Question

My code:
XAML:

<Window x:Class="BindingTut.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <StackPanel>
            <TextBox Text="{Binding FirstName}"/>
            <Button Content="Button" Height="23" Name="button1" Width="75" Click="button1_Click" />
        </StackPanel>
    </Grid>
</Window>

Customer class:

public class Customer
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

Code behind:

public partial class MainWindow : Window, INotifyPropertyChanged
{
    private int index = 0;
    public Customer Tmp;
    List<Customer> ar = new List<Customer>();

    public MainWindow()
    {
        InitializeComponent();
        ar.Add(new Customer { FirstName = "qwe", LastName = "rty" });
        ar.Add(new Customer { FirstName = "asd", LastName = "asd" });
        this.Tmp = ar[index];
        this.DataContext = this.Tmp;
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        this.Tmp = ar[++index];
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs("Tmp"));
        }

    }

    public event PropertyChangedEventHandler PropertyChanged;

}

So when application loads, everything is fine – textbox shows “qwe”, but button, which should load second customer object doesn’t work. What am I doing wrong?

Answer 1

You’re not changing the DataContext. You’re changing the value in the property that you set the DataContext to.

You don’t need a Tmp property at all. Just change the DataContext in your event handler, e.g.:

DataContext = ar[++index];