wpf ListItem SelectedValue Object is always null - wpf

I have a simple ListBox and a TextBox as under.I want to display the selectedvalue property of Listbox in the textbox,but my ViewModel's selected object is always null.
What am i missing here?
My XAML
<StackPanel>
<Canvas>
<TextBox x:Name="TxtMail" Width="244" FontSize="14" Canvas.Left="36" Canvas.Top="34" Height="20" Text="{Binding CurrentRec.Name,Mode=OneWay}" />
<ListBox x:Name="AllMatching" Width="{Binding ElementName=TxtMail,Path=Width}" Height="100" Canvas.Top="54" Canvas.Left="36" DisplayMemberPath="Name" SelectedItem="{Binding CurrentRec,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" SelectedValue="Name" SelectedValuePath="Name" ScrollViewer.VerticalScrollBarVisibility="Auto" ScrollViewer.HorizontalScrollBarVisibility="Auto" />
<Button Content="Test" x:Name="cmdtest" Click="cmdtest_Click"/>
</Canvas>
My ViewModel:
public class VM_Data : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public int p_ID;
public double p_SP, p_CP;
public string p_Name;
public List<DM_Data> AllData;
public DM_Data CurrentRec;
public VM_Data()
{
LoadData();
}
public int ID
{
get { return p_ID; }
set
{
if (p_ID != value)
{
RaisePropertyChangedEvent("ID");
p_ID = value;
}
}
}
public double SP
{
get { return p_SP; }
set
{
if (p_SP != value)
{
RaisePropertyChangedEvent("SP");
p_SP = value;
}
}
}
public double CP
{
get { return p_CP; }
set
{
if (p_CP != value)
{
RaisePropertyChangedEvent("CP");
p_CP = value;
}
}
}
public string Name
{
get { return p_Name; }
set
{
if (p_Name != value)
{
RaisePropertyChangedEvent("Name");
p_Name = value;
}
}
}
private void LoadData()
{
AllData = new List<DM_Data>();
string[] strNames = "Jatinder;Shashvat;shashikala;shamsher;shahid;justin;jatin;jolly;ajay;ahan;vijay;suresh;namita;nisha;negar;zenith;zan;zen;zutshi;harish;hercules;harman;ramesh;shashank;mandeep;aman;amandeep;amarjit;asim;akshay;amol;ritesh;ritivik;riz;samana;samaira;bhagwandass;bhagwan;bhawna;bhavna".Split(';');
for(int i=0;i<=strNames.GetUpperBound(0);i++)
{
DM_Data NewRec = new DM_Data();
NewRec.CP = new Random().Next(200, 400);
NewRec.SP = new Random().Next(1, 10);
NewRec.ID = i + 1;
NewRec.Name = strNames[i];
AllData.Add(NewRec);
}
AllData = AllData.OrderBy(item => item.Name).ToList();
}
private void RaisePropertyChangedEvent(string Property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(Property));
}
}
}
My DataModel
public class DM_Data
{
public int p_ID;
public double p_SP, p_CP;
public string p_Name;
public int ID
{
get { return p_ID; }
set { p_ID = value; }
}
public double SP
{
get { return p_SP; }
set { p_SP = value; }
}
public double CP
{
get { return p_CP; }
set { p_CP = value; }
}
public string Name
{
get { return p_Name; }
set { p_Name = value; }
}
MainWindow.Xaml.cs
public partial class MainWindow : Window
{
VM_Data ViewModel;
public MainWindow()
{
InitializeComponent();
ViewModel = new VM_Data();
this.DataContext = ViewModel;
AllMatching.ItemsSource = ViewModel.AllData;
}
private void cmdtest_Click(object sender, RoutedEventArgs e)
{
DM_Data crec = ViewModel.CurrentRec;
}
}

CurrentRec must be a property that raises the PropertyChanged event:
private DM_Data _currentRec;
public DM_Data CurrentRec
{
get { return _currentRec; }
set { _currentRec = value; RaisePropertyChangedEvent("CurrentRec"); }
}
In the code you have posted, it is a field and you cannot bind to fields:
public DM_Data CurrentRec;

You can't bind to fields! CurrentRec must be a property. At now it is a field.
Why do you set ItemsSource in code-behind? Set it in XAML.
You should call RaisePropertyChangedEvent after you've changed backing field, not before.
It is not right pattern for events raising: if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(Property)); } You need to save event delegate to variable first or use ?.Invoke.
Don't create new instances of Random on every iteration of loop because you will get equal values. Create the only one outside of the loop and use it.

