regexwpfrichtextboxtextrange

GetPositionAtOffset() don't return good position

I use a RichTextBox in WPF (4.0) and I use the GetPositionAtOffset() method to get a text range between two position in the content in RichTextBox.

1) I initialize the text pointer "position" from MyRichTextBox.Document.ContentStart :

TextPointer position = RTBEditor.Document.ContentStart;

2) I get the text from my RichTextBox like that :

var textRun = new TextRange(RTBEditor.Document.ContentStart, RTBEditor.Document.ContentEnd).Text;

3) With Regex I find a string that I want in textRun and get the begin's index and the end's index (I search a text between "/*" and "*/"):

Regex regex = new Regex(@"/\*([^\*/])*\*/");
var match = regex.Match(textRun);
TextPointer start = position.GetPositionAtOffset(matchBegin.Index, LogicalDirection.Forward);
TextPointer end = position.GetPositionAtOffset(matchBegin.Index + matchBegin.Length, LogicalDirection.Backward);

But, when I use these pointers in a textrange and colorize the text inside, it's not the good text matched in my regex (with goods indexes) which is colorized in my RichTextBox.

Why the GetPositionAtOffset() method don't give the position at the index specified ? It's this method the problem or it's somewhere else ?

Thank's for reply, I am stopped in my development.

Solution

  • According to this, https://msdn.microsoft.com/en-us/library/ms598662%28v=vs.110%29.aspx

    GetPositionAtOffset returns a TextPointer to the position indicated by the specified offset, in symbols, from the beginning of the current TextPointer.

    Any of the following is considered to be a symbol: