate ="{StaticResource BookItemTemplate}"/>
And some more links, just in case the above didn't suffice:
Windows Presentation Foundation - Data Binding How-to Topics
- Approx 30 'How To' articles from MSDN.
"The topics in this section describe how to use data binding to bind elements to data from a variety of data sources in the form of common language runtime (CLR) objects and XML. "
Moving Toward WPF Data Binding One Step at a Time
- By WPF guru Josh Smith
"This article explains the absolute basics of WPF data binding. It shows four different ways how to perform the same simple task. Each iteration moves closer to the most compact, XAML-only implementation possible. This article is for people with no experience in WPF data binding."
Here's another good resource from MSDN: Data Binding Overview.
There are three things you need to do:
Bind the ItemsSource of the ComboBox to the list of options.
Bind the SelectedItem to the property that holds the selection.
Set the ComboBox.ItemTemplate to a DataTemplate for a ComboBoxItem.
So, for example, if your data context object is a person having email addresses, and you want to choose their primary, you might have classes with these signatures:
public class EmailAddress
{
public string AddressAsString { get; set; }
}
public class Person
{
public IEnumerable<EmailAddress> EmailAddresses { get; }
public EmailAddress MainEmailAddress { get; set; }
}
Then you could create the combo box like this:
<ComboBox ItemsSource="{Binding EmailAddresses}" SelectedItem="{Binding MainEmailAddress}">
<ComboBox.ItemTemplate>
<DataTemplate>
<ComboBoxItem Content="{Binding AddressAsString}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
Now you need to implement INotifyPropertyChanged in both Person and EmailAddress. For the EmailAddresses collection, you could back it with an ObjservableCollection.
Or as an alternative you can use Update Controls .NET. This is an open source project that replaces data binding and does not require INotifyPropertyChanged. You can use whatever collection makes sense to back the EmailAddresses property. The XAML works the same as above, except that you import the UpdateControls.XAML namespace and replace {Binding ...} with {u:Update ...}.