Binding data to ComboBox WPF - wpf

I am newbie to WPF, and needs help to bind data into the ComboBox. The xaml file contains the tag below.
<UserControl x:Class="SKAT.Postfordeler.Client.UI.View.ChooseInboxView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="42" d:DesignWidth="598">
<Grid>
<StackPanel Orientation="Horizontal">
<ComboBox Name="_currentInbox" Width="180" Margin="5" Height="22" DataContext="{Binding}" />
<Label Content="Et job kører allerede i denne indbakke (1500 ud af 1700 poster behandlet)" Name="_currentProcess" Margin="5" Height="25" />
</StackPanel>
</Grid>
//Inbox class , this class was implemented in seperate project
namespace SKAT.Postfordeler.Shared.DataTypes
{
[DataContract]
public class Inbox
{
[DataMember]
public String Id { get; set; }
[DataMember]
public String Folder { get; set; }
[DataMember]
public Rule Rules { get; set; }
}
}
//This code is located in the controller, the Activate method will fire when the MainWindow was executed
public void Activate()
{
var configuration = _configurationManager.GetConfiguration();// this method gets the xaml file settings
_chooseInboxView.FillInboxes(configuration.Inboxes); // Inboxes data binds to combobox
}
and in the View code behind, I created a method to bind the data which contains a type of list
public void FillInboxes(List<Inbox> inboxes)
{
DataContext = inboxes;
}
But it won't works,Any help please?

I assume your Inbox class consists of two properties (for simplicity), but there may be any number of them:
public class Inbox
{
public int ID { get; set; }
public string Text { get; set; }
}
You write a DataTemplate, for example:
<Grid.Resources>
<DataTemplate x:Key="InboxTemplate">
<WrapPanel>
<TextBlock Text="{Binding Path=ID}"/>
<TextBlock>:</TextBlock>
<TextBlock Text="{Binding Path=Text}"/>
</WrapPanel>
</DataTemplate>
</Grid.Resources>
Then correct your ComboBox declaration like:
<ComboBox Name="_currentInbox" Width="180" Margin="5" Height="22" ItemsSource="{Binding}" ItemTemplate="{StaticResource InboxTemplate}" />
Finally you set DataContext of your ComboBox to your List<Inbox>:
public void FillInboxes(List<Inbox> inboxes)
{
_currentInbox.DataContext = inboxes;
}
EDIT: As you've asked for a simpler solution, you can just override ToString() method of your Inbox class:
protected override string ToString()
{
return ID.ToString() + ":" + Text;
}

Instead of DataContext={Binding} you should have ItemsSource={Binding}.
The data context for any frameworkelement in the visual tree is by default {Binding}.
<ComboBox Name="_currentInbox"
SelectedItem="Hoved"
Width="180"
Margin="5"
Height="22"
DisplayMemberPath="Name"
ItemSource="{Binding}" />
Also for the combobox to display text of the items correctly I suppose you need DisplayMemberPath too. I assumed the property from Inbox class that you need to display is Name. Please replace with your relevant property name.

If your Inbox class is like,
public class Inbox
{
public int ID { get; set; }
public string Text { get; set; }
}
And if you do not want to change your xmal, the code behind method should be like this,
public void FillInboxes(List<Inbox> inboxes)
{
_currentInbox.DisplayMemberPath = "Text"; // To display the 'Text' property in the combobox dropdown
//_currentInbox.DisplayMemberPath = "ID"; // To display the 'ID' property in the combobox dropdown
_currentInbox.DataContext = inboxes;
}

Related

ArgumentNullException thrown from combobox in my custom activity

I have a simple custom activity demo of WF.
The XAML code:
<sap:ActivityDesigner x:Class="ActivityDesignerLibrary2.ActivityDesigner1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sap="clr-namespace:System.Activities.Presentation;assembly=System.Activities.Presentation"
xmlns:sapv="clr-namespace:System.Activities.Presentation.View;assembly=System.Activities.Presentation">
<Grid>
<ComboBox x:Name="comboBox"
ItemsSource="{Binding Path=ModelItem.Values}"
SelectedValue="{Binding Path=ModelItem.Value, Mode=TwoWay}"
HorizontalAlignment="Left" Margin="36,0,0,0" VerticalAlignment="Top" Width="120"/>
</Grid>
</sap:ActivityDesigner>
The code behide:
[Designer(typeof(ActivityDesignerLibrary2.ActivityDesigner1))]
public class Class1 : CodeActivity
{
public List<string> Values { get; set; }
public string Value { get; set; }
public Class1()
{
Values = new List<string>() { "V1", "V2", "V3"};
Value = "V2";
}
protected override void Execute(CodeActivityContext context)
{
}
}
When I drag this custom activity into a workflow, an error messagebox is popped up.
I found it's SelectedValue make the error, but is there anything error and how to fix it?

