作者：未知 来源：月光软件站 加入时间：2005-2-28　月光软件站

通过.NET上传图象

作者：Chris Khoo  翻译：tigerwen01

以前，通过ASP上传图象（图象的大小、类型都受到限制）一般都是要借助外部组件来完成，.NET的出现，使这一工作变得非常容易并且可以随便的使用Bitmap和Image类型。

在这个指导思想下，我将按照以下步骤（在你要上传图象文件上）创建一个简单的WEB窗体，该窗体将判断上传的文件是否是JPEG文件、判断该文件是否存在（必要时你可以重命名）。

1、  创建一个新Web 应用程序项目；

2、  打开Web 窗体；

3、  在窗体上面添加一个HTML表单，并把它转换成服务器控件。在这个例子里，该文件将命名为filUpload；（把HTML转换成服务器控件的方法是，在它的上面右击鼠标然后选择Run As Server Control）

4、  切换到HTML view并添加/更改FORM标签的enctype属性为multipart/form-data。如：enctype="multipart/form-data"。

5、  在Web窗体上添加一个BUTTON并命名为btnUpload。

6、  向Web应用程序添加一个folder called /images。

7、  在窗体上添加一个Web Form Image并命名为imgPicture，设置宽度和高度分别为160和120。

8、  添加一个Label控件并命名为lblOutput。显示当在上传的过程中发生的任何错误。

9、  给按钮btnUpload的单击事件添加如下代码：（如果你想分析以下代码的细节，你可以把下面的代码复制粘贴到VS.NET IDE集成开发环境。）

1.     private void btnUpload_Click(object sender, System.EventArgs e)

2.     {

3.         // Initialize variables

4.         string sSavePath;

5.         string sThumbExtension;

6.         int intThumbWidth;

7.         int intThumbHeight;

8.      

9.         // Set constant values

10.      sSavePath = "images/";

11.      sThumbExtension = "_thumb";

12.      intThumbWidth = 160;

13.      intThumbHeight = 120;

14.   

15.      // If file field isn’t empty

16.      if (filUpload.PostedFile != null)

17.      {

18.          // Check file size (mustn’t be 0)

19.          HttpPostedFile myFile = filUpload.PostedFile;

20.          int nFileLen = myFile.ContentLength;

21.          if (nFileLen == 0)

22.          {

23.              lblOutput.Text = "No file was uploaded.";

24.              return;

25.          }

26.   

27.          // Check file extension (must be JPG)

28.          if (System.IO.Path.GetExtension(myFile.FileName).ToLower() != ".jpg")

29.          {

30.              lblOutput.Text = "The file must have an extension of JPG";

31.              return;

32.          }

33.   

34.          // Read file into a data stream

35.          byte[] myData = new Byte[nFileLen];

36.          myFile.InputStream.Read(myData,0,nFileLen);

37.   

38.          // Make sure a duplicate file doesn’t exist.  If it does, keep on appending an 

39.          // incremental numeric until it is unique

40.          string sFilename = System.IO.Path.GetFileName(myFile.FileName);

41.          int file_append = 0;

42.          while (System.IO.File.Exists(Server.MapPath(sSavePath + sFilename)))

43.          {

44.              file_append++;

45.              sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)

46.                               + file_append.ToString() + ".jpg";

47.          }

48.   

49.          // Save the stream to disk

50.          System.IO.FileStream newFile

51.                  = new System.IO.FileStream(Server.MapPath(sSavePath + sFilename), 

52.                                             System.IO.FileMode.Create);

53.          newFile.Write(myData,0, myData.Length);

54.          newFile.Close();

55.   

56.          // Check whether the file is really a JPEG by opening it

57.          System.Drawing.Image.GetThumbnailImageAbort myCallBack = 

58.                         new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);

59.          Bitmap myBitmap;

60.          try

61.          {

62.              myBitmap = new Bitmap(Server.MapPath(sSavePath + sFilename));

63.   

64.              // If jpg file is a jpeg, create a thumbnail filename that is unique.

65.              file_append = 0;

66.              string sThumbFile = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)

67.                                                       + sThumbExtension + ".jpg";

68.              while (System.IO.File.Exists(Server.MapPath(sSavePath + sThumbFile)))

69.              {

70.                  file_append++;

71.                  sThumbFile = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + 

72.                                 file_append.ToString() + sThumbExtension + ".jpg";

73.              }

74.   

75.              // Save thumbnail and output it onto the webpage

76.              System.Drawing.Image myThumbnail

77.                      = myBitmap.GetThumbnailImage(intThumbWidth, 

78.                                                   intThumbHeight, myCallBack, IntPtr.Zero);

79.              myThumbnail.Save (Server.MapPath(sSavePath + sThumbFile));

80.              imgPicture.ImageUrl = sSavePath + sThumbFile;

81.   

82.              // Displaying success information

83.              lblOutput.Text = "File uploaded successfully!";

84.   

85.              // Destroy objects

86.              myThumbnail.Dispose();

87.              myBitmap.Dispose();

88.          }

89.          catch (ArgumentException errArgument)

90.          {

91.              // The file wasn't a valid jpg file

92.              lblOutput.Text = "The file wasn't a valid jpg file.";

93.              System.IO.File.Delete(Server.MapPath(sSavePath + sFilename));

94.          }

95.      }

96.  }

97.   

98.  public bool ThumbnailCallback()

99.  {

100.         return false;

}     

10．运行以上创建的 Web页（webpage），并分别使用JPG文件和其他类型的文件来测试错误检查（error-checking）机制。

11. 如果你有什么问题或建议，请给作者留言。

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关于Chris Khoo

I was born in Malaysia on 13th February 1982 and moved to Australia when I was 8. I also started programming around that time as well in GWBasic . Over the years, I picked up Assembly, Pascal, and C/C++.

In my teen/adult years when Windows programming became the norm, I also learnt some MFC, Visual Basic, and Java and have completed some web projects utilizing ASP and also created Office VBA macros for businesses.

Within this time, I picked up a MCSD and MCSE, however I finally chose to go to university instead of working a full time software development job.

Currently, at age 20, I am studying Commerce(Accounting) and Information Technology at the University of Queensland, and it is a blast.

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