Support background colour when syntax highlighting.

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs

@@ -154,6 +154,11 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 				if (b != null)
 					element.TextRunProperties.SetForegroundBrush(b);
 			}
+			if (color.Background != null) {
+				Brush b = color.Background.GetBrush(CurrentContext);
+				if (b != null)
+					element.TextRunProperties.SetBackgroundBrush(b);
+			}
 			if (color.FontStyle != null || color.FontWeight != null) {
 				Typeface tf = element.TextRunProperties.Typeface;
 				element.TextRunProperties.SetTypeface(new Typeface(

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/Resources/ASPX.xshd

@@ -4,7 +4,7 @@
 	<Color name="ASPSectionStartEndTags" foreground="Black" background="Yellow" exampleText="&lt;% System.Console.WriteLine(&quot;Hello World!&quot;); %&gt;" /> 
 	<Color name="ASPSection" foreground="Black" background="#FFF7F2E3" exampleText="&lt;% System.Console.WriteLine(&quot;Hello World!&quot;); %&gt;" />
 	<RuleSet ignoreCase="true">
-		<Span color="ASPSection" ruleSet="ASP" multiline="true">
+		<Span ruleSet="ASP" multiline="true">
 			<Begin color="ASPSectionStartEndTags">&lt;%</Begin>
 			<End color="ASPSectionStartEndTags">%&gt;</End>
 		</Span>