The idea is to find the offset of the first character (IndexOf
) and then to find the TextPointer at this index (but by counting only text characters).
public TextRange FindTextInRange(TextRange searchRange, string searchText)
{
int offset = searchRange.Text.IndexOf(searchText, StringComparison.OrdinalIgnoreCase);
if (offset < 0)
return null; // Not found
var start = GetTextPositionAtOffset(searchRange.Start, offset);
TextRange result = new TextRange(start, GetTextPositionAtOffset(start, searchText.Length));
return result;
}
TextPointer GetTextPositionAtOffset(TextPointer position, int characterCount)
{
while (position != null)
{
if (position.GetPointerContext(LogicalDirection.Forward) == TextPointerContext.Text)
{
int count = position.GetTextRunLength(LogicalDirection.Forward);
if (characterCount <= count)
{
return position.GetPositionAtOffset(characterCount);
}
characterCount -= count;
}
TextPointer nextContextPosition = position.GetNextContextPosition(LogicalDirection.Forward);
if (nextContextPosition == null)
return position;
position = nextContextPosition;
}
return position;
}
This is how to use the code:
TextRange searchRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
TextRange foundRange = FindTextInRange(searchRange, "expert");
foundRange.ApplyPropertyValue(TextElement.ForegroundProperty, new SolidColorBrush(Colors.Red));