I have a basic project in WPF.
All it does it retrieve / update products.
As shown in the image below, the user enters an ID, the data is then displayed according to it, and the user is able to change the data and click 'Save Product' to save it to the database.
The GetProduct(int id) function retrieves a product by the ID provided.
The SaveProduct() function saves the changed fields.
Also, there are two DataTemplates:
1) For the ProductModel - includes 3 textboxes: ProductId, ProductName, UnitPrice.
2) For the ProductViewModel - includes the save/get buttons + a textbox for the user to enter the id of the desired product.
What I'm trying to do is get the changed data when a user clicks the 'Save Product' button.
The most ideal way in my opinion, is to use Binding.
Each textbox is already binded, but I have no idea how to get the binded data.
Here is an example of a binded textbox in the FIRST DataType (ProductModel):
<TextBox Grid.Row="0" Grid.Column="1" Text="{Binding ProductId}" Margin="5" Width="150" />
There is one for each of the following properties: ProductId, ProductName and UnitPrice.
IMPORTANT!: The Get/SaveProduct() functions are in the ProductViewModel class, while the actual product class is - you guessed it - ProductModel. The ProductViewModel class holds a variable that contains the current product displayed.
This is the button that's used to save the info - it is written in the SECOND DataType (ProductViewModel):
<Button Content="Save Product" DockPanel.Dock="Right" Margin="10,2" VerticalAlignment="Center" Command="{Binding Path=SaveProductCommand}" Width="100" />
The SaveProductCommand command simply fires the SaveProduct() function.
I have a few questions regarding this whole subject:
What does it mean when a binding is used like this : {Binding ProductId} ?
The default binding mode for textboxes is TwoWay as far as I remember. But in this case, ProductId/Name + UnitPrice are not dependency properties, therefore is it right that the binded values do not update/sent back when the text in the textboxes is changed? (Since there isn't an event attached to it...)
A data context was never configured in my project, but all of the "binding tags" in my XAML pages don't seem to have a defined source. Could it be that the source is actually the DataType in the DataTemplate that includes the binded objects?
The SECOND DataTemplate (the ProductViewModel one) has this ContentControl tag: <ContentControl Margin="10" Content="{Binding Path=CurrentProduct}" />.
What is it's purpose?
If a TwoWay binding were/does occur, how do I get the values from within the SaveProduct() function? Do I just refer to, say CurrentProduct.ProductName to get the changed name?
Much thanks to everyone who takes their time to answer - I appreciate it so much!
What does it mean when a binding is used like this : {Binding
ProductId} ?
The specific control property you have this binding set on is going to look for the ProductId property on the object set as the DataContext and set the propertys value in the control accordingly.
The default binding mode for textboxes is TwoWay as far as I remember.
But in this case, ProductId/Name + UnitPrice are not dependency
properties, therefore is it right that the binded values do not
update/sent back when the text in the textboxes is changed? (Since
there isn't an event attached to it...)
You do not need to make the properties within your object a DependencyProperty for TwoWay binding to occur.
A data context was never configured in my project, but all of the
"binding tags" in my XAML pages don't seem to have a defined source.
Could it be that the source is actually the DataType in the
DataTemplate that includes the binded objects?
The bindings being set within your XAML will use the object stored within the DataContext, thus if you do not explicitly set the DataContext of the view, it will be null. You should note however that the DataContext is inherited from its parent. If you are in fact setting the content by using say, CurrentProduct, then all the properties will be available to bind to per your Product type.
The SECOND DataTemplate (the ProductViewModel one) has this
ContentControl tag:
<ContentControl Margin="10" Content="{Binding Path=CurrentProduct}" />
What is it's purpose?
It is acting as the container of your CurrentProduct, which can contain one and only one item.
If a TwoWay binding were/does occur, how do I get the values from
within the SaveProduct() function? Do I just refer to, say
CurrentProduct.ProductName to get the changed name?
Without seeing the entire application, my guess is that the ContentControl is being set to the CurrentProduct and your TextBox, etc.. are all bound to the respective properties, such as CurrentProduct.ProductId, etc... The product which you want to save is in fact the CurrentProduct. When you call save within your ViewModel, you simply access the CurrentProduct and persist it as needed, where CurrentProduct.PropertyName will contain the changes which were propagated from the UI.
Related
I've got a simple WPF ComboBox, displaying Orders/Positions on the Financial Markets.
<ComboBox Name="TradeDropDown"
HorizontalAlignment="Stretch"
VerticalAlignment="Top"
ItemsSource="{Binding Path=ActiveOrders}"
DisplayMemberPath="OrderLabel"
SelectedItem="{Binding Path=SelectedOrder, Mode=TwoWay}" IsSynchronizedWithCurrentItem="True" />
I need to see at a glance how many items are in the list. I've added a TextBlock above with summary information.
I don't like it, and would prefer to have the items in the dropdown listed like:
(1/2) Working Short 425K
(2/2) Filled Long 979K
etc - and have the 1/2 numbers correctly update as items are added and removed from the list.
The Items are stored in a BindingList.
Is there an easy way to do this?
Is there an easy way to do this?
Add another property to the class where the OrderLabel property is defined that returns a string like "(1/2) Working Short 425K" and set the DisplayMemberPath property of the ComboBox to the name of this property.
Make sure that the class implements the INotifyPropertyChanged interface.
You then set the new property to a new value and raise the PropertyChanged event whenever you want to update the label in the ComboBox.
