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使用ASP.NET上传图片汇总(二)

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4 客户端检查上传文件类型(以上传图片为例)

  1. <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default"
    %>
  3. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  5. <html xmlns="http://www.w3.org/1999/xhtml" >
  6. <head runat="server">
  7. <title>客户端检查上传文件类型</title>
  8. <script language="javascript">
  9. function Check_FileType()
  10. {
  11. var str=document.getElementById("FileUpload1").value;
  12. var pos=str.lastIndexOf(".");
  13. var lastname=str.substring(pos,str.length);
  14. if(lastname.toLowerCase()!=".jpg"&&lastname.toLowerCase()!=".gif")
  15. {
  16. alert("您上传的文件类型为"+lastname+"，图片必须为.jpg,.gif类型");
  17. return false;
  18. }
  19. else
  20. {
  21. return true;
  22. }
  23. }
  24. </script>
  25. </head>
  26. <body>
  27. <form id="form1" runat="server">
  28. <div>
  29. <table>
  30. <tr>
  31. <td colspan="2">
  32. 客户端检查上传文件类型</td>
  33. </tr>
  34. <tr>
  35. <td style="width: 444px">
  36. <asp:FileUpload ID="FileUpload1" runat="server" Width="432px" /></td>
  37. <td style="width: 80px">
  38. <asp:Button ID="bt_upload" runat="server" Text="上传图片" OnClick="bt_upload_Click"
    OnClientClick=    "return Check_FileType()" /></td>
  39. </tr>
  40. <tr>
  41. <td colspan="2" style="height: 21px">
  42. <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="515px"></asp:Label></td>
  43. </tr>
  44. </table>
  45. </div>
  46. </form>
  47. </body>
  48. </html>

注意：点击上传时先触发客户端事件OnClientClick="return Check_FileType()"

  1. using System;
  2. using System.Data;
  3. using System.Configuration;
  4. using System.Web;
  5. using System.Web.Security;
  6. using System.Web.UI;
  7. using System.Web.UI.WebControls;
  8. using System.Web.UI.WebControls.WebParts;
  9. using System.Web.UI.HtmlControls;
  11. public partial class _Default : System.Web.UI.Page
  12. {
  13. protected void Page_Load(object sender, EventArgs e)
  14. {
  16. }
  18. protected
    void bt_upload_Click(object sender, EventArgs e)
  19. {
  20. try
  21. {
  22. if (FileUpload1.PostedFile.FileName ==
    "")
  23. {
  24. this.lb_info.Text =
    "请选择文件！";
  25. }
  26. else
  27. {
  28. string filepath = FileUpload1.PostedFile.FileName;
  29. //if (!IsAllowedExtension(FileUpload1))
  30. //{
  31. // this.lb_info.Text = "上传文件格式不正确！";
  32. //}
  33. if (IsAllowedExtension(FileUpload1) ==
    true)
  34. {
  35. string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
  36. string serverpath = Server.MapPath("~/images/") + filename;
  37. FileUpload1.PostedFile.SaveAs(serverpath);
  38. this.lb_info.Text =
    "上传成功！";
  39. }
  40. else
  41. {
  42. this.lb_info.Text =
    "请上传图片！";
  43. }
  44. }
  45. }
  46. catch (Exception ex)
  47. {
  48. this.lb_info.Text =
    "上传发生错误！原因：" + ex.ToString();
  49. }
  50. }
  51. private static
    bool IsAllowedExtension(FileUpload upfile)
  52. {
  53. string strOldFilePath =
    "";
  54. string strExtension="";
  55. string[] arrExtension ={
    ".gif", ".jpg",
    ".bmp", ".png" };
  56. if (upfile.PostedFile.FileName !=
    string.Empty)
  57. {
  58. strOldFilePath = upfile.PostedFile.FileName;//获得文件的完整路径名
  59. strExtension = strOldFilePath.Substring(strOldFilePath.LastIndexOf("."));//获得文件的扩展名，如：.jpg
  60. for (int i = 0; i < arrExtension.Length; i++)
  61. {
  62. if (strExtension.Equals(arrExtension[i]))
  63. {
  64. return true;
  65. }
  66. }
  67. }
  68. return false;
  69. }
  70. }

