RichTextBoxにバインド

転載元：http://stackoverflow.com/questions/6475775/how-do-i-bind-string-in-xaml-format-to-xaml-property-of-richtextbox-in-silverl

ほぼ元のままですがちょっとだけ変えました。XamlSource → InlinesXaml
自分で使うのに Section とか Paragraph を渡す必要がなかったので Inlines だけ渡すようにカスタマイズ。

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;

namespace test
{
    public static class RichTextBoxBinder
    {
        private const string _XAML_BEGIN = @"<Section xml:space=""preserve"" HasTrailingParagraphBreakOnPaste=""False"" xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation""><Paragraph>";
        private const string _XAML_END = @"</Paragraph></Section>";

        #region InlinesXaml ----------------------------------------------------

        #region RichTextBox attached properties

        public static readonly DependencyProperty InlinesXamlProperty =
          DependencyProperty.RegisterAttached(
            "InlinesXaml",
            typeof(string),
            typeof(RichTextBox),
            new PropertyMetadata(OnInlinesXamlPropertyChanged));

        private static void OnInlinesXamlPropertyChanged(
          DependencyObject d,
          DependencyPropertyChangedEventArgs e)
        {
            var rtb = d as RichTextBox;
            if (rtb == null) throw new ArgumentException(
              "Expected a dependency object of type RichTextBox.", "d");

            string xaml = null;
            if (e.NewValue != null)
            {
                xaml = e.NewValue as string;
                if (xaml == null) throw new ArgumentException("Expected a value of type string.", "e.NewValue");
            }

            // Set the xaml and reset selection 
            //rtb.Xaml = xaml ?? string.Empty;
            rtb.Xaml = (xaml == null) ? string.Empty : _XAML_BEGIN + xaml + _XAML_END;
            rtb.Selection.Select(rtb.ContentStart, rtb.ContentStart);
        }

        #endregion

        public static void SetInlinesXaml(this RichTextBox rtb, string xaml)
        {
            rtb.SetValue(InlinesXamlProperty, xaml);
        }

        public static string GetInlinesXaml(this RichTextBox rtb)
        {
            return (string)rtb.GetValue(InlinesXamlProperty);
        }

        #endregion InlinesXaml -------------------------------------------------
    } 

}

Xaml側

<RichTextBox local:RichTextBoxBinder.InlinesXaml="{Binding HogeXaml}" />

バインドされる側

public string HogeXaml
{
    get {
        var xaml = @"あいうえお<LineBreak />"
                 + @"<Span Foreground=""Red"">あいうえお</Span><LineBreak />"
                 + @"さしすせそ";
        return xaml;
    }
}