Asp.net 下载较大文件

前段时间做了一个Export 数据到Excel的功能。数据存储在Tree View中，父子关系明确。要求在Excel中也要明确父子关系。不可避免的，需要在后台先分析TreeView中的父子关系然后再生成Excel，耗费时间。只要数据量稍微大些，父子关系复杂些，下载Excel就会很慢，而且下载不成功。原因？Rquest在等待较长时间后自动关闭了。

解决的方法就是将Request header中的Connection 属性设置为Keep-alive的。

关于下载部分，我写了两种方法，效果感觉差不多。

1。应用Response.WriteFile

 1 private void CreateExcel()
 2         {
 3             string windowsTempDirPath = Utility.GetWindowsTempDirConfigKey();
 4             string localPath = windowsTempDirPath + "GeneratedTemplate.xlsx";
 5 
 6             File.Copy(Server.MapPath("~/Templates/ExcelTemplate.xlsx"), localPath, true);
 7 
 8             using (SpreadsheetDocument myWorkbook = SpreadsheetDocument.Open(localPath, true))
 9             {
10                 this.workbookPart = myWorkbook.WorkbookPart;
11                 this.workbookPart.WorkbookStylesPart.Stylesheet = Utility.CreateStylesheet();
12                 this.worksheetPart = workbookPart.WorksheetParts.First();
13                 this.sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();
14 
15                 Row headerRow = CreateHeaderRow();
16                 this.sheetData.AppendChild(headerRow);
17 
18                 var tempTree = new TreeView();
19                 TreeNode rootNode = this.CreateRootNode(
20                     this.GrpDisplayName.Value,
21                     this.GrpDomain.Value,
22                     this.GrpGuid.Value,
23                     this.GrpAlias.Value,
24                     this.GrpType.Value);
25                 tempTree.Nodes.Add(rootNode);
26                 this.GroupMembershipItems = HttpContext.Current.Session["GroupMembershipItems"] as List<GroupMembershipItem>;
27                 this.PrepareTreeView(tempTree, rootNode, false);
28                 this.AddTreeNodeDataToExcel(tempTree.Nodes);
29             }
30 //download excel
31             HttpContext.Current.Response.ClearContent();
32             HttpContext.Current.Response.ClearHeaders();
33             HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=GroupMembershipReport.xlsx");
34             HttpContext.Current.Response.ContentType = "application/vnd.openxmlformats-officedocument." + "spreadsheetml.sheet";
35             FileStream fis = null;
36             try
37             {
38                 fis = File.OpenRead(localPath);
39                 long dataToRead = fis.Length;
40                 HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());
41 //keep connection alive
42                 Response.AddHeader("Connection", "Keep-Alive");
43                 Response.ContentEncoding = System.Text.Encoding.UTF8;
44 
45                 Response.WriteFile(localPath);
46                 Response.Flush();
47                 Response.Close();
48                 System.IO.File.Delete(localPath);
49             }
50             finally
51             {
52                 if (fis != null)
53                 {
54                     fis.Close();
55                 }
56                 Response.Flush();
57                 Response.Close();
58             }
59         }

2. 使用Response.OutputStream.Write

 1 private void CreateExcel()
 2         {
 3             string windowsTempDirPath = Utility.GetWindowsTempDirConfigKey();
 4             string localPath = windowsTempDirPath + "GeneratedTemplate.xlsx";
 5 
 6             File.Copy(Server.MapPath("~/Templates/ExcelTemplate.xlsx"), localPath, true);
 7 
 8             using (SpreadsheetDocument myWorkbook = SpreadsheetDocument.Open(localPath, true))
 9             {
10                 this.workbookPart = myWorkbook.WorkbookPart;
11                 this.workbookPart.WorkbookStylesPart.Stylesheet = Utility.CreateStylesheet();
12                 this.worksheetPart = workbookPart.WorksheetParts.First();
13                 this.sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();
14 
15                 Row headerRow = CreateHeaderRow();
16                 this.sheetData.AppendChild(headerRow);
17 
18                 var tempTree = new TreeView();
19                 TreeNode rootNode = this.CreateRootNode(
20                     this.GrpDisplayName.Value,
21                     this.GrpDomain.Value,
22                     this.GrpGuid.Value,
23                     this.GrpAlias.Value,
24                     this.GrpType.Value);
25                 tempTree.Nodes.Add(rootNode);
26                 this.GroupMembershipItems = HttpContext.Current.Session["GroupMembershipItems"] as List<GroupMembershipItem>;
27                 this.PrepareTreeView(tempTree, rootNode, false);
28                 this.AddTreeNodeDataToExcel(tempTree.Nodes);
29             }
30             
31             HttpContext.Current.Response.ClearContent();
32             HttpContext.Current.Response.ClearHeaders();
33             HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=GroupMembershipReport.xlsx");
34             HttpContext.Current.Response.ContentType = "application/vnd.openxmlformats-officedocument." + "spreadsheetml.sheet";
35             FileStream fis = null;
36             try
37             {
38                 fis = File.OpenRead(localPath);
39                 long dataToRead = fis.Length;
40                 int readLength = 0;
41                 byte[] buffer = new byte[1000];
42 
43                 HttpContext.Current.Response.AddHeader("Content-Length", dataToRead.ToString());
44                 Response.AddHeader("Connection", "Keep-Alive");
45                 Response.ContentEncoding = System.Text.Encoding.UTF8;
46                 while (dataToRead > 0)
47                 {
48                     if (Response.IsClientConnected)
49                     {
50                         readLength = fis.Read(buffer, 0, 1000);
51                         Response.OutputStream.Write(buffer, 0, readLength);
52                         Response.Flush();
53                         buffer = new byte[1000];
54                         dataToRead = dataToRead - readLength;
55                     }
56                     else
57                     {
58                         dataToRead = -1;
59                         Logger.Write("client is not connected", "client");
60                     }
61                 }
62             }
63             catch (Exception e)
64             {
65                 throw e;
66             }
67             finally
68             {
69                 if (fis != null)
70                 {
71                     fis.Close();
72                 }
73                 Response.Flush();
74                 Response.Close();
75             }
76             //Response.WriteFile(localPath);
77             //Response.Flush();
78             //Response.Close();
79             System.IO.File.Delete(localPath);
80         }

下面是下载文件时使用IE Developer Tool获取到的Request Header和Response Header。当遭遇到Http Network等不好捕捉的问题时，这个Developer Tool会帮上大忙的。

posted on 2013-03-15 18:01 小凯Ki 阅读(153) 评论(0) 收藏举报