注意：若去掉客户端的脚本和客户端事件OnClientClick="return Check_FileType()"，在后台代码

  1. //if (!IsAllowedExtension(FileUpload1))
  2. //{
  3. // this.lb_info.Text = "上传文件格式不正确！";
  4. //}
  5. if (IsAllowedExtension(FileUpload1) ==
    true)

改为：

  1. if (!IsAllowedExtension(FileUpload1))
  2. {
  3. this.lb_info.Text = "上传文件格式不正确！";
  4. }
  5. else if (IsAllowedExtension(FileUpload1) ==
    true)

即变成服务器端检查上传文件类型。

5 服务器端检查上传文件的类型（文件内部真正的格式）

  1. <body>
  2. <form id="form1" runat="server">
  3. <div>
  4. <table>
  5. <tr>
  6. <td colspan="2">
  7. 服务器检查上传文件类型</td>
  8. </tr>
  9. <tr>
  10. <td style="width: 444px">
  11. <asp:FileUpload ID="FileUpload1" runat="server" Width="432px" /></td>
  12. <td style="width: 80px">
  13. <asp:Button ID="bt_upload" runat="server" Text="上传图片" OnClick="bt_upload_Click" /></td>
  14. </tr>
  15. <tr>
  16. <td colspan="2" style="height: 21px">
  17. <asp:Label ID="lb_info" runat="server" ForeColor="Red" Width="515px"></asp:Label></td>
  18. </tr>
  19. </table>
  20. </div>
  21. </form>
  22. </body>

后台代码：

  1. using System;
  2. using System.Data;
  3. using System.Configuration;
  4. using System.Web;
  5. using System.Web.Security;
  6. using System.Web.UI;
  7. using System.Web.UI.WebControls;
  8. using System.Web.UI.WebControls.WebParts;
  9. using System.Web.UI.HtmlControls;
  10. using System.IO;
  12. public partial
    class _Default : System.Web.UI.Page
  13. {
  14. protected
    void Page_Load(object sender, EventArgs e)
  15. {
  17. }
  18. protected
    void bt_upload_Click(object sender, EventArgs e)
  19. {
  20. try
  21. {
  22. if (FileUpload1.PostedFile.FileName ==
    "")
  23. {
  24. this.lb_info.Text =
    "请选择文件！";
  25. }
  26. else
  27. {
  28. string filepath = FileUpload1.PostedFile.FileName;
  29. if (IsAllowedExtension(FileUpload1) ==
    true)
  30. {
  31. string filename = filepath.Substring(filepath.LastIndexOf("//") + 1);
  32. string serverpath = Server.MapPath("images/") + filename;
  33. FileUpload1.PostedFile.SaveAs(serverpath);
  34. this.lb_info.Text =
    "上传成功！";
  35. }
  36. else
  37. {
  38. this.lb_info.Text =
    "请上传图片";
  39. }
  40. }
  41. }
  42. catch (Exception error)
  43. {
  44. this.lb_info.Text =
    "上传发生错误！原因：" + error.ToString();
  45. }
  46. }
  47. private static
    bool IsAllowedExtension(FileUpload upfile)
  48. {
  49. FileStream fs = new FileStream(upfile.PostedFile.FileName, FileMode.Open, FileAccess.Read);
  50. BinaryReader r = new BinaryReader(fs);
  51. string fileclass = "";
  52. byte buffer;
  53. try
  54. {
  55. buffer = r.ReadByte();
  56. fileclass = buffer.ToString();
  57. buffer = r.ReadByte();
  58. fileclass += buffer.ToString();
  59. }
  60. catch
  61. {
  63. }
  64. r.Close();
  65. fs.Close();
  66. if (fileclass ==
    "255216" || fileclass == "7173"||fileclass=="6677"||fileclass=="13780")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar
  67. {
  68. return true;
  69. }
  70. else
  71. {
  72. return false;
  73. }
  74. }
  75. }
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