WPF Specifying HierarchicalDataTemplate for Interface

I've found a really strange quirk in WPF. If I specify a DataTemplate for an interface, it will work if defined inside an ItemsControl.ItemTemplate, but will not work if defined inside ItemsControl.Resrouces.
Concrete example:
I have a tree structure I want to represent. All items in the tree implement IHardware, but they do not necessarily have a common base type. If I define a HierarchicalDataTemplate for IHardware inside TreeView.ItemTemplate, everything works swimmingly. If I define the template inside TreeView.Resources, it never gets used/applied. The following shows the same data in 2 columns, the first column works as expected, the second column does not.
<Window x:Class="WPFInterfaceBinding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:self ="clr-namespace:WPFInterfaceBinding"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<!-- Works -->
<Border
Grid.Column="0"
Background="Gray">
<TreeView
ItemsSource="{Binding Hardware}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate
DataType="{x:Type self:IHardware}"
ItemsSource="{Binding SubHardware}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
</Border>
<!-- Doesn't work -->
<Border
Grid.Column="1"
Background="Gray">
<TreeView
ItemsSource="{Binding Hardware}">
<TreeView.Resources>
<HierarchicalDataTemplate
DataType="{x:Type self:IHardware}"
ItemsSource="{Binding SubHardware}">
<TextBlock Text="{Binding Path=Name}" />
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>
</Border>
</Grid>
</Window>
Note that in the second column, nothing has changed except TreeView.ItemTemplate -> TreeView.Resources
Why is this the case? How can I get the template to work when inside Resources? I imagine I can work around this using a DataTemplateSelector, but first I'm curious if there's a way to actually get it working as expected.
Code behind, for completeness
using System.Windows;
namespace WPFInterfaceBinding
{
public partial class MainWindow : Window
{
public IHardware[] Hardware { get; private set; }
public MainWindow ()
{
Hardware = InitializeHardware();
InitializeComponent();
}
private IHardware[] InitializeHardware ()
{
return new Hardware[] {
new Hardware("Component 1", new Hardware[] {
new Hardware("Sub Component 1"),
new Hardware("Sub Component 2")
}),
new Hardware("Component 2", new Hardware[] {
new Hardware("Sub Component 3"),
new Hardware("Sub Component 4")
})
};
}
}
public class Hardware : IHardware
{
public string Name { get; set; }
public IHardware[] SubHardware { get; set; }
public Hardware ( string name, Hardware[] subHardware = null )
{
Name = name;
SubHardware = subHardware ?? new Hardware[0];
}
}
public interface IHardware
{
string Name { get; set; }
IHardware[] SubHardware { get; set; }
}
}
Additional information:
I can't simply use ItemTemplate because in my actual usage scenario there will be non-IHardware items mixed in using a CompositeCollection so I need multiple templates.
I can't change the types of the collections from IHardware to something concrete because I'm displaying data from code I don't control.
This is just example code, not representative of any design patterns actually in use.
Defining the template inside TreeView.Resources works just fine if the type is changed from IHardware to Hardware.
Turns out, WPF just doesn't like binding to interfaces. The only work around I could figure out was to use a DataTemplateSelector.
public class OHMTreeTemplateSelector : DataTemplateSelector
{
public HierarchicalDataTemplate HardwareTemplate { get; set; }
public DataTemplate SensorTemplate { get; set; }
public override DataTemplate SelectTemplate ( object item, DependencyObject container )
{
if ( item is IHardware ) return HardwareTemplate;
else if ( item is ISensor ) return SensorTemplate;
return base.SelectTemplate(item, container);
}
}
Though, for other reasons I ended up creating a separate ViewModel for the data that exposes it through concrete types, circumventing this issue.

