Download xls file to client from Datatable - excel

Question

I am developing a website on VisualStudio using VB. In one section of my site I make a DataBase Query, store the result in a DataTable and display it. I give the user the option of dowloading the information, what I would like to do is to download an XLS file to the client's side with the information in the datatable without creating the xls on the server side.
I currently have the following code section to send the file to the user
Dim fileToDownload = Server.MapPath("~/docs/QuejometroVF.pdf")
Response.ContentType = "application/octet-stream"
Dim cd = New ContentDisposition()
cd.Inline = False
cd.FileName = Path.GetFileName(fileToDownload)
Response.AppendHeader("Content-Disposition", cd.ToString())
Dim fileData = System.IO.File.ReadAllBytes(fileToDownload)
Response.OutputStream.Write(fileData, 0, fileData.Length)
But it requires a path to a local file in order to send it.
First I would like to know how to create a xls file from the datatable (only in memory) and then send that object as a file to the client's computer. If it is not possible, Could you tell me how to write the xls file in my server so I can then send it using the code above? I have not really figured out how to do it yet.
I was thinking on doint it that way because I don't want to keep files in the server when I already have that information on the database and I don't pretend on keeping that file stored.
Thank you

Answer 1

I export data to xls file using the following code, my backend is an Oracle database and that's where I get the data:
Dim MyConnection As OracleConnection = OpenConnection(Session("USERNAME"), Session("PASSWORD"))
Dim MyDataSet As New DataSet
MyDataSet = GetExportData(MyConnection, Session("UserDataKey"), Session("CompoundKey"), Session("LastOfCompoundKey"))
'I rename the dataset's table columns to what I want in the xls file
MyDataSet.Tables!data.Columns(0).ColumnName = "IDNumber"
MyDataSet.Tables!data.Columns(1).ColumnName = "FirstName"
MyDataSet.Tables!data.Columns(2).ColumnName = "LastName"
MyDataSet.Tables!data.Columns(3).ColumnName = "Address"
MyDataSet.Tables!data.Columns(4).ColumnName = "City"
MyDataSet.Tables!data.Columns(5).ColumnName = "State"
MyDataSet.Tables!data.Columns(6).ColumnName = "ZipCode"
MyDataSet.Tables!data.Columns(7).ColumnName = "Phone_Area"
MyDataSet.Tables!data.Columns(8).ColumnName = "Phone_Prefix"
MyDataSet.Tables!data.Columns(9).ColumnName = "Phone_Suffix"
MyDataSet.Tables!data.Columns(10).ColumnName = "Email"
MyDataSet.Tables!data.Columns(11).ColumnName = "BirthDay"
Response.ClearContent()
'I create the filename I want the data to be saved to and set up the response
Response.AddHeader("content-disposition", "attachment; filename=" & Replace(Session("Key0"), " ", "-") & "-" & Session("Key1") & "-" & Replace(Replace(Trim(Session("Key2")), ".", ""), " ", "-") & ".xls")
Response.ContentType = "application/excel"
Response.Charset = ""
EnableViewState = False
Dim tw As New System.IO.StringWriter
Dim hw As New System.Web.UI.HtmlTextWriter(tw)
'Create and bind table to a datagrid
Dim dgTableForExport As New DataGrid
If MyDataSet.Tables.Count > 0 Then
If MyDataSet.Tables(0).Rows.Count > 0 Then
dgTableForExport.DataSource = MyDataSet.Tables(0) ' .DefaultView
dgTableForExport.DataBind()
'Finish building response
Dim strStyle As String = "<style>.text { mso-number-format:\#; } </style>"
For intTemp As Integer = 0 To MyDataSet.Tables(0).Rows.Count - 1
For intTemp2 As Integer = 0 To MyDataSet.Tables(0).Columns.Count - 1
dgTableForExport.Items(intTemp).Cells(intTemp2).Attributes.Add("class", "text")
Next
Next
End If
End If
dgTableForExport.RenderControl(hw)
Response.Write(style)
' Write the HTML back to the browser.
Response.Write(tw.ToString())
Response.End()
'Close, clear and dispose
MyConnection.Close()
MyConnection.Dispose()
MyConnection = Nothing
I copied and pasted this from one of my projects, it's untested and may contain error but should get you started.

Answer 2

You can use a MemoryStream or to write the file to Response stream using Response.Write method.

Answer 3

Creating an excel file from a data table is fairly easy as you can just create a GridView and bind the table to it.
Here is a code snippet that does what you need.
Public Sub DownloadExcel(outputTable as System.Data.DataTable)
Dim gv As New GridView
Dim tw As New StringWriter
Dim hw As New HtmlTextWriter(tw)
Dim sheetName As String = "OutputFilenameHere"
gv.DataSource = outputTable
gv.DataBind()
gv.RenderControl(hw)
Response.AddHeader("content-disposition", "attachment; filename=" & sheetName & ".xls")
Response.ContentType = "application/octet-stream"
Response.Charset = ""
EnableViewState = False
Response.Write(tw.ToString)
Response.End()
End Sub
There are a few issues with this method:
This doesn't output a native excel file. Instead, it outputs the HTML for a GridView that Excel will detect and notify the user that the content doesn't match the extension. However, it WILL display in Excel correctly if the user selects 'Yes' from the dialog box.
Earlier versions of Firefox and Chrome didn't like this method and instead download the file with a .html extension. I just tested it in both browsers and it worked with the most up to date versions.
Ideally, you should probably use Excel on your webserver to create native spreadsheets, but this will work if you (like me) don't have the means to do so.