I want to execute some function when user selects a different value in the combo box.
I am using MVVM pattern .
Any Idea how I Data Bind in this case ?
bind to a property on SelectedItem.
in the property's setter, execute your function.
SelectedItem="{Binding Path=SomeProperty}"
You'd want to either bind to the SelectedValue, SelectedItem, or SelectedIndex depending on what you want to do:
public class MyViewModel : INotifyPropertyChanged
{
public ObservableCollection<MyObj> MyCollection { get; private set; }
private MyObj _theItem;
public MyObj TheItem
{
get { return _theItem; }
set
{
if (Equals(value, _theItem)) return;
_theItem= value;
//Or however else you implement this...
OnPropertyChanged("TheItem");
//Do something here.... OR
//This will trigger a PropertyChangedEvent if you're subscribed internally.
}
}
private string _theValue;
public string TheValue
{
get { return _theValue; }
set
{
if (Equals(value, _theValue)) return;
_theValue= value;
OnPropertyChanged("TheValue");
}
}
private int _theIndex;
public int TheIndex
{
get { return _theIndex; }
set
{
if (Equals(value, _theIndex)) return;
_theIndex = value;
OnPropertyChanged("TheIndex");
}
}
}
public class MyObj
{
public string PropA { get; set; }
}
<!-- Realistically, you'd only want to bind to one of those -->
<!-- Most likely the SelectedItem for the best usage -->
<ItemsControl ItemsSource="{Binding Path=MyCollection}"
SelectedItem="{Binding Path=TheItem}"
SelectedValue="{Binding Path=TheValue}"
SelectedIndex="{Binding Path=TheIndex}"
/>
Related
I'm sure this has already been asked, but I'm still new to MVVM and WPF, and not too sure what I should be searching for.
I have a viewmodel which includes items in a Model, as well as some additional temporary data items which will all be passed to a process.start(). I have a stackpanel of textbox, and want to allow the user to type in a "ModelName", and if existing, The ViewModel will get and set "TemplateName" associated with the ModelName.
I'm a bit lost on how to implement this. Do I need to create a completely separate ViewModel, which then goes and extracts data from ModelViewModel? Do I just write some code under ModelName's set, where it can validate, query, and set TemplateName?
Model:
public partial class Model
{
public string ModelName { get; set; }
public virtual Template Template { get; set; }
and ViewModel, which takes the Model, and some temporary data:
public class LauncherViewModel:ViewModelBase
{
public LauncherViewModel()
{
_ESTContext = new ESTContext();
Models = new ObservableCollection<Model>(_ESTContext.Models);
}
private ESTContext _ESTContext;
private string _modelname;
private string _serialno;
private string _sonumber;
private string _templatename;
private string _outputname;
private Model _selectedmodel;
public ObservableCollection<Model> Models { get; set; }
public string ModelName
{
get { return _modelname; }
set
{
if (!string.Equals(_modelname, value))
{
_modelname = value;
};
}
}
public string TemplateName { get { return _templatename; }}
public string SerialNo { get { return _serialno; } }
public string SONumber { get { return _sonumber; } }
public string OutputName { get { return _outputname; } }
public Model SelectedModel
{
get { return _selectedmodel; }
set
{
if (_selectedmodel != value)
{
_selectedmodel = value;
}
}
}
}
My View:
<DockPanel>
<StackPanel Margin="0,78,0,68" Width="233" DataContext="{Binding Models}">
<ComboBox IsEditable="True" Text="{Binding ModelName}" SelectedItem="{Binding SelectedModel}"/>
<TextBox Height="23" TextWrapping="Wrap" Text="{Binding SONumber}"/>
<TextBox Height="23" TextWrapping="Wrap" Text="{Binding SerialNumber}"/>
<Button Content="Button"/>
</StackPanel>
</DockPanel>
For your gui to update you must implement INotifyPropertyChanged and a call to it on all your bound properties.
