using System.Reflection;
using Word = Microsoft.Office.Interop.Word;

namespace WordSpell
{
    public partial class Form1 : System.Windows.Forms.Form
    {
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Label label1;

        public Form1()  //constructor
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, System.EventArgs e)
        {
            Word.Application app = new Word.Application();

            int errors = 0;
            if (textBox1.Text.Length > 0)
            {
                app.Visible = false;

                // Setting these variables is comparable to passing null to the function.
                // This is necessary because the C# null cannot be passed by reference.
                object template = Missing.Value;
                object newTemplate = Missing.Value;
                object documentType = Missing.Value;
                object visible = true;

                Word._Document doc1 = app.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.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 + " errors corrected ";
                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;

            app.Quit(ref saveChanges, ref originalFormat, ref routeDocument);
        }
    }
}