What you are doing is kind of MVVM, but not really.
Here is a quick fix anyway:
Please take a look at the Bindings.
<StackPanel>
<Canvas>
<TextBox x:Name="TxtMail" Width="244" FontSize="14" Canvas.Left="36" Canvas.Top="34" Height="20" Text="{Binding ElementName=AllMatching, Path=SelectedItem.Name}" />
<ListBox x:Name="AllMatching"
Width="{Binding ElementName=TxtMail,Path=Width}"
Height="100"
Canvas.Top="54"
Canvas.Left="36"
DisplayMemberPath="Name"
SelectedItem="{Binding CurrentRec,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
ScrollViewer.VerticalScrollBarVisibility="Auto"
ScrollViewer.HorizontalScrollBarVisibility="Auto" />
<Button Content="Test" x:Name="cmdtest" Click="cmdtest_Click"/>
</Canvas>
</StackPanel>
I think you get the idea at: Text="{Binding ElementName=AllMatching, Path=SelectedItem.Name}".
Aditional Information
First:
You fire to early dude. Please first assign the value and then say its changed.
if (p_Name != value)
{
RaisePropertyChangedEvent("Name");
p_Name = value;
}
Second:
Use a ObservableCollection<DM_Data> to let your ListBox know about changes.
Third:
Use the posibility of Binding
Remove AllMatching.ItemsSource = ViewModel.AllData; and go like
<ListBox x:Name="AllMatching"
ItemsSource="{Binding Path=AllData}"
...
/>
And after all of this - please man check out some tutorials. And also refactor your code from VM_Data to DataViewModel thank you sir.

Related

WPF Update count of item when button is pushed

new to WPF and programming here I am trying to update an item in a ListView when a button is pushed if the item already exists in that ListView, for example a user inputs CAR and CAR is already in the ListView the CAR count should go from 1 to 2.
This is my InventoryItem class:
public class InventoryItem
{
public string Name { get; set; }
public int Count { get; set; }
}
Here is my ViewModel
public class ViewModel : ViewModelBase
{
private InventoryItem _item;
private int _count;
private ObservableCollection<InventoryItem> _inventoryItems;
private ICommand _addItem;
public InventoryItem Item
{
get
{
return _item;
}
set
{
_item = value;
NotifyPropertyChanged("Item");
}
}
public int Count
{
get { return _count; }
set { _count = value; NotifyPropertyChanged("Count"); }
}
public ObservableCollection<InventoryItem> InventoryItems
{
get
{
return _inventoryItems;
}
set
{
_inventoryItems = value;
NotifyPropertyChanged("Items");
}
}
public ICommand AddItem
{
get
{
if (_addItem == null)
{
_addItem = new RelayCommand(ParamArrayAttribute => this.Submit(), null);
}
return _addItem;
}
}
public ViewModel()
{
Item = new InventoryItem();
InventoryItems = new ObservableCollection<InventoryItem>();
InventoryItems.CollectionChanged += new NotifyCollectionChangedEventHandler(InventoryItems_CollectionChanged);
}
void InventoryItems_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
NotifyPropertyChanged("Items");
NotifyPropertyChanged("Count");
}
private void Submit()
{
if (InventoryItems.Any(p => p.Name == Item.Name))
{
InventoryItems.First(x => x.Name == Item.Name).ItemCount++;
}
else
{
InventoryItems.Add(Item);
}
}
}
Here is my View
<ListView x:Name="listBox" ItemsSource="{Binding InventoryItems}" Grid.Row="0" HorizontalAlignment="Stretch" Height="Auto" Margin="10,10,10,60" VerticalAlignment="Stretch">
<ListView.Resources>
<Style TargetType="GridViewColumnHeader">
<Setter Property="Visibility" Value="Collapsed"/>
</Style>
</ListView.Resources>
<ListView.View>
<GridView>
<GridViewColumn DisplayMemberBinding="{Binding Name}" Width="Auto"/>
<GridViewColumn DisplayMemberBinding="{Binding ItemCount}" Width="Auto"/>
</GridView>
</ListView.View>
</ListView>
Whenever an item that exists in the list is typed in it appears that the InventoryItems ObservableCollection is being updated however InventoryItems_CollectionChanged event is not being fired so the ListView is not being updated. Isn't the collection changing so that event should be fired to update the ListView or am I not understanding the Binding and the event?
You need to notify about property changes in the InventoryItem class to update the changes of ItemCount in the ListView.
Quick solution:
public class InventoryItem : ViewModelBase
{
public string Name
{
get { return _name; }
set
{
if (_name != value)
{
_name = value;
NotifyPropertyChanged(nameof(Name));
}
}
}
private string _name;
public int ItemCount
{
get { return _itemCount; }
set { _itemCount = value; NotifyPropertyChanged(nameof(ItemCount));
}
}
private int _itemCount;
}
}
The ObservableCollection class already contains handling of INotifyCollectionChanged.
You only need this line for the ObservableCollection. You can remove everything else that has to do with "InventoryItems" and the collection in your ViewModel.
public ObservableCollection<InventoryItem> InventoryItems { get; } = new ObservableCollection<InventoryItem>();
Also: When you add an item to the collection you need to create a new item. Otherwise you are adding the same object, that will not work.
This is my reduced ViewModel to how I think you want it to work:
public class ViewModel : ViewModelBase
{
private ICommand _addItem;
public string InputName
{
get { return _inputName; }
set
{
if (_inputName != value)
{
_inputName = value;
NotifyPropertyChanged(nameof(InputName));
}
}
}
private string _inputName;
public ObservableCollection<InventoryItem> InventoryItems { get; } = new ObservableCollection<InventoryItem>();
public ICommand AddItem
{
get
{
if (_addItem == null)
{
_addItem = new RelayCommand(ParamArrayAttribute => this.Submit(), null);
}
return _addItem;
}
}
private void Submit()
{
if (InventoryItems.Any(p => p.Name == InputName))
{
InventoryItems.First(x => x.Name == InputName).ItemCount++;
}
else
{
InventoryItems.Add(new InventoryItem() { Name = InputName, ItemCount = 1 });
}
}
}
To complete the picture, I have added following XAML for test:
<TextBox Text="{Binding InputName}" MinWidth="100" Margin="5"/>
<Button Content="Add" Command="{Binding AddItem}" Margin="5"/>

