Write to CSV file and export it

Question

In C  ASP net  could someone show me how I can write entries from an Array List to a CSV file on the server and then open the file  I think the second part would be something like - Response Redirect  http   myserver com file csv    however not sure on how to write the file on the server   Also if this page is accessed by many users  is it better to generate a new CSV file every time or overwrite the same file  Would there be any read write lock issues if both users try accessing the same CSV file etc      Update   This is probably a silly question and I have searched on Google but I m not able to find a definitive answer - how do you write a CSV file to the webserver and export it in C  ASP net  I know how to generate it but I would like to save it to www mysite com my csv and then export it

User · Answer

check out csvreader writer library at http   www codeproject com KB cs CsvReaderAndWriter aspx

User · Answer

Here is a CSV action result I wrote that takes a DataTable and converts it into CSV  You can return this from your view and it will prompt the user to download the file  You should be able to convert this easily into a List compatible form or even just put your list into a DataTable   using System  using System Text  using System Collections Generic  using System Linq  using System Web  using System Web Mvc  using System Data   namespace Detectent Analyze ActionResults       public class CSVResult   ActionResult                    lt summary gt              Converts the columns and rows from a data table into an Microsoft Excel compatible CSV file               lt  summary gt               lt param name  dataTable  gt  lt  param gt               lt param name  fileName  gt The full file name including the extension  lt  param gt          public CSVResult DataTable dataTable  string fileName                        Table   dataTable              FileName   fileName                     public string FileName   get  protected set            public DataTable Table   get  protected set                public override void ExecuteResult ControllerContext context                        StringBuilder csv   new StringBuilder 10   Table Rows Count   Table Columns Count                for  int c   0  c  lt  Table Columns Count  c                                  if  c  gt  0                      csv Append                       DataColumn dc   Table Columns c                   string columnTitleCleaned   CleanCSVString dc ColumnName                   csv Append columnTitleCleaned                             csv Append Environment NewLine               foreach  DataRow dr in Table Rows                                StringBuilder csvRow   new StringBuilder                    for int c   0  c  lt  Table Columns Count  c                                          if c    0                          csvRow Append                            object columnValue   dr c                       if  columnValue    null                          csvRow Append                          else                                               string columnStringValue   columnValue ToString                              string cleanedColumnValue   CleanCSVString columnStringValue                            if  columnValue GetType      typeof string   amp  amp   columnStringValue Contains                                                             cleanedColumnValue         cleanedColumnValue     Prevents a number stored in a string from being shown as 8888E 24 in Excel  Example use is the AccountNum field in CI that looks like a number but is really a string                                                    csvRow Append cleanedColumnValue                                                           csv AppendLine csvRow ToString                                HttpResponseBase response   context HttpContext Response              response ContentType    text csv               response AppendHeader  Content-Disposition    attachment filename     this FileName               response Write csv ToString                        protected string CleanCSVString string input                        string output          input Replace               Replace   r n        Replace   r        Replace   n                           return output

User · Answer

Here s a very simple free open-source CsvExport class for C   There s an ASP NET MVC example at the bottom   https   github com jitbit CsvExport  It takes care about line-breaks  commas  escaping quotes  MS Excel compatibilty    Just add one short  cs file to your project and you re good to go    disclaimer  I m one of the contributors

User · Answer

Rom  you re doing it wrong   You don t want to write files to disk so that IIS can serve them up   That adds security implications as well as increases complexity   All you really need to do is save the CSV directly to the response stream   Here s the scenario   User wishes to download csv   User submits a form with details about the csv they want   You prepare the csv  then provide the user a URL to an aspx page which can be used to construct the csv file and write it to the response stream   The user clicks the link   The aspx page is blank  in the page codebehind you simply write the csv to the response stream and end it     You can add the following to the  I believe this is correct  Load event   string attachment    attachment  filename MyCsvLol csv   HttpContext Current Response Clear    HttpContext Current Response ClearHeaders    HttpContext Current Response ClearContent    HttpContext Current Response AddHeader  content-disposition   attachment   HttpContext Current Response ContentType    text csv   HttpContext Current Response AddHeader  Pragma    public     var sb   new StringBuilder    foreach var line in DataToExportToCSV    sb AppendLine TransformDataLineIntoCsv line     HttpContext Current Response Write sb ToString       writing to the response stream code ganked from here

User · Answer

A comment about Will s answer  you might want to replace HttpContext Current Response End    with HttpContext Current ApplicationInstance CompleteRequest     The reason is that Response End   throws a System Threading ThreadAbortException   It aborts a thread   If you have an exception logger  it will be littered with ThreadAbortExceptions  which in this case is expected behavior   Intuitively  sending a CSV file to the browser should not raise an exception   See here for more Is Response End   considered harmful

User · Answer

How to write to a file  easy search in Google      1st Search Result  As far as creation of the file each time a user accesses the page     each access will act on it s own behalf   You business case will dictate the behavior   Case 1 - same file but does not change  this type of case can have multiple ways of being defined    You would have logic that created the file when needed and only access the file if generation is not needed    Case 2 - each user needs to generate their own file   You would decide how you identify each user  create a file for each user and access the file they are supposed to see     this can easily merge with Case 1   Then you delete the file after serving the content or not if it requires persistence    Case 3 - same file but generation required for each access   Use Case 2  this will cause a generation each time but clean up once accessed

[c#] Write to CSV file and export it?

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