I have a simple ComboBox in my Silverlight 3 application. I want to populate it from an ObservableCollection. The list holds a class that has a Name(string), and a Selected(bool) property. The combo box has as many items as I have in the list, but I cannot seem to get the list data to appear.
Any help would be appreciated.
<ComboBox x:Name="cmbCategory" Grid.Column="3">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}"/>
<CheckBox IsChecked="{Binding Selected}"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
...
private class cmbCategoryClass
{
public string Name { get; set; }
public bool Selected { get; set; }
}
private ObservableCollection<cmbCategoryClass> _categories;
....
cmbCategory.DataContext = _categories;
cmbCategory.ItemsSource = _categories;
I can't tell from your code if this is a Codebehind or a ViewModel. I am guessing that you are actually populating the _categories list in code so that it contains at least one cmbCategoryClass object. Try removing the line that sets the DataContext to _categories as your ItemsSource may be looking for a _categories property on the DataContext Check the Output window in Visual Studio when running in debug mode for clues to data binding failures.
Related
I am trying to make a program that gives you a CRUD interface for List of any objects you give it. That includes:
Showing all of their properties inside a ListBox
The ability to insert a new object
The ability to update an object
The ability to delete an object
Keep in mind that, at the compile-time, I have no idea what kind of objects I am getting. For example, I want to have a TextBlock for each of the properties simply listed inside ListBox's DataTemplate. So how would I do the data binding if I don't know the name of the property? Also, how would I generate an insertion form when I don't know property names?
And finally, is it possible to do it using pure MVVM Pattern, without any Code-Behind?
Thanks
One option: Wrap PropertyInfo in a PropertyInfoViewModel so you can bind to it's value:
class PropertyInfoViewModel
{
Object CRUDObject { get; set; }
PropertyInfo PropertyInfo { get; set; }
Object Value {
get
{
return PropertyInfo.GetValue(CRUDObject);
}
set
{
PropertyInfo.SetValue(CRUDObject, value);
}
}
}
You could have an ObservableCollection in your CRUDObjectViewModel, populated when you create it or change the CRUD it's attached to (Look up reflection if confused by this).
Use a template selector to choose a particular editor to display for the PropertyInfoViewModel:
public class PropertyTypeTemplateSelector : DataTemplateSelector
{
public DataTemplate BooleanTemplate { get; set; }
public DataTemplate GuidTemplate { get; set; }
public DataTemplate StringTemplate { get; set; }
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
PropertyInfo propertyInfo = (item as PropertyInfoViewModel).PropertyInfo;
if (propertyInfo.PropertyType == typeof(Boolean))
{
return BooleanTemplate;
}
else if (propertyInfo.PropertyType == typeof(Guid))
{
return GuidTemplate;
}
else if (propertyInfo.PropertyType == typeof(String))
{
return StringTemplate;
}
return null;
}
}
You could use it like this:
<ListBox ItemsSource="{Binding Properties}">
<ListBox.Resources>
<DataTemplate x:Key="BooleanTemplate">
<CheckBox Content="{Binding PropertyInfo.Name}" IsChecked="{Binding Value}"/>
</DataTemplate>
<DataTemplate x:Key="GuidTemplate">
<StackPanel>
<TextBox Text="{Binding PropertyInfo.Name}"/>
<TextBox Text="{Binding Value, ValueConverter={StaticResources MyGuidConverter}}"/>
</StackPanel>
</DataTemplate>
<DataTemplate x:Key="StringTemplate">
<StackPanel>
<TextBox Text="{Binding PropertyInfo.Name}"/>
<TextBox Text="{Binding Value}"/>
</StackPanel>
</DataTemplate>
<DataTemplate x:Key="Null"/>
</ListBox.Resources>
<ListBox.ItemTemplateSelector>
<helpers:PropertyTypeTemplateSelector BooleanTemplate="{StaticResource BooleanTemplate}"
GuidTemplate="{StaticResource GuidTemplate}"
StringTemplate="{StaticResource StringTemplate}"/>
</ListBox.ItemTemplateSelector>
</ListBox>
Might have to think about how to deal with changes/updates though, as this isn't using NotifyPropertyChanged to keep the UI up to date.
I've not tested any of this, but it should work, I think.
This control WPFCrudControl may fit with your problem.