// basic base class for your models, you a
public class ModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator] // remove if you are not using R#
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
// your model
public class Model : ModelBase
{
private string modelName;
private Template template;
public string ModelName
{
get { return modelName; }
set
{
if (value == modelName) return;
modelName = value;
OnPropertyChanged();
}
}
public virtual Template Template
{
get { return template; }
set
{
if (Equals(value, template)) return;
template = value;
OnPropertyChanged();
}
}
}
View:
<DockPanel>
<StackPanel Margin="0,78,0,68" Width="233">
<ComboBox IsEditable="True" Text="{Binding ModelName, Mode='TwoWay'}" SelectedItem="{Binding SelectedModel}" ItemsSource="{Binding Models}"/>
<TextBox Height="23" TextWrapping="Wrap" Text="{Binding SONumber Mode='TwoWay'}"/>
<TextBox Height="23" TextWrapping="Wrap" Text="{Binding SerialNumber Mode='TwoWay'}"/>
<Button Content="Button"/>
</StackPanel>
Note the Mode='TwoWay' this makes the GUI change the values in your viewmodel, rather than just display them. So you need to set that on everything that's supposed to be editable as above. The default behaviour of WPF is that when a control looses focus it will update the bound property, if you set UpdateSourceTrigger='PropertyChanged' the property will be updated each time ie a letter is entered in a text box. I'll leave that part to you, but you will have to do it in your vm! At minimum the properties SONumber,SerialNumber and Models(if it's ref. changes).
VM: I assume you use galasoft here
public class LauncherViewModel : ViewModelBase
{
private ESTContext _ESTContext;
private string _templatename;
private string _modelname;
private string serialNumber;
private string _outputname;
private string modelName;
private ObservableCollection<Model> models;
private Model selectedModel;
private string soNumber;
public LauncherViewModel()
{
// dangerous ;)
_ESTContext = new ESTContext();
Models = new ObservableCollection<Model>(_ESTContext.Models);
}
public ObservableCollection<Model> Models
{
get { return models; }
set
{
if (Equals(value, models)) return;
models = value;
RaisePropertyChanged();
}
}
public string ModelName
{
get { return modelName; }
set
{
if (value == modelName) return;
modelName = value;
RaisePropertyChanged();
}
}
public string TemplateName { get { return _templatename; }}
public string SerialNumber // Note you spelled this wrong in your xaml. SONumber
{
get { return serialNumber; }
set
{
if (value == serialNumber) return;
serialNumber = value;
RaisePropertyChanged();
}
}
public string SONumber
{
get { return soNumber; }
set
{
if (value == soNumber) return;
soNumber = value;
RaisePropertyChanged();
}
}
public string OutputName { get { return _outputname; } }
public Model SelectedModel
{
get { return selectedModel; }
set
{
if (Equals(value, selectedModel)) return;
selectedModel = value;
RaisePropertyChanged();
}
}
}
A cool litle thing if you are using galasoft or sim together with R#.
public class YourViewModelBase : ViewModelBase
{
[NotifyPropertyChangedInvocator] // alt + enter = convert auto property to prop
// with backing field and change notification :)
override protected void RaisePropertyChanged([CallerMemberName] string propertyName = null)
{
base.RaisePropertyChanged(propertyName);
}
// .. :)
}
Cheers,
Stian
If I havent misunderstood your question , Bind Models to ItemsSource of ComboBox instead of Binding it to DataContext of StackPanel
Remove DataContext binding
<StackPanel Margin="0,78,0,68" Width="233" >
Bind Itemssource of ComboBox to Models and you will also have to specify DisplayMemberPath to the property of Model that you want to display in ComboBox.
<ComboBox IsEditable="True" ItemsSource="{Binding Models}" Text="{Binding ModelName}" SelectedItem="{Binding SelectedModel}"/>
And I am assuming you are setting DataContext of window to instance of LauncherViewModel class.
You need to raise the property changed event on properties you bind to i.e.:
private string _ModelName;
public string ModelName
{
get { return _ModelName; }
set
{
if (_ModelName != value)
{
_ModelName = value;
RaisePropertyChanged("ModelName");
}
}
}
In your base view model you need something like this (make sure you implement INotifyPropertyChanged):
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
In the constructor or loaded event of your view add this:
DataContext = new LauncherViewModel();
What can I do if I want to bind to some property which is already bound to something else?
In my case, I got a window which has a TextBox. The Text property of this TextBox is data bound to a combo box to it's selectedItem. My Window class got a public string property which I want to update with whatever value is in the TextBox so I wanted to data bind with the Text property but as I said, it's already bound.
How can I update my property with the text in TextBox? Must it use a routed event of TextChanged or can I do it via Xaml?
Also specifically with properties you define them yourself in your window.cs ... how can you bind them to the TextBox.Text? I tried doing it with the <Window> declaration, meaning <Window MyProperty={Binding ...} /> but the property is not recognized there. Why and how do I do it?
You could solve this easily using the MVVM pattern.
