I have to make an ASP.net form and only need to gather 3 fields: name, bday and email.
Do you think it's best to write the info to a csv or xml file, or do you think it's worth it to write to a SQL DB or something and then export from there to a file?
I'm of the opinion that just writing to a flat file is best because it's just going to need to be exported into a csv/xml file anyway so it can be appended to an excel file.
I'd use something like streamwriter or filestream in my C# submitbutton function:
StreamWriter sw = new StreamWriter(filename, true);
sw.WriteLine(string.Concat
( textBox1.Text
, textBox2.Text
, textBox3.Text
, textBox4.Text
, textBox5.Text
, textBox6.Text
, textBox7.Text ));
sw.Close();
Am I overlooking shortcomings of using csv and StreamWriter? Like do any weird things happen when the file gets to a certain size?
Also, how is Streamwriter compared to Filestream, or should I be looking at a different method entirely?
Even for small applications you will never regret using a database. Especially if they ever change / grow. Text files are a lot harder to make a change if you want to store other data.
File access for web applications be challenging at best. If you do use a Database I would ultimately look in to XML/XSD and using Data Sets.
Related
I have an ASP.NET application that helps the user create a Gridview with certain data in it. Once this table is generated I want the user to push a button and be able to save the table as an Excel document.There are two different methods I know of:
Using HtmlTextWriter with ContentType "application/vnd.ms-excel" to send the file as an HttpResponse. I use GridView1.RenderControl(htmlTextWriter) to render the gridview. This almost works, but the excel file always shows a warning when the file opens because the content doesn't match the extension. I have tried various content types to no avail. This makes sense I guess, because I'm using an HtmlWriter. It also doesn't seem a good practice.
The second thing I've tried is generating the Excel file using Office Automation. But for the file to be generated, I need to save it to disk and then read it again. From what I have read, this is the only way, because the Excel object only becomes a real Excel file once you save it. I found that the .saveas method from the Excel class would throw an exception because of write permissions, even if I tried to save in the App_Data folder. So I did some research and found that apparently Office Automation is discouraged for web services: https://support.microsoft.com/en-us/kb/257757
Microsoft does not currently recommend, and does not support,
Automation of Microsoft Office applications from any unattended,
non-interactive client application or component (including ASP,
ASP.NET, DCOM, and NT Services), because Office may exhibit unstable
behavior and/or deadlock when Office is run in this environment.
There surely must be a save way to have a website generate an Excel file and offer it to the user!? I can't imagine that this problem is unsolved or so rare that nobody cares about it, but yet I can't find any good solution to this.
the easiest (and best) way to create an excel file is by using epplus
Epplus sample for webapplication
using (ExcelPackage pck = new ExcelPackage())
{
ExcelWorksheet ws = pck.Workbook.Worksheets.Add("Demo");
//Load the datatable into the sheet, starting from cell A1. Print the column names on row 1
ws.Cells["A1"].LoadFromDataTable(tbl, true);
//Format the header for column 1-3
using (ExcelRange rng = ws.Cells["A1:C1"])
{
rng.Style.Font.Bold = true;
rng.Style.Fill.PatternType = ExcelFillStyle.Solid; //Set Pattern for the background to Solid
rng.Style.Fill.BackgroundColor.SetColor(Color.FromArgb(79, 129, 189)); //Set color to dark blue
rng.Style.Font.Color.SetColor(Color.White);
}
//Example how to Format Column 1 as numeric
using (ExcelRange col = ws.Cells[2, 1, 2 + tbl.Rows.Count, 1])
{
col.Style.Numberformat.Format = "#,##0.00";
col.Style.HorizontalAlignment = ExcelHorizontalAlignment.Right;
}
//Write it back to the client
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("content-disposition", "attachment; filename=ExcelDemo.xlsx");
Response.BinaryWrite(pck.GetAsByteArray());
}
is it possible to create a binary excel file in asp classic?
the common method is using this
Response.ContentType = "application/octet-stream"
Response.AddHeader "Content-Disposition", "attachment; filename=test.txt"
which is not a "true" excel file
In .net you could use the Microsoft.Office.Interop.Excel namespace - very easy to use, if you have access to .net i'd certainly go for that.