DataGrid is not binding in WPF

I am trying to bind DataGrid using MVVM approach in WPF, model is getting values but nothing is showing in DataGrid
Following is my code
public class TalleyEditorGrid : INotifyPropertyChanged
{
#region Properties
private string _Quantity;
private string _Ft;
private string _Inch;
private string _Comment;
public string Quantity { get { return _Quantity; } set { _Quantity = value; NotifyPropertyChanged("Quantity"); } }
public string Ft { get { return _Ft; } set { _Ft = value; NotifyPropertyChanged("Ft"); } }
public string Inch { get { return _Inch; } set { _Inch = value; NotifyPropertyChanged("Inch"); } }
public string Comment { get { return _Comment; } set { _Comment = value; NotifyPropertyChanged("Comment"); } }
#endregion
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(string propName) { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName)); }
}
In my xaml.cs
private ObservableCollection<TalleyEditorGrid> _TalleyEditorGrid = new ObservableCollection<TalleyEditorGrid>();
public ObservableCollection<TalleyEditorGrid> TalleyEditorCol
{
get { return _TalleyEditorGrid; }
}
On button click I am filling this collection
_TalleyEditorGrid.Add(new TalleyEditorGrid() { Quantity = Q, Ft = FT, Inch = In, Comment = Comment});
Xaml as follows
<DataGrid x:Name="TalleyEditor" ItemsSource="{Binding Path=TalleyEditorCol}" AutoGenerateColumns="True" Visibility="Collapsed"
CanUserAddRows="False"
HorizontalGridLinesBrush="{x:Null}"
VerticalGridLinesBrush="Silver"
Background="White"
HorizontalScrollBarVisibility="Hidden"
VerticalScrollBarVisibility="Hidden"
SelectionMode="Single"
SelectionUnit="FullRow"
CanUserReorderColumns="True"
CanUserSortColumns="True" DataGridCell.GotFocus="TalleyEditor_GotFocus"
RowHeaderWidth="0" HorizontalAlignment="Left" VerticalAlignment="Top" RowHeight="17" ColumnHeaderHeight="21" PreviewKeyDown="TalleyEditor_PreviewKeyDown" LostFocus="TalleyEditor_LostFocus" CellEditEnding="myDG_CellEditEnding">
Set the DataContext of the window to itself:
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
Or set the DataContext of the DataGrid:
public MainWindow()
{
InitializeComponent();
TalleyEditor.DataContext = this;
}
If you put the DataGrid inside another DataGrid, you need to use a {RelativeSource} to be able to bind to a property of the parent window:
<DataGrid ... ItemsSource="{Binding Path=TalleyEditorCol, RelativeSource={RelativeSource AncestorType=Window}}">
</DataGrid>