ViewModel:
public class ChooseCategoryViewModel : ViewModelBase
{
private string[] _categories =
{ "Fruit", "Meat", "Vegetable", "Cereal" };
public string[] Categories
{
get { return _categories; }
}
private string _selectedCategory;
public string SelectedCategory
{
get { return _selectedCategory; }
set
{
_selectedCategory = value;
OnPropertyChanged("SelectedCategory");
if (value != null && CategoryName != value)
CategoryName = value;
}
}
private string _categoryName;
public string CategoryName
{
get { return _categoryName; }
set
{
_categoryName = value;
OnPropertyChanged("CategoryName");
if (Categories.Contains(value))
{
SelectedCategory = value;
}
else
{
SelectedCategory = null;
}
}
}
}
XAML:
<ComboBox ItemsSource="{Binding Categories}"
SelectedItem="{Binding SelectedCategory}" />
<TextBox Text="{Binding CategoryName}" />
I am not able to find out Why is combo box binding not working?
I have a view model which looks like (2 properties)
public ProcessMaintenanceDataObject CurrentProcess
{
get
{
return _CurrentProcess;
}
set
{
_CurrentProcess = value;
OnPropertyChanged("CurrentProcess");
}
}
public ObservableCollection<ProcessMaintenanceDataObject > Processes
{
get
{
return _Processes;
}
set
{
_Processes = value;
OnPropertyChanged("Processes");
}
}
public ObservableCollection<FolderInfo> Folders
{
get
{
return _folders;
}
set
{
_folders = value;
OnPropertyChanged("Folders");
}
}
The following is the ProcessMaintenanceDataObject definition
[DataMember]
public string ProcessName
{
get
{
return _ProcessName;
}
set
{
_ProcessName = value;
OnPropertyChanged("ProcessName");
}
}
[DataMember]
public string Id
{
get
{
return _Id;
}
set
{
_Id = value;
OnPropertyChanged("Id");
}
}
[DataMember]
public string FolderId
{
get
{
return _FolderId;
}
set
{
_FolderId = value;
OnPropertyChanged("FolderId");
}
}
[DataMember]
public FolderInfo Folder
{
get
{
return _Folder;
}
set
{
_Folder = value;
if (_Folder != null)
FolderId = _Folder.FolderId;
OnPropertyChanged("Folder");
}
}
The FolderInfo class has FolderName and FolderId Property.
I have a method in viewmodel which fills the Processes.
In my view I have structure something like, I have a treeview which will be bound to Processes and while selecting any of the item from the treeview, i need to allow user to edit that entity.
In the view the combo box binding is as:
<ComboBox ItemsSource="{Binding Path=Folders, Mode=OneWay}"
DisplayMemberPath="FolderName"
SelectedItem="{Binding Source={StaticResource viewModel}, Path=CurrentProcess.Folder, Mode=TwoWay}">
...
This binding doesn't work I mean when I select any object from the tree it fills other information like ProcesName in the textBox but it doesn't make the Folder object as the selected item in combobox, however the combo box will be filled.
Any suggestion.
Do refer this:
If you want to bind a ComboBox to your folders property in two way mode with edit support,
Then you should define data template for your combo box and then bind properties of FolderInfo class to those text boxes
Binding display member path will not solve your problem
I'd suggest you to change DisplayMemberPath with appropriate DataTemplate:
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding FolderName}">
</StackPanel>
<DataTemplate>
This will fix SelectedItem context.
Maybe just maybe, your Folderinfo class is not a notificationObject. If it is the case make sure it implements INotifyPropertyChange.
you have to use SelectedValuePath and SelectedValue instead of SelectedItem like below,
<ComboBox ItemsSource="{Binding Path=Folders, Mode=OneWay}"
DisplayMemberPath="FolderName"
SelectedValuePath="FolderId"
SelectedValue="{Binding Path=FolderId, Mode=TwoWay}">
SelectedItem binds the whole object whereas SelectedValue binds only particular properties of the object.
I have one model that implements INotifyPropertyChanged through BaseModel class.
