首先是预览图片，这个功能很好实现，无非就是创建一个html页面，嵌套一个<img>，为了限制图片类型，可以定义一个允许预览类型数组作为限制：
1 /// <summary> 2 /// 预览图片 3 /// </summary> 4 /// <param name="physicalPath"></param> 5 /// <param name="physicalDicPath"></param> 6 /// <returns></returns> 7 public string PreviewPic(string physicalPath, string physicalDicPath) 8 { 9 string imageName = Path.GetFileNameWithoutExtension(physicalPath); 10 string htmlName = imageName + ".html"; 11 if (!File.Exists(physicalDicPath + htmlName)) 12 { 13 FileStream fs = new FileStream(physicalDicPath + htmlName, FileMode.CreateNew); 14 StreamWriter sw = new StreamWriter(fs, Encoding.UTF8); 15 StringBuilder sb = new StringBuilder(); 16 sb.Append(@"<!DOCTYPE html> 17 <html lang = 'zh-CN'><head> 18 <meta http - equiv = 'Content-Type' content = 'text/html; charset=UTF-8'> 19 <meta http - equiv = 'X-UA-Compatible' content = 'IE=edge'> 20 <meta name = 'viewport' content = 'width=device-width, initial-scale=1'> 21 <title>图片预览</title> 22 <style> 23 .content 24 { 25 80%; 26 height:auto; 27 margin:0 auto; 28 padding:10px 20px; 29 } 30 img{ 31 80%; 32 height:auto; 33 margin: 10px 10%; 34 } 35 </style> 36 </head>"); 37 sb.Append(@"<body><div class='content'>"); 38 var TruePath = "http://" + HttpContext.Current.Request.Url.Authority + "/" + urlconvertor(physicalPath); 39 sb.Append(@"<img src='" + TruePath + "'/>"); 40 sb.Append(@"</div>"); 41 sb.Append(@"</body>"); 42 sw.Write(sb.ToString()); //这里是写入的内容 43 sw.Flush(); 44 sw.Close(); 45 } 46 var resultRul = "http://" + HttpContext.Current.Request.Url.Authority + "/" + urlconvertor(physicalDicPath + htmlName); 47 return resultRul; 48 }
然后就是预览excel文件，这个微软为我们提供了现成的方法，打开nuget管理，安装Microsoft.Office.Interop.Excel；经测试xls和xlsx格式都可以成功解析，然后代码如下：
1 /// <summary> 2 /// 预览Excel 3 /// </summary> 4 /// <param name="physicalPath">文件物理路径</param> 5 /// <param name="physicalDicPath">文件夹物理路径</param> 6 /// <returns>生成页面链接</returns> 7 public string PreviewExcel(string physicalPath, string physicalDicPath) 8 { 9 string htmlName = Path.GetFileNameWithoutExtension(physicalPath) + ".html"; 10 if (!File.Exists(physicalDicPath + htmlName)) 11 { 12 Microsoft.Office.Interop.Excel.Application application = null; 13 Microsoft.Office.Interop.Excel.Workbook workbook = null; 14 application = new Microsoft.Office.Interop.Excel.Application(); 15 object missing = Type.Missing; 16 object trueObject = true; 17 application.Visible = false; 18 application.DisplayAlerts = false; 19 workbook = application.Workbooks.Open(physicalPath, missing, trueObject, missing, missing, missing, 20 missing, missing, missing, missing, missing, missing, missing, missing, missing); 21 //Save Excel to Html 22 object format = Microsoft.Office.Interop.Excel.XlFileFormat.xlHtml; 23 String outputFile = Path.GetDirectoryName(physicalPath) + "\" + htmlName; 24 workbook.SaveAs(outputFile, format, missing, missing, missing, 25 missing, XlSaveAsAccessMode.xlNoChange, missing, 26 missing, missing, missing, missing); 27 workbook.Close(); 28 application.Quit(); 29 } 30 var resultRul = "http://" + HttpContext.Current.Request.Url.Authority + "/" + urlconvertor(physicalDicPath + htmlName); 31 return resultRul; 32 }
最后就是word的预览了，word的话有两个常见格式：doc，docx；在测试该方法的时候，打开doc格式的word，每次都会弹出转换格式的弹窗，上网查了一下，原来的
Documents.Open()