Combobox data binding with item templates

I am trying to create a wpf combobox containing a list of World of warcraft items. I am using a item template for the combo box so that the items icon and item name are shown in the combobox drop down list. It works as is and I can start typing a item name and the list of items in the popup are automatically filtered.
The problem is that when I click an item I want the item name to be shown in the comboboxes text area. Instead what I get is a very brief ItemDisplayModel.ToString() then a empty string.
The ItemDisplayModel.ToString() being the ItemDisplayModel type that I selected from the list. Which makes sense cause the combobox control ItemsSource property contains an array of ItemDisplayModel types.
But in my AuctionHouseFilterItemNameModel.Value property I am detecting weather the value has changed and if so rebuild the list of items to be displayed in the combobox. So because the Text in the combobox was changed to ItemDisplayModel.ToString() when I click an item in the popup list it again rebuilds the list of items only this time there is no match because ItemDisplayModel.ToString() does not match any known item names.
All I am trying to do is when I click an item in the popup list I want the ItemDisplayModel.Name to be mapped to the AuctionHouseFilterItemNameModel.Value property and have the combobox text area to display AuctionHouseFilterItemNameModel.Value as well.
Does that make sense? I've tried numerous different ways and I am at a loss. Looking around the web did'nt give me the answer either. I'm sure it's something simple to fix but the solution eludes me.
Here is my XAML for the control
<UserControl
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"
xmlns:AuctionHouseSearchFilters="clr-namespace:Codefarts.WowTracks.DataMinerWPF.Models.AuctionHouseSearchFilters"
xmlns:Models="clr-namespace:Codefarts.WowTracks.DataMinerAppCore.Models;assembly=Codefarts.WowTracks.DataMinerAppCore"
xmlns:DataMinerAppCore="clr-namespace:Codefarts.WowTracks.DataMinerAppCore;assembly=Codefarts.WowTracks.DataMinerAppCore"
xmlns:dataMinerWpf="clr-namespace:Codefarts.WowTracks.DataMinerWPF"
x:Name="userControl"
x:Class="Codefarts.WowTracks.DataMinerWPF.Controls.AuctionHouseSearchFilters.AuctionHouseItemNameControl"
mc:Ignorable="d"
d:DesignHeight="51" d:DesignWidth="283">
<UserControl.Resources>
<dataMinerWpf:UriToBitmapImageConverter x:Key="UriToImageConverter" />
<BitmapImage x:Key='defaultImage' UriSource='/Resources\118.png' />
<DataTemplate x:Key="ItemTemplate" DataType="Models:ItemDisplayModel" >
<StackPanel Orientation="Horizontal" Margin="0 5 0 5">
<Image Width="50" Height="50" Stretch="Fill" Source="{Binding IconUrl, Converter={StaticResource UriToImageConverter}, TargetNullValue={StaticResource defaultImage}}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
<Label Content="{Binding Name}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</StackPanel>
</DataTemplate>
</UserControl.Resources>
<UserControl.DataContext>
<AuctionHouseSearchFilters:AuctionHouseFilterItemNameModel/>
</UserControl.DataContext>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="20"/>
</Grid.RowDefinitions>
<ComboBox x:Name="ItemList" MaxDropDownHeight="592" Grid.Row="0" ItemsSource="{Binding ItemDisplayModels}" ItemTemplate="{StaticResource ItemTemplate}" IsEditable="True" IsTextSearchEnabled="True" IsTextSearchCaseSensitive="False" Text="{Binding Value}" >
</ComboBox>
</Grid>
</UserControl>
Here is my code behind
public partial class AuctionHouseItemNameControl : UserControl, IAuctionHouseFilterControl
{
private Application app;
public AuctionHouseItemNameControl()
{
InitializeComponent();
}
public void SetModel(IAuctionHouseSearchFilter model)
{
this.DataContext = model;
}
public void SetApplication(Application app)
{
this.app = app;
}
private void ItemList_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
//if (model.Handled)
//{
// return;
//}
// model.Handled = true;
if (e.AddedItems != null && e.AddedItems.Count > 0)
{
var model = this.DataContext as Models.AuctionHouseSearchFilters.AuctionHouseFilterItemNameModel;
var item = e.AddedItems[0] as ItemDisplayModel;
// this.ItemList.SelectedValue = item.Name;
model.Value = item.Name;
// this.ItemList.SelectedItem = item.Name;
}
// model.Handled = false;
}
}
and here is my data models
[Export(typeof(IAuctionHouseSearchFilter))]