It has other model as element inside of it.
class SIDPoslJavnaUstanova : BaseModel
{
private int? _sid_posl_javna_ustanova_id;
...
private decimal? _udaljenost;
private SIDJavnaUstanova _sid_javna_ustanova;
public SIDJavnaUstanova SidJavnaUstanova
{
get { return _sid_javna_ustanova; }
set {
if (_sid_javna_ustanova != value)
{
_sid_javna_ustanova = value;
if (_sid_javna_ustanova != null)
{
_sid_javna_ustanova_id = _sid_javna_ustanova.SidJavnaUstanovaId;
}
else
{
_sid_javna_ustanova_id = null;
}
RaisePropertyChanged("SidJavnaUstanova");
}
}
}
I have viewmodel that has observable collection of this model objects.
class BaseViewModel<T> : ObservableObject
{
private ObservableCollection<T> _elements = new ObservableCollection<T>();
public ObservableCollection<T> Elements
...
class SIDPoslJavnaUstanovaViewModel : BaseViewModel<SIDPoslJavnaUstanova>
{
}
}
And finally, mainviewmodel that is bound to view:
class MainViewModel : BaseViewModel<Store>
{
private SIDJavnaUstanovaViewModel _sidJavnaUstanovaViewModel;
private SIDJavnaUstanova _sidJavnaUstanova;
public SIDPoslJavnaUstanovaViewModel SidPoslJavnaUstanovaViewModel
{
get { return _sidPoslJavnaUstanovaViewModel; }
set
{
if (_sidPoslJavnaUstanovaViewModel != value)
{
_sidPoslJavnaUstanovaViewModel = value;
RaisePropertyChanged("SidPoslJavnaUstanovaViewModel");
}
}
}
public SIDJavnaUstanovaViewModel SidJavnaUstanovaViewModel
{
get { return _sidJavnaUstanovaViewModel; }
set
{
if (_sidJavnaUstanovaViewModel != value)
{
_sidJavnaUstanovaViewModel = value;
RaisePropertyChanged("SidJavnaUstanovaViewModel");
}
}
}
SidJavnaUstanova is only used to populate combobox, and to bind to object when choosen.
I have combobox in datagrid, that has mulitple lines. Element is SIDJAVNAUSTANOVA , and dropdown is SIDJAVNAUSTANOVAVIEWMODEL.
Dropdown is SIDJAVNAUSTANOVAVIEWMODEL.ELEMENTS
(cannot show you picture not enough reputation)
<src:BaseWindow.Resources>
<viewmod:MainViewModel x:Key="StoreViewM"/>
</src:BaseWindow.Resources>
<DataGrid.Columns>
<DataGridTemplateColumn Width="140" Header="{StaticResource name}">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Path=SidJavnaUstanovaViewModel.Elements,
Source={StaticResource StoreViewM}}"
SelectedItem="{Binding Path=SidJavnaUstanova,UpdateSourceTrigger=PropertyChanged,
Mode=TwoWay}"
DisplayMemberPath="Naziv"
SelectedValue="{Binding Path=SidJavnaUstanova, Mode=TwoWay}">
</ComboBox>
...
Everything is working fine except when combobox is changed, element SIDJavnaUstanova of object SIDPoslJavnaUstanova is changed, and I can catch this in its model property. But what I must have, is to catch change of this SidJavnaUstanova in viewmodel, so I can implement check-out if there are duplicates of sidjavnaustanova in sidposljavnaustanovaviewmodel.elements. I cannot realize how to do that.
Something like
SIDPoslJavnaUstanova.Elements.??? SIDJavnaUstanova
I cannot do this because elements is observable collection.
Maybe it is a bad model, please suggest something or help with current code.
You need to a) specify source for SelectedItem b) bind SelectedItem to the property of the same type, as elements in your collection (i.e. SIDPoslJavnaUstanova in your case).
This should work, i guess:
<ComboBox ItemsSource="{Binding Path=SidJavnaUstanovaViewModel.Elements,
Source={StaticResource StoreViewM}}"
SelectedItem="{Binding Path=SelectedModel,UpdateSourceTrigger=PropertyChanged,
Mode=TwoWay, Source={StaticResource StoreViewM}}"
DisplayMemberPath="Naziv">
</ComboBox>
.........................................
//MainViewModel
public SIDPoslJavnaUstanova SelectedModel
{
get { return _selectedModel; }
set
{
if (_selectedModel != value)
{
_selectedModel = value;
RaisePropertyChanged("SelectedModel");
}
}
}
And yes, this is some awful design.
I am just starting with MVVM and have hit a hurdle that I hope someone can help me with. I am trying to create a simple View with 2 listboxes. A selection from the first listbox will populate the second list box. I have a class created that stores the information I want to bind to.