ListBox DataTemplate for dynamically loaded type

I have a sample MVVM WPF application and I'm having problems creating DataTemplates for my dynamically loaded model. Let me try explain:
I have the following simplified classes as part of my Model, which I'm loading dynamically
public class Relationship
{
public string Category { get; set; }
public ParticipantsType Participants { get; set; }
}
public class ParticipantsType
{
public ObservableCollection<ParticipantType> Participant { get; set; }
}
public class ParticipantType
{
}
public class EmployeeParticipant : ParticipantType
{
public EmployeeIdentityType Employee { get; set; }
}
public class DepartmentParticipant : ParticipantType
{
public DepartmentIdentityType Department { get; set; }
}
public class EmployeeIdentityType
{
public string ID { get; set; }
}
public class DepartmentIdentityType
{
public string ID { get; set; }
}
Here is how my View Model looks like. I created a generic object Model property to expose my Model:
public class MainViewModel : ViewModelBase<MainViewModel>
{
public MainViewModel()
{
SetMockModel();
}
private void SetMockModel()
{
Relationship rel = new Relationship();
rel.Category = "213";
EmployeeParticipant emp = new EmployeeParticipant();
emp.Employee = new EmployeeIdentityType();
emp.Employee.ID = "222";
DepartmentParticipant dep = new DepartmentParticipant();
dep.Department = new DepartmentIdentityType();
dep.Department.ID = "444";
rel.Participants = new ParticipantsType() { Participant = new ObservableCollection<ParticipantType>() };
rel.Participants.Participant.Add(emp);
rel.Participants.Participant.Add(dep);
Model = rel;
}
private object _Model;
public object Model
{
get { return _Model; }
set
{
_Model = value;
NotifyPropertyChanged(m => m.Model);
}
}
}
Then I tried creating a ListBox to display specifically the Participants Collection:
<ListBox ItemsSource="{Binding Path=Model.Participants.Participant}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<Expander Header="IdentityFields">
<!-- WHAT TO PUT HERE IF PARTICIPANTS HAVE DIFFERENT PROPERTY NAMES -->
</Expander>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
The problem is:
I don't know how to create a template that can handle both type of ParticipantTypes, in this case I could have EmployeeParticipant or DepartmentParticipant so depending on that, the data binding Path would be set to Employee or Department properties accordingly
I though about creating a DataTemplate for each type (e.g. x:Type EmployeeParticipant) but the problem is that my classes in my model are loaded dynamically at runtime so VisualStudio will complain that those types don't exist in the current solution.
How could I represent this data in a ListBox then if my concrete types are not known at compile time, but only at runtime?
EDIT: Added my test ViewModel class
You can still create a DataTemplate for each type but instead of using DataType declarations to have them automatically resolve you can create a DataTemplateSelector with a property for each template (assigned from StaticResource in XAML) that can cast the incoming data item to the base class and check properties or otherwise determine which template to use at runtime. Assign that selector to ListBox.ItemTemplateSelector and you'll get similar behavior to what DataType would give you.
That's not a good view-model. Your view-model should be view-centric, not business-centric. So make a class that can handle all four cases from a visual perspective, then bridge your business classes over to that view-model.
EDIT:
Working off your code:
<ListBox ItemsSource="{Binding Path=Model.Participants}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<Expander Header="IdentityFields">
<TextBlock Text={Binding Id} />
<TextBlock Text={Binding Name} />
</Expander>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I changed the binding, I assume that was a mistake?
I would create a ViewModel for Participant:
public class Participant_VM : ViewModelBase
{
private string _name = string.Empty;
public string Name
{
get
{
return _name ;
}
set
{
if (_name == value)
{
return;
}
_name = value;
RaisePropertyChanged(() => Name);
}
private string _id= string.Empty;
public string Id
{
get
{
return _id;
}
set
{
if (_id== value)
{
return;
}
_id = value;
RaisePropertyChanged(() => Id);
}
}
}
Modify the ListBox as follows.
<ListBox ItemsSource="{Binding Model.Participants.Participant}">
<ListBox.Resources>
<DataTemplate DataType="{x:Type loc:DepartmentParticipant}">
<Grid>
<TextBlock Text="{Binding Department.ID}"/>
</Grid>
</DataTemplate>
<DataTemplate DataType="{x:Type loc:EmployeeParticipant}">
<Grid>
<TextBlock Text="{Binding Employee.ID}"/>
</Grid>
</DataTemplate>
</ListBox.Resources>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<Expander Header="IdentityFields">
<!-- WHAT TO PUT HERE IF PARTICIPANTS HAVE DIFFERENT PROPERTY NAMES -->
<ContentPresenter Content="{Binding }"/>
</Expander>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Edit:
loc refers to the namespace in which the DepartmentParticipant and EmployeeParticipant are present. Hope you are familiar with adding namespaces.

