Listbox problem when binding to a observableCollection

Question

Hello everyone. I was binding an observable collection to a listbox with no problem, everything was displaying fine.But then i realized that i had forgotten to implement the iNotifyPropertyChanged for the class that my observablecollection holds. i did this because i wanted the changes made to the collection to reflect back on the listbox. So i implemented this and behold the listbox stopped displaying data. Can anyone point out whats wrong i dont understand what im doing incorrectly. Thanks in advance to everyone.

 

The XAML

---------------------------------------------------------------------------------------------

<ListBox  Height="200" x:Name="testList" ScrollViewer.HorizontalScrollBarVisibility="Disabled" >
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <WrapPanel  />
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <Border Width="75" BorderBrush="Black" Margin="5" BorderThickness="1">
                       <StackPanel>
                            <TextBox Margin="1" BorderThickness="0.5" BorderBrush="Red" Height="22"  Text="{Binding Path= FirstName}" />
                            <TextBox Margin="1" BorderThickness="0.5" BorderBrush="Red" Height="22"  Text="{Binding Path= LastName}" />
                            <TextBox Margin="1" BorderThickness="0.5" BorderBrush="Red" Height="22"  Text="{Binding Path= City}" />
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

 

THE CLASS that implements the iNotifyPropertyChanged interface

---------------------------------------------------------------------------------------------

public class Class1 :INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public Class1()
        {
        }

        string fname;
        public string FirstName
        {
            get
            {
                return fname;
            }
            set
            {
                fname = value;
                PropertyChanged(this, new PropertyChangedEventArgs("FirstName"));
            }
        }

        string lname;
        public string LastName
        {
            get
            {
                return lname;
            }
            set
            {
                lname = value;
               PropertyChanged(this, new PropertyChangedEventArgs("LastName"));
            }
        }

        string c;
        public string City
        {
            get
            {
                return c;
            }
            set
            {
                c = value;
               PropertyChanged(this, new PropertyChangedEventArgs("City"));
            }
        }     
    }

 

THis is how i give the itemsSource to the list

---------------------------------------------------------------------------------------------

 

ObservableCollection<Class1> lst = new ObservableCollection<Class1>();

//Some dummy data

 for (int i = 0; i <= 100; i++)
            {
                Class1 c = new Class1() { FirstName = "blah blah blah", LastName = "who knows", City = "Miami" };
                lst.Add(c);
            }

 

//bind

this.testList.ItemsSource = lst;

 

 

If i dont implement the InotifyPropertYChanged interface in Class1 everything works fine so im pretty sure the error is in class 1 but i dont know what i did wrong implementing the inotifypropertychanged interface.

 

Again thanks in advance

Answer 1

Hello

I think your implementation of InotifyPropertyChanged is wrong. Here i support u one very small class implemeting the interface.

 class DeliveryContent : INotifyPropertyChanged
  {
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(String info)
    {
      if (PropertyChanged != null)
      {
        PropertyChanged(this, new PropertyChangedEventArgs(info));
      }
    }

  

    private string barcode = "";
    public string Barcode
    {
      get
      {
        return barcode;
      }
      set
      {
        barcode = value;
        this.OnPropertyChanged("Barcode");
      }
    }
}

Hope that helps good luck with coding!

Dimitar.

Answer 2

Hello,

I think you should check for not null before call PropertyChanged:

 

 

   string c;
  public string City
  {
   get
   {
    return c;
   }
   set
   {
    c = value;
     if (PropertyChanged != null)
     PropertyChanged(this, new PropertyChangedEventArgs("City"));
   }
  } 

Good Luck

 

 

Answer 3

Hi guys thanks for the feedback, i tried what you guys suggested but still no luck.

Answer 4

Hey guys you where right my implementation was wrong. this fixed the problem...

 

public event PropertyChangedEventHandler PropertyChanged;
        private void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

 

then to notify the update do something like this

 

 NotifyPropertyChanged("FirstName");

 

basically what the first guy suggested.. thanks guys