拼写检查器使用单词

我正在用c#为拼写检查器编写一段代码。我在网上找到了这个代码。我是c#的新手，无法理解代码。

我在以下网站上找到了此代码：http://www.codeproject.com/Articles/4572/Using-Word-s-spellchecker-in-C

我可以了解一下代码中实际发生的事情的一般指南吗：

using Word;
using System.Reflection;

private void button1_Click(object sender, System.EventArgs e) 
{ 
    fSpellCheck(textBox1 , label1 ); 
}

public void fSpellCheck(TextBox tBox, Label lLbl) 
{ 
    int iErrorCount = 0; 
    Word.Application app = new Word.Application(); 
    if (tBox.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; 
        object optional = Missing.Value; 
        _Document doc = app.Documents.Add(ref template, 
           ref newTemplate, ref documentType, ref visible); 
        doc.Words.First.InsertBefore (tBox.Text ); 
        Word.ProofreadingErrors we = doc.SpellingErrors; 
        iErrorCount = we.Count; 
        doc.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); 
        if (iErrorCount == 0) 
            lLbl.Text = "Spelling OK. No errors corrected "; 
        else if (iErrorCount == 1) 
            lLbl.Text = "Spelling OK. 1 error corrected "; 
        else 
            lLbl.Text = "Spelling OK. " + iErrorCount + 
                                    " errors corrected "; 
        object first=0; 
        object last=doc.Characters.Count -1; 
        tBox.Text = doc.Range(ref first, ref last).Text; 
    } 
    else 
        lLbl.Text = "Textbox is empty"; 
    object saveChanges = false; 
    object originalFormat = Missing.Value; 
    object routeDocument = Missing.Value; 
    app.Quit(ref saveChanges, ref originalFormat, ref routeDocument); 
}