Csv下载在VB.NET中变得非常慢 [英] Csv download getting very slow in VB.NET

问题描述

大家好，

我需要从vb.net下载asp.net的csv文件

i已经从vb.net下载了csv文件

我提醒你的那一刻，当我下载少于50行时，文件下载速度非常快，但是当我下载超过100行时，它变得非常慢（意味着在5分钟后出现因为数据非常庞大） ）

那么解决这个问题我需要处理的关键步骤是什么。



请在下面找到我的代码，

使用dt As New DataTable（）
 Adp.Fill（dt）
 
'将CSV文件数据构建为逗号分隔的字符串。 
 Dim csv As String = String.Empty 
 
 For Each Column As DataColumn in dt.Columns 
'添加CSV文件的标题行。 
 csv + = column.ColumnName +，c 
 
 Next 
 
'添加新行。 
 csv + = vbCr& vbLf 
 
 For Each row As DataRow in dt.Rows 
 For Each column As DataColumn in dt.Columns 
'添加数据行。 
 csv + = row（column.ColumnName）.ToString（）。Replace（，，;）+，c 
 Next 
 
'添加新行。 
 csv + = vbCr& vbLf 
下一步
 
'下载CSV文件。 
 Response.Clear（）
 Response.Buffer = True 
 Response.AddHeader（content-disposition，attachment; filename = SqlExport.csv）
 Response.Charset = 
 Response.ContentType =application / text
 Response.Output.Write（csv）
 Response.Flush（）
 Response.End（）
 End使用

提前感谢。





问候，

stellus。



我尝试过：



csv下载在vb.net中变得非常慢

解决方案

使用 StringBuilder（）： https://www.dotnetperls.com/stringbuilder-vbnet [ ^ ]

加速代码的一个小技巧

  Dim  csv 正如 字符串 = 字符串 .Empty 
   Dim  row_csv 作为 字符串  
 
 ... 
 
 对于 每个行 As  DataRow 在 dt.Rows 
  row_csv =  String  .Empty  
 对于 每个列 As  DataColumn 在 dt.Columns 
 ' 添加数据行。 
 行_  csv + = row（column.ColumnName）.ToString（）。替换（ ，， < span class =code-string>;）+  ， c 
 下一步 
 
 ' 添加新行。 
 行_  csv + = vbCr& vbLf 
  csv + = row_csv  
 下一步 
 

Hi All,
I need to download csv file from asp.net with vb.net
i have done the download csv file from vb.net
The moment i raise you that, when i download less than 50 rows then the file download very fast but when i download more than 100 rows then it has come very slow (means come around after 5 minutes because data is very huge)
So what is the essential step i need to handle for this issue resolved.

Please find my code below,

Using dt As New DataTable()
                  Adp.Fill(dt)

                  'Build the CSV file data as a Comma separated string.
                  Dim csv As String = String.Empty

                  For Each column As DataColumn In dt.Columns
                      'Add the Header row for CSV file.
                      csv += column.ColumnName + ","c

                  Next

                  'Add new line.
                  csv += vbCr & vbLf

                  For Each row As DataRow In dt.Rows
                      For Each column As DataColumn In dt.Columns
                          'Add the Data rows.
                          csv += row(column.ColumnName).ToString().Replace(",", ";") + ","c
                      Next

                      'Add new line.
                      csv += vbCr & vbLf
                  Next

                  'Download the CSV file.
                  Response.Clear()
                  Response.Buffer = True
                  Response.AddHeader("content-disposition", "attachment;filename=SqlExport.csv")
                  Response.Charset = ""
                  Response.ContentType = "application/text"
                  Response.Output.Write(csv)
                  Response.Flush()
                  Response.End()
              End Using

thanks in advance.


regards,
stellus.

What I have tried:

csv download getting very slow in vb.net

解决方案

Use a StringBuilder() : https://www.dotnetperls.com/stringbuilder-vbnet[^]

A little trick to speedup your code

Dim csv As String = String.Empty
Dim row_csv As String

...

For Each row As DataRow In dt.Rows
    row_csv = String.Empty
    For Each column As DataColumn In dt.Columns
        'Add the Data rows.
        row_csv += row(column.ColumnName).ToString().Replace(",", ";") + ","c
    Next

    'Add new line.
    row_csv += vbCr & vbLf
    csv += row_csv
Next

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