How Can Attached Properties Simplify WPF RichTextBox Data Binding?

Simplify WPF RichTextBox data binding with attached properties

Data binding of WPF RichTextBox has always been a challenge for developers. Two common approaches include subclassing RichTextBox and adding a DependencyProperty, or using a "proxy". However, both methods have drawbacks.

Simpler solution: additional DocumentXaml properties

To overcome these limitations, an easier way is to create an additional DocumentXaml property. This property allows you to bind the RichTextBox directly to the document.

Usage:

<code class="language-xml"><TextBox Text="{Binding FirstName}"></TextBox>
<TextBox Text="{Binding LastName}"></TextBox>
<RichTextBox local:RichTextBoxHelper.DocumentXaml="{Binding Autobiography}"></RichTextBox></code>

Implementation details:

The implementation process involves updating the document of the RichTextBox when the DocumentXaml property changes. The code is as follows:

<code class="language-csharp">public class RichTextBoxHelper : DependencyObject
{
    public static string GetDocumentXaml(DependencyObject obj)
    {
        return (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解析为文档并将其设置为RichTextBox
                    var doc = new FlowDocument();
                    var range = new TextRange(doc.ContentStart, doc.ContentEnd);
                    range.Load(new MemoryStream(Encoding.UTF8.GetBytes(GetDocumentXaml(richTextBox))), DataFormats.Xaml);
                    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>

Alternative format:

The same method can be used with TextFormats.RTF or TextFormats.XamlPackage. For XamlPackage, the type of DocumentXaml property will be byte[] instead of string.

Advantages of XamlPackage format:

XamlPackage has the advantages of embedded images and ease of use compared to pure XAML.

Conclusion:

This additional DocumentXaml property provides a simple and effective solution for data binding in RichTextBox, overcoming the limitations of other methods. It allows direct binding to documents and supports text formatting capabilities.

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