Copy String of a ListViewItem into a TextBox

Question

So I'm working on a calculator, basically a copy of the Windows Version, as a training excercise. I have implemented a History of past calculations, and I was asked to transform this history from TextBox to Listview. What I want to do is copy one of the past calculations back into the Calculator TextBox when I click on it, just like in the Windows Calculator.

My ListViewCode:

<ListView Grid.Column="0" Grid.Row="1" Foreground="#616161" Name="history" Background="Transparent" 
          HorizontalAlignment="Stretch" BorderThickness="0" Margin="10,10,10,0">
    <ListView.ItemContainerStyle>
        <Style TargetType="ListViewItem">
            <EventSetter Event="MouseLeftButtonDown" Handler="RetrievePastCalculation" />
        </Style>
    </ListView.ItemContainerStyle>
</ListView>

And this is the RetrievePastCalculation method, but it doesn't work, nothing happens when I click on a ListViewItem. I'm new to WPF by the way.

private void RetrievePastCalculation(object sender, MouseButtonEventArgs e)
{
    innerTextBox.Text = history.SelectedItems.ToString();
}

This is where I add items to the ListView I think, it's the Equal button method:

private void ButtonEquals_Click(object sender, RoutedEventArgs e)
{
    Calculator calculate = new Calculator();
    textBox.Text = calculate.Calculate(innerTextBox.Text);

    history.Items.Add(innerTextBox.Text + "=" + textBox.Text);

    innerTextBox.Clear();
}

Answer 1

history.SelectedItems is a collection, so calling ToString on it won't give you anything other than the name of the type. If you try it in the debugger (which you should), you'll see that it returns System.Windows.Controls.SelectedItemCollection. Now, at this point you can either fix your issue one of two ways: you can continue to use your current event-based approach, or you can use binding.

Events

With events, you can hook a handler to the Selected event for each ListItem that you add to the list:

private void ButtonEquals_Click(object sender, RoutedEventArgs e)
{
    Calculator calculate = new Calculator();
    textBox.Text = calculate.Calculate(innerTextBox.Text);

    var item = new ListViewItem();
    item.Content = innerTextBox.Text + "=" + textBox.Text;
    item.Selected += HistoryItem_Selected //hooks the handler to the 'Selected' event
    history.Items.Add(item);

    innerTextBox.Clear();
}

then define the handler itself:

private void HistoryItem_Selected(object sender, RoutedEventArgs e)
{
   // here 'sender' will be the ListItem which you clicked on
   // but since it's an object we need to cast it first
   ListViewItem listItem = (ListViewItem)sender;

   // now all that's left is getting the text and assigning it to the textbox
   innerTextBox.Text = listItem.Content.ToString();
}

Binding

Binding is much simpler as far as the amount of code is concerned, but has a steeper learning curve. Here, instead of setting the TextBox.Text property directly, we will specify a binding expression. This means that the value will always be the same as that of the bound expression.

<Window x:Class="WpfApplication1.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>
            <ListView Grid.Column="0" Grid.Row="0" Name="history" />
            <TextBox Text="{Binding ElementName=history, Path=SelectedItem.Content}" />
            <Button Name="ButtonEquals" Content="equals" Click="ButtonEquals_Click"/>
        </StackPanel>
    </Grid>
</Window>

I've run this in a new WPF project and it works as expected: the text box displays whatever text is in the clicked item from the list.

One thing to note is that both solutions assume that you are assigning strings to the ListViewItem Content. As you may know, you can assign other controls or any object to the Content property of a UI Control (ListViewItem inherits from Control). That's why the ListViewItem.Add method takes an argument of type object and is not restricted to one of type string. If you assigned anything other than a string in your button click event handler, both of the two cases above would likely break.