方法的第二个参数是：真正显示转换文件对话框，如果该文件不是Microsoft Word格式。所以我们只需要将 ConfirmConversions设置为false即可规避这个问题；代码如下：
1 /// <summary> 2 /// 预览Excel 3 /// </summary> 4 /// <param name="type">文件格式</param> 5 /// <param name="physicalPath">文件物理路径</param> 6 /// <param name="physicalDicPath">文件夹物理路径</param> 7 /// <returns>生成页面链接</returns> 8 public string PreviewWord(string physicalPath, string physicalDicPath) 9 { 10 string htmlName = Path.GetFileNameWithoutExtension(physicalPath) + ".html"; 11 if (!File.Exists(physicalDicPath + htmlName)) 12 { 13 Microsoft.Office.Interop.Word._Application application = null; 14 Microsoft.Office.Interop.Word._Document doc = null; 15 application = new Microsoft.Office.Interop.Word.Application(); 16 object missing = Type.Missing; 17 object trueObject = true; 18 object falseObject = false; 19 application.Visible = false; 20 application.DisplayAlerts = WdAlertLevel.wdAlertsNone; 21 doc = application.Documents.Open(physicalPath, falseObject, trueObject, missing, missing, missing, 22 missing, missing, missing, missing, missing, missing, missing, missing, missing, missing); 23 object format = format = Microsoft.Office.Interop.Word.WdSaveFormat.wdFormatHTML; 24 String outputFile = Path.GetDirectoryName(physicalPath) + "\" + htmlName; 25 doc.SaveAs(outputFile, format, missing, missing, missing, 26 missing, missing, missing, 27 missing, missing, missing, missing); 28 doc.Close(); 29 application.Quit(); 30 } 31 var resultRul= "http://"+HttpContext.Current.Request.Url.Authority +"/"+ urlconvertor(physicalDicPath + htmlName); 32 return resultRul; 33 }
最后是预览text，这个实现思想和预览图片是一样的，读取文档内容，填充到html页面上，代码如下：
1 /// <summary> 2 /// 预览Txt 3 /// </summary> 4 /// <param name="physicalPath">文件物理路径</param> 5 /// <param name="physicalDicPath">文件夹物理路径</param> 6 /// <returns>生成页面链接</returns> 7 public string PreviewTxt(string physicalPath, string physicalDicPath) 8 { 9 FileStream aFile = new FileStream(physicalPath, FileMode.Open); 10 //暂时不知道为什么获取的编码方式会导致读取的内容为空 11 //Encoding codeType = GetType(aFile); 12 StreamReader sr = new StreamReader(aFile, Encoding.GetEncoding("GB2312")); 13 var content= sr.ReadToEndAsync().Result.Replace(" ","</br>"); 14 string htmlName = Path.GetFileNameWithoutExtension(physicalPath) + ".html"; 15 if (!File.Exists(physicalDicPath + htmlName)) 16 { 17 FileStream fs = new FileStream(physicalDicPath + htmlName, FileMode.CreateNew); 18 StreamWriter sw = new StreamWriter(fs,Encoding.UTF8); 19 StringBuilder sb = new StringBuilder(); 20 sb.Append(@"<!DOCTYPE html> 21 <html lang = 'zh-CN'><head> 22 <meta http - equiv = 'Content-Type' content = 'text/html; charset=UTF-8'> 23 <meta http - equiv = 'X-UA-Compatible' content = 'IE=edge'> 24 <meta name = 'viewport' content = 'width=device-width, initial-scale=1'> 25 <title>文本预览</title> 26 <style> 27 .content 28 { 29 60%; 30 height:auto; 31 margin:0 auto; 32 border:1px solid #333; 33 padding:10px 20px; 34 } 35 </style> 36 </head>"); 37 sb.Append(@"<body><div class='content'>"); 38 sb.Append(@"<p>"); 39 sb.Append(content); 40 sb.Append(@"</p></div>"); 41 sb.Append(@"</body>"); 42 sw.Write(sb.ToString()); //这里是写入的内容 43 sw.Flush(); 44 sw.Close(); 45 } 46 sr.Close(); 47 var resultRul = "http://" + HttpContext.Current.Request.Url.Authority + "/" + urlconvertor(physicalDicPath + htmlName); 48 return resultRul; 49 }