I've solved it but it's really really slow, so any new ideas are welcomed.
using Microsoft.Office.Interop.Word;
class WordProofing
{
private Application _wordApp;
private readonly Document _wordDoc;
private static object _oEndOfDoc = "\\endofdoc";
public WordProofing()
{
_wordApp = new Application { Visible = false };
_wordDoc = _wordApp.Documents.Add();
}
public void Close()
{
_wordDoc.Close(WdSaveOptions.wdDoNotSaveChanges);
_wordApp.Quit();
}
public string Proof(string proofText)
{
Range wRng = _wordDoc.Bookmarks.get_Item(ref _oEndOfDoc).Range;
wRng.Text = proofText;
ProofreadingErrors spellingErros = wRng.SpellingErrors;
foreach (Range spellingError in spellingErros)
{
SpellingSuggestions spellingSuggestions =
_wordApp.GetSpellingSuggestions(spellingError.Text,IgnoreUppercase:true);
foreach (SpellingSuggestion spellingSuggestion in spellingSuggestions)
{
spellingError.Text = spellingSuggestion.Name;
break;
}
}
string str = wRng.Text;
wRng.Text = "";
return str;
}
}