How Can I Simplify Data Binding for a WPF RichTextBox Document?

WPF RichTextBox document data binding simplified solution

When trying to implement data binding for a WPF RichTextBox document, there are two main solutions: create a custom RichTextBox derived class with dependent properties or use the "proxy" method. However, there is still room for improvement in these methods.

Simplified solution using attached attributes

A simpler alternative is to create an additional DocumentXaml attribute. This property allows easy binding of the RichTextBox to the document. How to use it is as follows:

<code class="language-xml"><textbox text="{Binding FirstName}"></textbox><textbox text="{Binding LastName}"></textbox><richtextbox local:richtextboxhelper.documentxaml="{Binding Autobiography}"></richtextbox></code>

Achievement

DocumentXamlThe implementation of attached properties revolves around loading XAML (or RTF) into a new FlowDocument when setting the property. Instead, when the FlowDocument changes, the property values ​​are updated.

The following code encapsulates the implementation:

<code class="language-csharp">public class RichTextBoxHelper : DependencyObject
{
    public static string GetDocumentXaml(DependencyObject obj) => (string)obj.GetValue(DocumentXamlProperty);
    public static void SetDocumentXaml(DependencyObject obj, string value) => obj.SetValue(DocumentXamlProperty, value);

    public static readonly DependencyProperty DocumentXamlProperty =
        DependencyProperty.RegisterAttached("DocumentXaml", typeof(string), typeof(RichTextBoxHelper), new FrameworkPropertyMetadata
        {
            BindsTwoWayByDefault = true,
            PropertyChangedCallback = (obj, e) =>
            {
                var richTextBox = (RichTextBox)obj;

                // 将XAML解析为文档
                var doc = new FlowDocument();
                var range = new TextRange(doc.ContentStart, doc.ContentEnd);
                range.Load(new MemoryStream(Encoding.UTF8.GetBytes(GetDocumentXaml(richTextBox))), DataFormats.Xaml);

                // 设置文档
                richTextBox.Document = doc;

                // 文档更改时更新源
                range.Changed += (obj2, e2) =>
                {
                    if (richTextBox.Document == doc)
                    {
                        MemoryStream buffer = new MemoryStream();
                        range.Save(buffer, DataFormats.Xaml);
                        SetDocumentXaml(richTextBox, Encoding.UTF8.GetString(buffer.ToArray()));
                    }
                };
            }
        });
}</code>

This method provides a convenient option for binding RichTextBox documents without the need for complex solutions or commercial controls.

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