my vs2008 addin for textformatting is awfully slow

Question

i wrote a little addin, which does some formatting of my C# code. in the addins Exec method i do the following

try {
    TextSelection selection = (EnvDTE.TextSelection)_applicationObject.ActiveDocument.Selection;
    String foo = String.Empty;                      
    if (!text.IsEmpty) {                            
    foo = someCoolObjectThatFormatsText.Format(selection.Text);
    selection.Text = foo;  // here everything gets painfully slow :-(
    }
}
catch (Exception) {
    throw;
}

when the line with the code "SelectedText.Text = foobar;" is call, VS rebuilds each line of the selection step by step. You can easily watch it doing this step. But i don't get, why it is that slow.

Any hints? TIA

Answer 1

JFTR: I had to use TextSelection.Insert(...), but to also get visual studios depth of indention, i also had to mess with the selected text to span the selection also over the full first and last line:

TextSelection text = (EnvDTE.TextSelection)_applicationObject.ActiveDocument.Selection;
text.SmartFormat(); //  sets the correct indention als studio
/* the following lines will expand the selection to whole lines: */
int lineSpan = text.BottomPoint.Line - text.TopPoint.Line;
text.MoveToPoint(text.TopPoint,false);                      
text.StartOfLine(vsStartOfLineOptions.vsStartOfLineOptionsFirstColumn,false);                       
text.LineDown(true,lineSpan);                       
text.EndOfLine(true);
/* and now my custom textformatting */
text.Insert(someCoolObjectThatFormatsText.Format(text.Text),(int)vsInsertFlags.vsInsertFlagsContainNewText);                                                                                    
text.Collapse();

I don't really know wether this is a good way to alter textselections but it works fine and is way faster than the original addin code