A generic WPF CrudControl implemented based on the MVVM pattern. It gives a huge productivity boost for straightforward CRUD operations (Add, Edit, Delete, Validate, Listing with sorting, paging and searching). The control abstracts both the UI and business logic, so it requires relatively minimal coding effort, while keeping it possible to customize its behavior.
I have a Movie class with a Dim _characters = New ObservableCollection(of String)
Characters is the associated property to get and set
How can i get characters to show up in the listBox using Binding?
So far i have the following, this isn't working as i don't know what to put instead of ToString.
<ListBox Name="cList" ItemsSource="{Binding Characters}">
<ItemsControl >
<ItemsControl.ItemTemplate >
<DataTemplate >
<TextBox Text="{Binding ToString}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ListBox>
I want them to be editable, hence a textbox.
i tried to bind Characters to TextBox directly, even that didn't work.
Edit :
in the code i have parentGrid1.DataContext = me.movies where
parent grid holds movies.
For those who are experiencing the exception
... binding requires path or xpath ...
You can bind the object directly this way:
<Label Content="{Binding .}" />
Change your TextBox binding to the following. I think it should work:
<TextBox Text="{Binding}"/>
This loads the item itself instead of a property or method output. Since the item is a string it should bind to the strings value.
You cannot perform two-way binding to ObservableCollection<string>. In order to make the strings editable you have to create a class with a string get/set property as the following class Foo:
public class Foo
{
string _text;
public Foo(string text)
{
_text = text;
}
public string Text
{
get { return _text; }
set { _text = value; }
}
}
Your Characters should then be of type ObservableCollection<Foo> and your XAML should be changed so that the textboxes are binding to Foo.Text:
<ListBox ItemsSource="{Binding Characters}" >
<ListBox.ItemTemplate >
<DataTemplate >
<TextBox Text="{Binding Text}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Just remove the ToString portion of the code.
Currently you are telling the program that you want to bind to an object called ToString
I take it that Characters is a public property. Debug and be sure that get is being called for Characters. If you have a the datacontext of the page/window to Movies then you need ItemsSource on the ListBox to be {Binding Path=Characters}
I am very new to WPF and testing some things that I would like to include in an application that I will be working on. I have a 2 row ListView (bound to a textbox) with the names Scott Guthrie and Jon Skeet in it. I am trying to select "Scott Guthrie" in the ListView and have it populate the TextBox. I want to be able to edit the text and tab off and have the ListView updated.
Edit:I removed the code since that really didn't add anything to the question.
Wow, that's really complicated what you've got there.
This can be accomplished in a very simple way. You need a model to represent the programmer, a view model to hold a list of programmers, and simple binding to take care of the rest.
The model:
public sealed class Programmer
{
public string Name { get; set; }
}
Its very simple. An object representing a programmer with a name. We must encapsulate the name within an object because strings are immutable in .NET. If you tried binding against a single string in a list of strings, changes wouldn't propagate.
The collection of programmers is kept in a ViewModel. In this case, I call it ViewModel, because I have no imagination. This view model contains everything that the view binds against. In this case, its the list of programmers.
public sealed class ViewModel
{
public ObservableCollection<Programmer> Programmers { get; private set; }
public ViewModel()
{
Programmers = new ObservableCollection<Programmer>();
}
}
The ViewModel is set as the DataContext of our view. The DataContext flows down the visual tree, and we can bind against it at any point.
public MainWindow()
{
var vm = new ViewModel();
vm.Programmers.Add(new Programmer { Name = "Jon Skeet" });
vm.Programmers.Add(new Programmer { Name = "Scott Guthrie" });
DataContext = vm;
InitializeComponent();
}
You can set the DataContext in any way you want; I'm doing it here for simplicity's sake.
In the UI, I simply bind the ListView against the list of Programmers in the ViewModel (the DataContext, unless otherwise stated, is the root of the binding path). I then bind the TextBox against the SelectedItem of the ListBox. You select a Programmer from the list, which then becomes the SelectedItem, which I can then change the Name of.
<Window
x:Class="Programmers.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:t="clr-namespace:Programmers"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ListBox
x:Name="list"
ItemsSource="{Binding Programmers}"
DisplayMemberPath="Name" />
<TextBox
Grid.Column="1"
VerticalAlignment="Top"
Text="{Binding SelectedItem.Name, ElementName=list}" />
</Grid>
</Window>
Simple, once you get the hang of it.