Control number of display buttons through binding

I wasn't sure the best way to word the title and couldn't find a related question, but if there is one then kindly direct me to it.
I'm trying to create a tender screen where the number of buttons displayed will be determined by how many types of tenders the user has setup (Cash, Check, Credit, Debit, Gift Card, etc).
So if I had a class like this:
public class TenderType
{
public string DisplayName { get; set; }
// ... other implementation details
}
And on my DataContext I have a TenderTypes collection declared like so:
public ObservableCollection<TenderType> TenderTypes { get; private set; }
Then how might I go about making my view udpate the number of buttons shown depending on how many TenderType instances are in the collection, and bind their Text properties to the DisplayName of the appropriate item in the collection?
You could use an ItemsControl and create a datatemplate for your TenderType to display a Button.
This way it will only show the buttons in your list
Xaml:
<Window x:Class="WpfApplication8.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication8"
Title="MainWindow" Height="105" Width="156" Name="UI">
<Window.Resources>
<DataTemplate DataType="{x:Type local:TenderType}">
<Button Content="{Binding DisplayName}" />
</DataTemplate>
</Window.Resources>
<Grid DataContext="{Binding ElementName=UI}">
<ItemsControl ItemsSource="{Binding TenderTypes}"/>
</Grid>
</Window>
Code:
public partial class MainWindow : Window
{
private ObservableCollection<TenderType> _sourceData = new ObservableCollection<TenderType>();
public MainWindow()
{
InitializeComponent();
TenderTypes.Add(new TenderType { DisplayName = "Stack" });
TenderTypes.Add(new TenderType { DisplayName = "Overflow" });
}
public ObservableCollection<TenderType> TenderTypes
{
get { return _sourceData; }
set { _sourceData = value; }
}
}
public class TenderType
{
public string DisplayName { get; set; }
}
Result:

Silverlight Control Toolkit TreeView not rendering items

I'm trying to build a SL app with a TreeView in it. Here's my XAML:
<UserControl xmlns:controls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Toolkit"
xmlns:tkwin="clr-namespace:System.Windows;assembly=System.Windows.Controls.Toolkit"
xmlns:basics="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="SL.MyApp.Page"
Width="800" Height="600">
<controls:DockPanel>
<controls:TreeView Name="siteTree" controls:DockPanel.Dock="Left" Width="150">
<controls:TreeView.ItemTemplate>
<tkwin:HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}"/>
</StackPanel>
</tkwin:HierarchicalDataTemplate>
</controls:TreeView.ItemTemplate>
</controls:TreeView>
<basics:TabControl controls:DockPanel.Dock="Right" TabStripPlacement="Top">
<basics:TabItem Header="Sites"></basics:TabItem>
<basics:TabItem Header="Lists"></basics:TabItem>
<basics:TabItem Header="Users"></basics:TabItem>
</basics:TabControl>
</controls:DockPanel>
</UserControl>
And the relevant codebehind:
namespace SL.MyApp
{
public partial class Page : UserControl
{
private ObservableCollection<WebDescriptor> _webHierarchy = new ObservableCollection<WebDescriptor>();
public Page(WebsSvc.WebsSoapClient websClient)
{
InitializeComponent();
siteTree.ItemsSource = _webHierarchy;
websClient.GetWebCollectionCompleted
+= new EventHandler<SL.SiteBuilder.WebsSvc.GetWebCollectionCompletedEventArgs>(websClient_GetWebCollectionCompleted);
websClient.GetWebCollectionAsync();
// TODO: some kind of spinner or progress bar needs to be started.
}
void websClient_GetWebCollectionCompleted(object sender, SL.SiteBuilder.WebsSvc.GetWebCollectionCompletedEventArgs e)
{
foreach (XElement xe in e.Result.Elements())
{
_webHierarchy.Add(ServiceObjectParser<WebDescriptor>.Parse(xe));
}
}
}
}
Update: The WebDescriptor class:
public class WebDescriptor
{
public string Title { get; set; }
public string Url { get; set; }
public List<WebDescriptor> Children { get; set; }
}
My problem is that nothing renders in the TreeView at all. I have verified that the results obtained in websClient_GetWebCollectionCompleted are valid and correct, but....nothing.
Any ideas?
in websClient_GetWebCollectionCompleted:
siteTree.ItemsSource = _webHierarchy;
Also, change your binding on the TextBlock in the Treeview to be {Binding Title}
After looking at the binding trace output, I finally realized I was trying to bind to a field instead of a property.
Doh!

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