using System.Reflection;
using Microsoft.Office.Core;//Referencia al objeto Office
using Microsoft.Office.Interop.Word;
using Word = Microsoft.Office.Interop.Word;
using WordI = Microsoft.Office.Interop.Word;

             
            WordI.Application appI = new WordI.Application();//instancia

            int errors = 0;
            if (textBox1.Text.Length > 0)
            {
                appI.Visible = false;
                object template = Missing.Value;
                object newTemplate = Missing.Value;
                object documentType = Missing.Value;
                object visible = true; // evita despliegue del documento word
                Word._Document doc1 = appI.Documents.Add(ref template, ref newTemplate, ref documentType, ref visible);
                doc1.Words.First.InsertBefore(textBox1.Text);
                Word.ProofreadingErrors spellErrorsColl = doc1.SpellingErrors;
                errors = spellErrorsColl.Count;
                object optional = Missing.Value;
                doc1.Content.LanguageID = Word.WdLanguageID.wdEnglishUS; //Custumiza el Idioma a Usar

                doc1.CheckSpelling(ref optional, ref optional, ref optional, ref optional, ref optional, ref optional,
                    ref optional, ref optional, ref optional, ref optional, ref optional, ref optional);
                
                label1.Text = errors + "Errores Corregidos ";//Muestra errores encontrados (a veces)
                object first = 0;
                object last = doc1.Characters.Count - 1;
                textBox1.Text = doc1.Range(ref first, ref last).Text;
            }

            object saveChanges = false;
            object originalFormat = Missing.Value;
            object routeDocument = Missing.Value;
            appI.Quit(ref saveChanges, ref originalFormat, ref routeDocument);//cierra doc