public class AuctionHouseFilterItemNameModel : IAuctionHouseSearchFilter, INotifyPropertyChanged
{
private string value;
private bool connected;
private Application app;
private ItemDisplayModel[] displayItems;
private CancellationTokenSource backgroundCancel;
private bool buildingDisplayItems;
private readonly object lockObject = new object();
private ItemDisplayModel displayValue;
// private bool Handled { get; set; }
public ItemDisplayModel DisplayValue
{
get
{
return this.displayValue;
}
set
{
if (value == null)
{
return;
}
this.Value = value.Name;
this.displayValue = value;
this.OnPropertyChanged();
}
}
public string Value
{
get
{
return this.value;
}
set
{
//if (this.Handled)
//{
// return;
//}
if (value == this.value)
{
return;
}
this.value = value;
// this.Handled = true;
this.OnPropertyChanged();
var cancellationTokenSource = this.backgroundCancel;
if (cancellationTokenSource != null)
{
cancellationTokenSource.Cancel();
}
this.BuildDisplayItems();
// this.Handled = false;
}
}
public IEnumerable<AuctionDataModel> Filter(MainFilterModel model, IEnumerable<AuctionDataModel> items)
{
if (!this.connected)
{
return items;
}
// get item id from it's name
var list = this.app.ItemNames[model.SelectedRegion];
var id = list.FirstOrDefault(x => x.Name.ToLowerInvariant().Contains(this.value.Trim().ToLowerInvariant()));
return items.Where(x => id != null && x.ItemId == id.Id);
}
public IEnumerable<ItemDisplayModel> ItemDisplayModels
{
get
{
return this.displayItems;
}
}
public async void BuildDisplayItems()
{
if (this.buildingDisplayItems)
{
return;
}
if (!this.connected)
{
this.displayItems = null;
}
// return this.GetDisplayItems();
this.buildingDisplayItems = true;
this.backgroundCancel = new CancellationTokenSource();
this.OnPropertyChanged("ItemDisplayModels");
await Task.Factory.StartNew(
() =>
{
var originalItems = this.displayItems;
this.displayItems = new[] { new ItemDisplayModel() { Name = "Rebuilding list..." } };
var correctedSearchValue = this.value.Trim().ToLowerInvariant();
//lock (this.lockObject)
//{
this.displayItems = (string.IsNullOrWhiteSpace(this.value) ?
this.app.DisplayItemModels :
this.app.DisplayItemModels.Where(x => x.Name.ToLowerInvariant().Contains(correctedSearchValue))).Take(100).AsParallel().ToArray();
this.buildingDisplayItems = false;
this.OnPropertyChanged("ItemDisplayModels");
},
this.backgroundCancel.Token);
}
public string Name
{
get
{
return "Item Name";
}
}
public Type Control
{
get
{
return typeof(AuctionHouseItemNameControl);
}
}
public virtual IAuctionHouseSearchFilter Clone()
{
return new AuctionHouseFilterItemNameModel()
{
Value = this.Value
};
}
public void Connect(Application app)
{
if (this.connected)
{
return;
}
this.app = app;
this.connected = true;
}
public void Disconnect()
{
if (!this.connected)
{
return;
}
this.app = null;
this.connected = false;
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public class ItemDisplayModel : INotifyPropertyChanged
{
private string iconUrl;
private string region;
private string name;
private int itemId;
public int ItemId
{
get
{
return this.itemId;
}
set
{
if (value == this.itemId)
{
return;
}
this.itemId = value;
this.OnPropertyChanged();
}
}
public string Name
{
get
{
return this.name;
}
set
{
if (value == this.name)
{
return;
}
this.name = value;
this.OnPropertyChanged();
}
}
public string Region
{
get
{
return this.region;
}
set
{
if (value == this.region)
{
return;
}
this.region = value;
this.OnPropertyChanged();
}
}
public string IconUrl
{
get
{
return this.iconUrl;
}
set
{
if (value == this.iconUrl)
{
return;
}
this.iconUrl = value;
this.OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
The problem is that when I click an item I want the item name to be shown in the comboboxes text area. Instead what I get is a very brief ItemDisplayModel.ToString() then a empty string.
To get the Name property displayed in the editable text area of the ComboBox use TextSearch.TextPath so your ComboBox definition would look like:
<ComboBox x:Name="ItemList"
Grid.Row="0"
IsEditable="True"
IsTextSearchCaseSensitive="False"
IsTextSearchEnabled="True"
ItemTemplate="{StaticResource ItemTemplate}"
ItemsSource="{Binding ItemDisplayModels}"
MaxDropDownHeight="592"
TextSearch.TextPath="Name" />
Now when an item is selected from the dropdown instead of seeing ItemDisplayModel.ToString(), you will see the Name property.

Wpf binding is not working properly

My ViewModel
public class MyViewModel : ViewModelBase
{
// INotifyPropertyChanged is implemented in ViewModelBase
private String _propX;
public String PropX
{
get { return _propX; }
set
{
if (_propX != value)
{
_propX = value;
RaisePropertyChanged(() => PropX);
}
}
}
private String _propY;
public String ServerIP
{
get { return _propY; }
set
{
if (_propY != value)
{
_propY = value;
RaisePropertyChanged(() => ServerIP);
}
}
}
public A()
{
this._propY = "000.000.000.000";
this._propY = "000.000.000.000";
}
}
// EDIT
// This is the command that resets the properties
private RelayCommand _resetFormCommand;
public ICommand ResetConnectionFormCommand
{
get
{
if (_resetFormCommand == null)
{
_resetFormCommand = new RelayCommand(param => this.ExecuteResetFormCommand(), param => this.CanExecuteResetFormCommand);
}
return _resetFormCommand;
}
}
private bool CanExecuteResetFormCommand
{
get
{
return !String.IsNullOrWhiteSpace(this._propX) ||
!String.IsNullOrWhiteSpace(this._propY);
}
}
private void ExecuteResetFormCommand()
{
this._propX = "";
this._propY = "";
}
My View xaml
<TextBox Name="propX" Text="{Binding PropX }" PreviewTextInput="textBox_PreviewTextInput" />
<TextBox Name="propY" Text="{Binding PropY }" PreviewTextInput="textBox_PreviewTextInput" />
<Border>
<Button Content="Reset" Name="resetBtn" Command="{Binding ResetFormCommand}" />
</Border>
My View code behind
private MyViewModel vm;
public ConnectionUserControl()
{
InitializeComponent();
vm = new MyViewModel();
this.DataContext = vm;
}
private void textBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
ValidateInput(sender as TextBox, e);
}
The reset command resets the properties in my view model but the textboxes still contain their values, the binding is not working properly :(
Am i missing something here?
You should reset the properties, not the private members:
private void ExecuteResetFormCommand()
{
this.PropX = "";
this.PropY = "";
}
How are you resetting the values? You may be overriding the databinding when you reset the values. It would be helpful if you post the code that gets executed when the button is clicked.
In your xaml-code you have to set the binding like:
<TextBox Name="propX" Text="{Binding PropX, Mode=TwoWay}" .../>
binding has to be two way in order for textbox to update itself from viewmodel
In your Code-behind, you have a property ServerIP, which I think you wanted to be named as PropY, since your TextBox binds to a PropY property.
<TextBox Name="propY" Text="{Binding PropY }" PreviewTextInput="textBox_PreviewTextInput" /
Also, you should be assigning the value to your property in your ExecuteResetFormCommand command, and not your private member since the private member does not trigger INotifyPropertyChanged
private void ExecuteResetFormCommand()
{
this.PropX = "";
this.PropY = ""; // <-- Currently you have PropY declared as ServerIP
}

ObservableCollection

Ive posted another thread regarding refreshing a silverlight listbox - In the meantime Ive become slightly more familiar with the issue. It has to do with implementing the ObservableCollection interface.
Im using RIA services to populate a listbox with a collection of type ObservableCollection. The problem is refreshing the Items once the database has been updated. I am using a silverlight child window to save the data to the database, and this is happening correctly On the close event of the child window.
Can anyone give me more information as to why the ListBox is not updating.
Thanks
You need to make your poco class that is used within your ObservableCollection implement INotifyChanged.
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));
}
}
}

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