Howto bind TextBox control to a StringBuilder instance?

Question

I would like several textboxes to react to changes of an underlying string. So if I were to change the content of the string, all those textboxes would change their content too.

Now, I can't use the String type for that as it is immutable. So I went with StringBuilder. But the Text property of a TextBox object only takes String.

Is there an easy way to "bind" the StringBuilder object to the Text property of a TextBox?

Many thanks!

PS: The TextBox is currently WPF. But I might switch to Windows Forms because of Mono.

Answer 1

You could always expose a property that's getter returns the ToString() of the Stringbuilder. The form could then bind to this property.

private StringBuilder _myStringBuilder;

public string MyText
{
  get { return _myStringBuilder.ToString(); }
}

Answer 2

Here what I use to bind StringBuilder to TextBox in WPF:

public class BindableStringBuilder : INotifyPropertyChanged
{
    private readonly StringBuilder _builder = new StringBuilder();

    private EventHandler<EventArgs> TextChanged;

    public string Text
    {
        get { return _builder.ToString(); }
    }

    public int Count
    {
        get { return _builder.Length; }
    }

    public void Append(string text)
    {
        _builder.Append(text);
        if (TextChanged != null)
            TextChanged(this, null);
        RaisePropertyChanged(() => Text);
    }

    public void AppendLine(string text)
    {
        _builder.AppendLine(text);
        if (TextChanged != null)
            TextChanged(this, null);
        RaisePropertyChanged(() => Text);
    }

    public void Clear()
    {
        _builder.Clear();
        if (TextChanged != null)
            TextChanged(this, null);
        RaisePropertyChanged(() => Text);
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }

    public void RaisePropertyChanged<T>(Expression<Func<T>> propertyExpression)
    {
        if (propertyExpression == null)
        {
            return;
        }

        var handler = PropertyChanged;

        if (handler != null)
        {
            var body = propertyExpression.Body as MemberExpression;
            if (body != null)
                handler(this, new PropertyChangedEventArgs(body.Member.Name));
        }
    }

    #endregion


}

In ViewModel:

public BindableStringBuilder ErrorMessages { get; set; }
ErrorMessages.AppendLine("Missing Image: " + imagePath);

In Xaml:

<TextBox Text="{Binding ErrorMessages.Text, Mode=OneWay}"/>

Of course you can expose other StringBuilder methods if you need.