I am quite new to WPF development, and currently I am trying to use the MVVM on my application development. I have read a lot about MVVM navigation and switching views, but I can't find a solution for my current situation. Let's explain what it is:
First of all, I have my main View element, a Dockpanel, with some fixed areas, and a main "dynamic" area where the content should change, depending on actions:
<DockPanel>
<Label Content="Top Fixed element"/>
<StackPanel Orientation="Vertical" Height="auto" Width="150" DockPanel.Dock="Left">
<Label Content="SomeOptions"/>
<!-- some more elements -->
</StackPanel>
<Label DockPanel.Dock="Bottom" Content="Foot"/>
<ContentControl Content="{Binding CurrentMainViewElementViewModel}"/>
</DockPanel>
I have defined some DataTemplates that I would like to load in this ContentControl, here there is one of the Data Templates as example:
<Window.Resources>
<DataTemplate DataType="{x:Type ViewModel:FileLoaderVM}">
<View:FileLoaderView/>
</DataTemplate>
</Window.Resources>
This FileLoader (View and View Model are implemented, using the RelayCommand and the INotifyPropertyChanged) opens a dialog box after clicking a button, where after selecting a file it is opened and parsed, and show all the found elements inside a ListView with multiple selection(in this case, persons with their data).
What I want to do now is to load another user control in this ContentControl, when I click a button. This button is defined in my view model like this:
public ICommand LoadPersons
{
get { return new RelayCommand(param => this.loadSelectedPersons(), param => (SelectedPersons!=null && SelectedPersons.Any()));}
}
My question comes at this point, how can I modify the content of the ContentControl, loading another User Control instead of the current one directly from my view model (in this "this.loadSelectedPersons()")?
If this is not possible, how should I approach to solve this problem?
Next to this action, I want to show all the previously selected elements and manipulate in different possible ways (inserting in a DB, saving in another file and so on), and I have already for that the appropriate User Control, that I would like to show in my main view element in the ContentControl section, keeping the other elements as they are originally.
lets see if i get you right.
you have a mainviewmodel with a property (CurrentMainViewElementViewModel) bound to the ContentControl. your MainViewmodel set the FileLoaderVM to this Property. now you wanna show a "new/other" Viewmodel when a File is seleted in your FileLoaderVM?
why dont you simply expose a event from your FileLoaderVM and subscribe to this event in your MainViewModel? if you do so your MainViewModel can then set the "new/other" Viewmodel to the ContentControl
To change content of ContentControl you do not load another user control, but change value of CurrentMainViewElementViewModel (to which ContentControl.Content is bound) to a new ViewModel, which will load another UserControl (defined in DataTemplate same way as FileLoaderVM is).
This looks like a job for main ViewModel (where CurrentMainViewElementViewModel is located).
Easiest solution is to provide a method in that ViewModel
public Switch()
{
CurrentMainViewElementViewModel = SomeViewModel;
}
and call this method from FileLoaderVM.
I have defined a UserControl for DateTime picking in Windows 8 store apps. The control consists of 3 checkboxes and hast a property to channel out the selected date time.
When I include this control into another UserControl and name it, I am not able to access it from C# code.
//...Page content....
<TextBlock Text="Erledigen bis:" FontSize="16"/>
<local:DateTimePicker Name="dtp_dueUntil" />
<TextBlock Text="Wichtigkeit" FontSize="16"/>
//...Page content....
*dtp_dueUntil* is not known in my code behind file.
Am I doing something awefull wrong, or just missing a point here?
You should not access controls like that, unless you have no other choice. In your case, iF you what to expose selected DateTime in your first user control, then simply declare a Dependency Property which will hold and update this value (via DataBinding or event).
I am currently customizing a ListBox. With that I mean adding an image-element, second line-element etc. to one listItem.
The itemSource is a List in C#, therefore I have no preview of the items in Expression Blend/VS. And that's the pain.
Because I have always to edit the XAML and then deploy to check. And this goes on and on until the last pixel is correct.
Isn't there a way, of editing a ListBox with custom items (with a dynamic itemSource) live in Blend/VS?
That would really fasten up my developing.
If you want to see how your controls look like in design time, you must use SampleData. There are several ways to do it, it depends on your framework.
Let's say you have a page named MainPage.xaml. If you don't have view model already, create a new one and name it MainViewModel.cs. Define all public properties that will be used for binding.
Once you have your view model, create new file in a folder named SampleData and name it MainViewModelSampleData.xaml.
Now, in the MainPage.xaml add the following attribute to the page element:
d:DataContext={d:DesignData Source=SampleData/MainViewModelSampleData.xaml}
Also set Build Action for MainViewModelSampleData.xaml to DesignData.
Now, if you want to display data in your MainPage, you need to define all properties in the sample data file. For example:
// view model contains public properties Title of type string and Children of type
// PersonViewModel which contains properties Name and Age (string and int respectively)
<local:MainViewModel xmlns:local="clr-namespace:myapp"
Title="Title">
<local:MainViewModel.Children>
<local:ChildViewModel Name="John" Age="31" />
</local:MainViewModel.Children>
</local:MainViewModel>
You should now see your page filled with data in your design view. This way by using MVVM you can create mock data quickly. That will ensure that you can design your view around existing data without running the application.
Read more on the following links:
31 Days of Mango | Day #18: Using Sample Data
Modify sample data
Generate sample data
Using Blend Sample data at Design time and real data at Runtime
I now know how to do that.
If anyone if you guys ever stumble upon this problem, do this:
Copy all the XAML you wrote in the stackpanel of your itemtemplate
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
//...
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
And copy it up to <ListBox> //Here </ListBox>
There you can edit it in the designer.
And when you're done, just copy the code back to the StackPanel.
Is it possible to make a table having cells bound to several objects (for example, textboxes) without making use of DataGrid?
Example:
<TextBox Text="{Binding Path=FileName}" Width="300"></TextBox>
The DataContext for the textbox's container should contain a Property named FileName
You should note that your property should be wired to notify when it is changed. See the following for more information:
http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx