说明：请在工程中引用“Microsoft Word 9.0 object library”的Microsoft COM组件。该组件提供的类和方法来读取Word文档。

using System;
using System.IO;
using System.Reflection;
using Word;   

//----------------------------------------------------------------------

     string WordContent = "";
     object saveChanges = WdSaveOptions.wdDoNotSaveChanges;
     Word.Application app = new ApplicationClass();
     try
     {
      object fileName = fileDoc.Value;

      object optional= Missing.Value;
      object visible=true;
      if(File.Exists(fileName.ToString()))
      {
       Word.Document doc = app.Documents.Open(
        ref fileName,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref optional,
        ref visible);

       object first = 0;
       object units = WdUnits.wdCharacter;
       object last=doc.Characters.Count;
  
       Range    range= doc.Range(ref first, ref last);

       //替换
       #region 方法一，特点是非常简单
       //Word.range.Text = range.Text.Replace(txtOldValue.Text, txtNewValue.Text);
       #endregion

       #region 方法二，特别是可以实现复杂的查找替换
       Word.Find finder = range.Find;
       finder.ClearFormatting();
     
       object missingValue = Type.Missing;
       object findStr = txtOldValue.Text;
       object replaceStr = txtNewValue.Text;
       object replaceArea = Word.WdReplace.wdReplaceAll;

       if (finder.Execute(ref findStr, ref missingValue, ref missingValue,
        ref missingValue, ref missingValue, ref missingValue,
        ref missingValue, ref missingValue, ref missingValue,
        ref replaceStr, ref replaceArea, ref missingValue,
        ref missingValue, ref missingValue, ref missingValue))
       {
        //Text found,and replaceed
        //range.Select();
       }

       #endregion

       WordContent = "成功替换 " + txtOldValue.Text + " at " + DateTime.Now.ToString();
       saveChanges = WdSaveOptions.wdSaveChanges;
  
      }
      else
      {
       WordContent = "指定目录下的无该文件";
      }

      txtContent.Text = WordContent;
     
     }
     catch(Exception Ex)
     {
      txtContent.Text =     Ex.Message ;
     }
     finally
     {
      //退出保存
      object originalFormat = Missing.Value;
      object routeDocument = Missing.Value;
      app.Quit(ref saveChanges, ref originalFormat, ref routeDocument);
      app = null;

     }