WPF：如何从 TextBox 获取当前绝对行号和列号（忽略文本换行）

Question

I am trying to get the absolute position of the line and column/character of caret in TextBox (like it implemented in Windows notepad). I know about TextBox.GetLineIndexFromCharacterIndex() or TextBox.GetCharacterIndexFromLineIndex() , but those methods returns relative postion (I mean that this methods counts wrapped lines) and for example if first line wraps to second line, this method will return index of second line, so I need another solution for this. Also I tried calculate position by myself (using loop through the string) but with large amount of text it works very slowly.

Text without wrapping Text with wrapping

Answer 1

I don't think there's any way you'll be able to get the line number of a given offset (character) without looping through the text in some way. However, some methods will be more efficient than others.

You can take some inspiration from the TextBox control itself, since the source code is freely available here:
https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/windows/Controls/TextBox.cs

The TextBox needs to enumerate over every character anyway in order to display the text. As part of that process it also needs to decide when to start new lines. To make future calculations faster, it keeps an internal list of "line metrics"- basically a list of where each line starts and how long each line is. It uses this internal list to do calculations like GetCharacterIndexFromLineIndex and GetLineIndexFromCharacterIndex more efficiently, without having to go through each character again.

You should be able to do something similar. Make your own list of line positions at the start by looping through the text in the background when it's first loaded, then keep that list up to date as changes are made.