How binding data depending on the value? - xaml

Question

I have ObservableCollection and value that need to find the item in the collection. any ideas? (p.s converter not good idea, because i have many collections)

Answer 1

This functionality (applying a filter) belongs into the ViewModel. Here is an easy example for illustration.
You might also want to look at the CollectionViewSource for a more refined version of the same concept.
Xaml:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:ViewModel />
</Window.DataContext>
<StackPanel Orientation="Horizontal" VerticalAlignment="Top" >
<ListBox ItemsSource="{Binding MyClasses}" DisplayMemberPath="Name" Margin="5" />
<ListBox ItemsSource="{Binding MyFilteredClasses}" DisplayMemberPath="Name" Margin="5" />
<TextBox Text="{Binding MySelectedClass.Name}" Margin="5" />
</StackPanel>
</Window>
ViewModel:
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
namespace WpfApplication1
{
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
private ObservableCollection<Class1> _myClasses;
public ObservableCollection<Class1> MyClasses { get { return _myClasses; } set { _myClasses = value; OnPropertyChanged("MyClasses"); } }
private List<Class1> _myFilteredClasses;
public List<Class1> MyFilteredClasses { get { return _myFilteredClasses; } set { _myFilteredClasses = value; OnPropertyChanged("MyFilteredClasses"); } }
private Class1 _mySelectedClass;
public Class1 MySelectedClass { get { return _mySelectedClass; } set { _mySelectedClass = value; OnPropertyChanged("MySelectedClass"); } }
public ViewModel()
{
MyClasses = new ObservableCollection<Class1>()
{
new Class1() { Name = "Connelly" },
new Class1() { Name = "Donnelly" },
new Class1() { Name = "Fonnelly" },
new Class1() { Name = "McGregor" },
new Class1() { Name = "Griffiths" }
};
// filter your ObservableCollection by some criteria, and bind to the result (either another list, or just one item)
MyFilteredClasses = MyClasses.Where(c => c.Name.EndsWith("onnelly")).ToList();
MySelectedClass = MyClasses.FirstOrDefault(c => c.Name.StartsWith("Mc"));
}
}
public class Class1 : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
private string _name;
public string Name { get { return _name; } set { _name = value; OnPropertyChanged("Name"); } }
}
}