MyObject Class (Observable Object is just a base class that implements INotifyPopertyChanged)
public class MyObject : ObservableObject
{
String _name = String.Empty;
ObservableCollection<MyObject> _subcategories;
public ObservableCollection<MyObject> SubCategories
{
get { return _subcategories; }
set
{
_subcategories = value;
RaisePropertyChanged("SubCategories");
}
}
public String Name
{
get { return _name; }
set
{
_name = value;
RaisePropertyChanged("Name");
}
}
public MyObject()
{
_subcategories = new ObservableCollection<EMSMenuItem>();
}
}
In my viewmodel I have two ObservableCollections created
public ObservableCollection<EMSMenuItem> Level1MenuItems { get; set; }
public ObservableCollection<EMSMenuItem> Level2MenuItems { get; set; }
In my constructor of the ViewModel I have:
this.Level1MenuItems = new ObservableCollection<EMSMenuItem>();
this.Level2MenuItems = new ObservableCollection<EMSMenuItem>();
this.Level1MenuItems = LoadEMSMenuItems("Sample.Xml");
That works fine for the Level1 items and they correctly show in the View. However I have a command that gets called when the user clicks an item in the listbox, which has the following:
Level2MenuItems = ClickedItem.SubCategories;
For some reason this does not update the UI of the second listbox. If I put a breakpoint at this location I can see that Level2MenuItems has the correct information stored in it. If I write a foreach loop and add them individually to the Level2MenuItems collection then it does display correctly.
Also as a test I added the following to the constructor:
Level2MenuItems = Level1MenuItems[0].SubCategories;
And that updated correctly.
So why would the code work as expected in the constructor, or when looping through, but not when a user clicks on an item in the listbox?
You need to raise the change notification on the Level2MenuItems property.
Instead of having
public ObservableCollection<EMSMenuItem> Level2MenuItems { get; set; }
you need
private ObservableCollection<EMSMenuItem> _level2MenuItems;
public ObservableCollection<EMSMenuItem> Level2MenuItems
{
get { return _level2MenuItems; }
set
{
_level2MenuItems = value;
RaisePropertyChanged(nameof(Level2MenuItems));
}
}
The reason the former works in the constructor is that the Binding has not taken place yet. However since you are changing the reference via a command execute which happens after the binding you need to tell view that it changed
You need to make your poco class within the ObservableCollection implement INotifyPropertyChanged.
Example:
<viewModels:LocationsViewModel x:Key="viewModel" />
.
.
.
<ListView
DataContext="{StaticResource viewModel}"
ItemsSource="{Binding Locations}"
IsItemClickEnabled="True"
ItemClick="GroupSection_ItemClick"
ContinuumNavigationTransitionInfo.ExitElementContainer="True">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}" Margin="0,0,10,0" Style="{ThemeResource ListViewItemTextBlockStyle}" />
<TextBlock Text="{Binding Latitude, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Style="{ThemeResource ListViewItemTextBlockStyle}" Margin="0,0,5,0"/>
<TextBlock Text="{Binding Longitude, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Style="{ThemeResource ListViewItemTextBlockStyle}" Margin="5,0,0,0" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
public class LocationViewModel : BaseViewModel
{
ObservableCollection<Location> _locations = new ObservableCollection<Location>();
public ObservableCollection<Location> Locations
{
get
{
return _locations;
}
set
{
if (_locations != value)
{
_locations = value;
OnNotifyPropertyChanged();
}
}
}
}
public class Location : BaseViewModel
{
int _locationId = 0;
public int LocationId
{
get
{
return _locationId;
}
set
{
if (_locationId != value)
{
_locationId = value;
OnNotifyPropertyChanged();
}
}
}
string _name = null;
public string Name
{
get
{
return _name;
}
set
{
if (_name != value)
{
_name = value;
OnNotifyPropertyChanged();
}
}
}
float _latitude = 0;
public float Latitude
{
get
{
return _latitude;
}
set
{
if (_latitude != value)
{
_latitude = value;
OnNotifyPropertyChanged();
}
}
}
float _longitude = 0;
public float Longitude
{
get
{
return _longitude;
}
set
{
if (_longitude != value)
{
_longitude = value;
OnNotifyPropertyChanged();
}
}
}
}
public class BaseViewModel : INotifyPropertyChanged
{
#region Events
public event PropertyChangedEventHandler PropertyChanged;
#endregion
protected void OnNotifyPropertyChanged([CallerMemberName] string memberName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(memberName));
}
}
}
Your Subcategories property should be read-only.