You say "in pure asp" - if this means without com objects etc - i dont think it's possible.
If however you wish to persevere with classic asp with the option of using a com object you can create full binary spreadsheets using the Interop com object - to do this you will need Excel installed on the webserver.
For example, to open a blank excel file on disk (i.e. a template), change a value and save the finished file:
'#### Ready Excel
Set ExcelApp = CreateObject("Excel.Application")
ExcelApp.Application.Visible = True
'#### Open a blank Excel File
Set ExcelBook = ExcelApp.workbooks.Open("d:\wwwroot2\blankTemplate.xls")
'#### Select a sheet and change the value of a cell
ExcelBook.Worksheets("SheetName").Cells(1, 1).Value = "Lorem Ipsum"
'#### Switch between sheets
ExcelBook.Worksheets("AnotherSheetName").Select
'#### Save the finished file with a different name (to leave the template ready for easy re-use)
ExcelBook.SaveAs "d:\wwwroot2\FinishedFile.xls"
'#### Tidy up
ExcelBook.Close
ExcelApp.Application.Quit
Set ExcelApp = Nothing
Set ExcelBook = Nothing
Good thing about this method is the interop com object mimics VBA methods etc very closely, so if your ever unsure how to do something, record a macro in excel, view the raw vba, the code it produces, specifically the methods and parameters would be very similar in most cases to the code you would use for the com object.
I'm currently patching an asp.net program where I need to be able to send an image to an SQL Server 2005 DB. It works fine when I use the asp:fileupload control, but the trick is that when the user deletes the image, I'm supposed to replace it with an image from the server saying "empty", in code-behind.
I know how to open, use and save text files in vb, but I can't find any information anywhere on how to open an image / binary file in a similar manner so that I can use it as an sql-parameter on the update query.
Below is an example of how easy it is to use a file from the fileupload control.
Dim t_id As Integer = Convert.ToInt32(Request.QueryString("id"))
open()
Dim picture As New SqlParameter("#picture", pictureFileUpload.FileBytes)
Dim id As New SqlParameter("#id", t_id)
myCommand = New SqlCommand("spChangeImage")
myCommand.CommandType = CommandType.StoredProcedure
myCommand.Connection = conn
myCommand.Parameters.Add(picture)
myCommand.Parameters.Add(id)
myCommand.ExecuteNonQuery()
close()
Now I need a way to open an image file and set it as a parameter in a similar manner, but I've no clue as to how to go about doing that. All the search results are focused on opening and viewing an image in html, I just need the binary to use it in the query. I'm trying to use binaryreader but even then I've no idea how to actually map the file to begin with.
Thanks in advance for any help!
Personally, I wouldn't store this image in the database when the user deletes their value. I would set the column to null. When writing the image I would detect if the column is null, then read the file and write it to the response. If you do this, then you won't need to accumulate anything into a local buffer, you can just write each buffer to the response as it is read. You can use FileInfo.Length to determine the content length of the response.
If you insist on putting the image in the DB, you can also use FileInfo.Length to determine the size of buffer you need to hold the image. Use your BinaryReader to read this length of bytes into the buffer. The buffer then becomes your parameter to the SQL command.
this might help.
How can I export the data in my webapp to an Excel sheet from ASP.NET (VB.NET,SQL 2005)?
change the contenttype of your ASP.Net page
Response.ContentType = "application/ms-excel"
One of my most popular blogs is how to generate an Excel document from .NET code, using the Excel XML markup (this is not OpenXML, it's standard Excel XML) - http://www.aaron-powell.com/linq-to-xml-to-excel
I also link off to an easier way to do it with VB 9.
Although this is .NET 3.5 code it could easily be done in .NET 2.0 using XmlDocument and creating the nodes that way.
Then it's just a matter to set the right response headers and streaming back in the response.
SpreadsheetGear for .NET will do it. You can find a bunch of live ASP.NET samples with C# & VB.NET source on this page.
