WPF Richtextbox文字标记

1.利用正则获取文字位置

 1 TextRange t=new TextRange(MyRichTextBox.Document.ContentStart,MyRichTextBox.Document.ContentEnd);
 2 var strR=new StringBuilder();
 3 for (int i = 0; i < strKeyWord.Length; i++)//strKeyword为要查找的关键字
 4 {
 5 strR.Append("[");
 6 strR.Append(strKeyWord[i]);
 7 strR.Append("]");
 8 }
 9 Regex regex = new Regex(strR.ToString());
10 var matchs = regex.Matches(t.Text);

2.解析正则表达式结果并标记文字

1 foreach (Match match1 in match)
2 {
3         TextRange tr = new TextRange(GetTextPointerAtOffset(MainRichTextBox,match1.Index), GetTextPointerAtOffset(MainRichTextBox,match1.Index+match1.Length));
4          tr.ApplyPropertyValue(TextElement.ForegroundProperty, Brushes.Red);//设置关键字颜色
5          tr.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Bold);//设置关键字加粗
6 }

3.GetTextPointerAtOffset函数（本函数转自https://answer-id.com/51419225）

 1 /// The rich text box.
 2 /// The offset.
 3 /// The TextPointer at the given character offset
 4 public  TextPointer GetTextPointerAtOffset( RichTextBox richTextBox, int offset)
 5         {
 6             var navigator = richTextBox.Document.ContentStart;
 7             int cnt = 0;
 8 
 9             while (navigator.CompareTo(richTextBox.Document.ContentEnd) < 0)
10             {
11                 switch (navigator.GetPointerContext(LogicalDirection.Forward))
12                 {
13                     case TextPointerContext.ElementStart:
14                         break;
15                     case TextPointerContext.ElementEnd:
16                         if (navigator.GetAdjacentElement(LogicalDirection.Forward) is Paragraph)
17                             cnt += 2;
18                         break;
19                     case TextPointerContext.EmbeddedElement:
20                         //TODO: Find out what to do here?
21                         cnt++;
22                         break;
23                     case TextPointerContext.Text:
24                         int runLength = navigator.GetTextRunLength(LogicalDirection.Forward);
25 
26                         if (runLength > 0 && runLength + cnt < offset)
27                         {
28                             cnt += runLength;
29                             navigator = navigator.GetPositionAtOffset(runLength);
30                             if (cnt > offset)
31                                 break;
32                             continue;
33                         }
34                         cnt++;
35                         break;
36                 }
37 
38                 if (cnt > offset)
39                     break;
40 
41                 navigator = navigator.GetPositionAtOffset(1, LogicalDirection.Forward);
42 
43             }//End while.
44 
45             return navigator;
46         }