如何获取特定项目列表框 C# MVVM WPF

Question

Hi i try to get specific item from a listbox. I try to bind but i get crash. Using Prism framework how can i bind to get specific item from listbox, what template i need to make. This is test code:

<ListBox SelectedItem="{Binding SelectIndex}" HorizontalAlignment="Left" Height="297" Margin="57,41,0,0" VerticalAlignment="Top" Width="681">
                        <ListBoxItem>
                                <TextBlock Text="Test123"/>
                        </ListBoxItem>
                        <ListBoxItem>
                                <TextBlock Text="Test123"/>
                        </ListBoxItem>
                </ListBox>

C# code:

public int SelectIndex
                {
                        get
                        {
                                return 1;
                        }
                }

How can i get if i want specific item from this list? What variable type need to make for binding listbox to select items?

Answer 1

It's crashing because you are binding SelectedItem (of type object ) to your SelectIndex property ( int property) in your view model (VM). ListBox like many WPF controls have distinct SelectedIndex and SelectedItem properties for binding.

If you want to bind to an int property in order to get the index you should be binding the ListBox 's SelectedIndex property instead.

Change:

<ListBox SelectedItem="{Binding SelectIndex}" ...

...to:

<ListBox SelectedIndex="{Binding SelectIndex}" ...

Your VM remains as:

public int SelectIndex { get { return 1; } }

Though to be more useful and allow users to choose different items it should be:

public int SelectIndex { get; set; } // TODO: add support for INotifyPropertyChanged

Optionally you can add:

    <ListBox SelectedIndex="{Binding SelectIndex}" 
             SelectedItem="{Binding SelectedItem}" ...

ViewModel:

    public int SelectIndex { get; set; } // TODO: add support for INotifyPropertyChanged

    // replace object with your type
    public object SelectedItem { get; set; } // TODO: add support for INotifyPropertyChanged