Disclaimer: I own SpreadsheetGear LLC
If you can display your data in a GridView control, it inherently supports "right-click-->Export to Excel" without having to write any code whatsoever.
SQL Server Reporting services would be the best way to export data from an application into Excel.
If you dont have access to / dont wan't to use reporting services depending on the data you want to extract / format possibly using a CSV structure instead of Excel may be easiest.
Use the Microsoft.Office.Interop.Excel dlls to create excel files with your data and then provide links to download the files using Hunter Daley's download method...
As a general solution, you may want to consider writing handler (ashx) for exporting -- and pass either the query parameters to recreate the query to generate the data or an identifier to get the data from the cache (if cached). Depending on whether CSV is sufficient for your Excel export you could just format the data and send it back, setting the ContentType as #Hunter suggests or use the primary interop assemblies (which would require Excel on the server) to construct a real Excel spreadsheet and serialize it to the response stream.
I prefer to use a OLEDB connection string.
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Excel.xls;Extended Properties="Excel 8.0;HDR=Yes;IMEX=1";
Not sure about exporting a page but if you just want to export a dataset or datatable
HttpContext.Current.Response.Clear()
HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fileName))
HttpContext.Current.Response.ContentType = "application/ms-excel"
Dim sw As StringWriter = New StringWriter
Dim htw As HtmlTextWriter = New HtmlTextWriter(sw)
Dim table As Table = New Table
table.RenderControl(htw)
' render the htmlwriter into the response
HttpContext.Current.Response.Write(sw.ToString)
HttpContext.Current.Response.End()
I use almost the same exact code as CodeKiwi. I would use that if you have a DataTable and want to stream it to the client browser.
If you want a file, you could also do a simple loop through each row/column, create a CSV file and I guess provide a link to the client - you can use a file extension of CSV or XLS. Or if you stream the resulting file to the client it will prompt them if they want to open or save it to disk.
The interops are (well were last time I tried them) great for small datasets, but didn't scale well - horrifically slow for larger datasets.
Very odd problem as this is working perfectly on our old Classic ASP site. We are basically querying the database and exporting around 2200 lines of text to a Text File through Response.Write to be output to a dialog box and allows the user to save the file.
Response.Clear()
Response.ClearContent()
Response.ClearHeaders()
Dim fileName As String = "TECH" & test & ".txt"
Response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}", fileName))
Response.ContentType = "text/plain"
Response.Write(strHeader)
Dim sw As New IO.StringWriter()
Dim dtRow As DataRow
For Each dtRow In dt3.Rows
sw.Write(dtRow.Item("RECORD") & vbCrLf)
Next
Response.Write(sw.ToString)
Response.Write(strTrailer & intRecCount)
Response.End()
I can either use StringWriter or simply use Response.Write(dt.Rows(i).Item("RECORD").toString
Either way, the Export is causing a horrendous hang on our development site. My local machine causes no hang and is almost instantaneous. The recordset isn't very large, and the lines it is writing are small.
Anyone have any idea why this would be hanging? It does EVENTUALLY allow for a save and display the file, but it's well over 3-4 minutes.
Attach a remote debugger and find where its hanging?
You need to figure out if its the string writer loop, or the actual query code (which is not provided here).
Sounds like maybe you're overflowing the output buffer. Perhaps add a counter in there to flush every few hundred lines.
Also, the Response object basically does most of the work for a StringWriter for you. Using the StringWriter as an intermediary is probably redundant.
Both using StringWriter and DataTable are overkill.
Why not use directly SqlReader to get the results from the database, and while reading the reader, write directly to the output stream? Much faster, and much less memory consumed.
As an answer to your second question - why the ASP was working OK, I doubt that there you have stored the same content 3 times in memory in order to output it (in the DataTable, in the StringWriter and in the output buffer). My ASP is a little bit rusty, but I would guess that there you are using database reader of some sort.
Also, better employ some logging infrastructure (NLog, log4net), so you can output some timing about which operation delays how much, as an alternative to attaching a remote debugger.