This works (except that you need to validate the textbox since you can enter any text.. a dropdown might be a better choice).
View:
<TabItem x:Name="RightTabPage" Header="RightModel" DataContext="{Binding Right}">
<StackPanel>
<TextBox Text="{Binding SelectedGuru}"/>
<ListView SelectedItem="{Binding SelectedGuru}" ItemsSource="{Binding Gurus}"/>
</StackPanel>
</TabItem>
ViewModel:
public class RightViewModel
{
public RightViewModel()
{
Gurus = new[] {"Scott Guthrie", "Jon Skeet"};
SelectedGuru = Gurus.First();
}
public string SelectedGuru { get; set; }
public IEnumerable<string> Gurus{ get; set; }
}
This is a very basic question. I have a grid, whose data context is bound to a entity framework service. I simply bound the context to service and I can see the data that is getting bound properly. Now, I want to change couple of coulmns to special controls. Like one column has true or false value and that column I want to display a radio button. One column is date value, I want to display date control. How would one go about doing it?
Thanks.
I'm not exactly sure how to do the Radio Button portion of this, but something like this may get you started:
<ListBox x:Name="LayoutRoot" ItemsSource="{Binding Collection}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Text}"/>
<CheckBox Content="True" IsChecked="{Binding Checked, Mode=TwoWay}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
In this case, you would have a checkbox being bound to the boolean value. I'm not exactly sure what you are using for a date control, but you should be able to place that in the stackpanel also and bind it to the dateproperty of your item.
In the above example, 'Collection' is an observable collection of 'MyObject' which is shown below:
MyObject.cs
public class MyObject
{
public string Text { get; set; }
public bool Checked { get; set; }
public bool InverseChecked { get; set; }
public DateTime Date { get; set; }
}
I also understand that you were using a grid, and I'm showing a ListBox. Not sure if this would work for you, but this is how we've approached it in the past.
Hope this helps!
I feel really stupid for asking this but I have been thrashing for over 8 hours. How do I get the Selected Item to show its text in my WPF combo box when selected?
Above is an option dialog that allows users to select and configure the available tournament displays. The problem is the selected combo box item shows the UserControl instead of the Display name.
On Window Loaded:
//_displayer is a private member populated using MEF
//[ImportMany(typeof (IDisplayer))]
//private IEnumerable<IDisplayer> _displayers;
DisplayTypeComboBox.ItemsSource = _displayers;
The ComboBox Xaml:
<ComboBox
Name="DisplayTypeComboBox"
Grid.Column="1"
Grid.ColumnSpan="2"
Grid.Row="1"
IsEditable="False"
SelectionChanged="DisplayTypeComboBox_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<ComboBoxItem Content="{Binding DisplayerName}" />
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
The IDisplayer:
public interface IDisplayer
{
string DisplayDataLocation { get; set; }
string DisplayerName { get; }
string DisplayerDescription { get;}
bool WatcherEnabled { get; }
UserControl View { get; }
string DisplayerImageLeft { get; set; }
string DisplayerImageRight { get; set; }
void Update();
}
I don't even want to think about how many hours I have spent trying to solve what should be a simple problem. Why is it so hard to get your selected text to appear as the selected value? I give up, WPF you have beat me into submission. I changed the control to a list box it takes up more room to display the selectable Items but at least it works.
<ListBox
Name="DisplayTypeComboBox"
Grid.Column="1"
Grid.ColumnSpan="2"
Grid.Row="1"
SelectionChanged="DisplayType_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<Label Content="{Binding DisplayerName}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I encountered the same thing. Took me a while too. :(
You should have used the ItemContainerStyle and not ItemTemplate.
Because ComboBox wraps the internal items with a ComboBoxItem - you basically wrapped the ComboBoxItem with another one.
Check what DisplayerName member actually contains. Most likely it contains the UserControl name instead of the Display name.
Try using a TextBlock to bind to the DisplayerName instead of a ComboboxItem. I believe that when you set the itemsource, the combo control will wrap the items inside comboboxitems controls automatically.
Edit: I misunderstood your question. Try setting the SelectionBoxItemTemplate.