仅单向绑定到TextBox

Question

I need to bind a List<Key> to TextBox . I've written a converter which converts from List<Key> to string (the ConvertBack method just throws an exception - it isn't used). Problem is that when I try to use this converter, it shows me an error: The TypeConverter for "IValueConverter" does not support converting from a string. It appears that the problem is caused because it's trying to convert string from TextBox to List<Key>, but I don't want to do that (user won't "write" to this TextBox ). I've already thought about using something else than TextBox - perhaps TextBlock which I think would solve the problem, but I'd like to use TextBox for some other reasons.

My property I want to bind:

public partial class Settings : Window
{
    public List<Key> hotkeyCapture_keys { get; set; }
    ...

Converter:

class ListKeyToStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return string.Join(" + ", (List<Key>)value);
    }
    ...

And TextBox:

<TextBox ... Text="{Binding hotkeyCapture_keys, Converter=ListKeyToStringConverter}" />

When try to Build it, the app immediately shuts down with "XamlParseException occured" .

Can anyone tell me how to solve this problem?

Thanks

Answer 1

Not sure if this is really something you want to do. If you want a read-only TextBox there are other ways of doing so out there already; one that you mentioned, another being RichTextBox . But I'll assume you know what you want.

You'll first want to use this in your Convert (don't forget to add using System.Linq; ):

return string.Join(" + ", ((List<Key>)value).Select(x=> x.Name)); 
//where Name is a public property in type Key

Secondly--bingo, TextBox.Text binds Mode=TwoWay by default. You can change that to OneWay or OneTime :

<TextBox ... Text="{Binding hotkeyCapture_keys, Mode=OneTime, Converter=ListKeyToStringConverter}" />

Also, you're throwing an exception. Something has to handle that exception. Nothing is. Instead of throwing an exception in ConvertBack , just call return null;

Answer 2

change your return value in converter to

 return String.Join(" + ", ((List<Key>)value).ToArray());

you can have a look at WPF textblock binding with List<string>