I have a sub that exports a ASP Gridview to excel, it works fine, however, when there are a large amount of rows I get this error:
Exception of type 'System.OutOfMemoryException' was thrown.
Any ideas how to solve this? Here is my export to excel sub:
Protected Sub btnExportMonthlyUK_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnExportMonth.Click
Dim title As String
title = "MonthlyReportUK"
Response.Clear()
Response.AddHeader("content-disposition", String.Format("attachment;filename={0}.xls", title))
Response.Charset = ""
Response.ContentType = "application/vnd.xls"
Response.ContentEncoding = Encoding.Unicode
Response.BinaryWrite(Encoding.Unicode.GetPreamble())
Dim strWr As New StringWriter()
Dim HtmlWr As New HtmlTextWriter(strWr)
monthlyReportsIE.AllowPaging = False
monthlyReportsIE.DataBind()
monthlyReportsIE.RenderControl(HtmlWr)
Response.Write(strWr.ToString())
Response.End()
End Sub
You can try rendering the control directly to the output stream by using a StreamWriter and avoid creating a large string in memory. You can also try setting Response.Buffer to False and the server will send the output to the client directly as it is processed.
Protected Sub btnExportMonthlyUK_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnExportMonth.Click
Dim title As String
title = "MonthlyReportUK"
Response.Clear()
Response.AddHeader("content-disposition", String.Format("attachment;filename={0}.xls", title))
Response.Charset = ""
Response.ContentType = "application/vnd.xls"
Response.ContentEncoding = Encoding.Unicode
Response.BinaryWrite(Encoding.Unicode.GetPreamble())
Response.Buffer = False
monthlyReportsIE.AllowPaging = False
monthlyReportsIE.DataBind()
Using strWr As new StreamWriter(response.OutputStream)
Using htmlWr As new HtmlTextWriter(strWr)
monthlyReportsIE.RenderControl(htmlWr)
End Using
End Using
Response.End()
End Sub
If this answer is not valid in your case, then you should consider an external library to do the job, because exporting large Excel files as HTML is memory consuming.
Check this sample about how to export the datatable of gridview.
Related
The following code is my current attempt at opening some data in excel from a website button in VB.Net. I would like the data to show up barebones, but the formatting from the table on the website always follows. The paging and colors make the data near impossible to read and can only see the first page of data. Any quick fixes? I've tried a lot of things I've found on here but to no avail.
Private Sub DownloadExcel()
Response.Clear()
'Dim dt As DataTable = TryCast(ViewState("GridData"), DataTable)
Grid_Bad_Meters.AllowPaging = False
Grid_Bad_Meters.AllowSorting = False
'Grid_Bad_Meters.DataSource = dt
'Grid_Bad_Meters.DataBind()
Dim sfile As String = "Communication_Failures" & Now.Ticks
Response.AddHeader("content-disposition", "attachment;filename=" & sfile & ".xls")
Response.Charset = ""
' If you want the option to open the Excel file without saving then
' comment out the line below
' Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.ContentType = "application/vnd.ms-excel"
Dim stringWrite As New System.IO.StringWriter()
Dim htmlWrite As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(stringWrite)
Grid_Bad_Meters.RenderControl(htmlWrite)
Response.Write(stringWrite.ToString())
Response.End()
'Grid_Bad_Meters.AllowPaging = True
'Grid_Bad_Meters.AllowSorting = True
'GridView1.DataSource = dt
'GridView1.DataBind()
End Sub
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Try
Dim ScriptManager As ScriptManager = ScriptManager.GetCurrent(Me.Page)
ScriptManager.RegisterPostBackControl(Me.btnExportToExcel)
Catch ex As Exception
End Try
End Sub
Protected Sub btnExportToExcel_Click(sender As Object, e As EventArgs) Handles btnExportToExcel.Click
Try
Dim sw As New System.IO.StringWriter()
Dim hw As New System.Web.UI.HtmlTextWriter(sw)
Dim style As String = "<style>.textmode{mso-number-format:\#;}</style>"
Response.Clear()
Response.Buffer = True
Response.AddHeader("content-disposition", "attachment;filename=SignExport.xls")
Response.Charset = ""
Response.ContentType = "application/vnd.ms-excel"
For i As Integer = 0 To Me.Grid_Bad_Meters.Rows.Count - 1
Dim row As GridViewRow = Grid_Bad_Meters.Rows(i)
row.Attributes.Add("class", "textmode")
Next
'lblRptHeader.RenderControl(hw)
hw.WriteBreak()
'lblReportDateRange.RenderControl(hw)
Grid_Bad_Meters.RenderControl(hw)
Response.Write(style)
Response.Output.Write(sw.ToString())
Response.Flush()
Response.End()
Catch ex As Exception
End Try
End Sub
You could use one of the two approaches mentioned below. Of course, there are other ways of meeting your requirement like exporting to csv file as mentioned in a comment or using a .Net library meant for Excel exporting like epplus.
OpenXML Approach
If you are looking for a way to export to Excel without using the html approach, then you can use OpenXML approach that is explained very clearly with a working example at this URL: Export to Excel using OpenXML. This will eliminate all the CSS styles that can get associated with exporting using html approach and you seem to be using this html approach according to the code in your original post. However, if you want to use the html approach, then the code below should work and eliminate all CSS styles that can come in the way when viewing the excel file. I have actually tried this posted code on my machine before putting it here.
Html Approach
You can create a new instance of GridView in your export method rather than use an existing instance, and data bind it to same data as the existing gridview on your page before rendering it to excel. Before you data bind it in the export method you need to make sure that no styles are set and specifically the grid line are set to none as in code below.
You can see an actual video of how this works at this URL : Grid Export without any CSS Styles. This was how the code behaved on my laptop when I ran it.
You can use sample code below, but make sure the data source is set to data that includes all records across all pages of original gridview. I have used SqlDataSource1 as data source but you can replace it by an appropriate method in your situation.
Protected Sub btnExport_Click(sender As Object, e As EventArgs)
Dim GridView2 As New GridView()
GridView2.AllowPaging = False
GridView2.AllowSorting = False
GridView2.Style.Clear()
GridView2.CellPadding = 0
GridView2.CellSpacing = 0
GridView2.GridLines = GridLines.None
GridView2.BorderStyle = BorderStyle.None
GridView2.BorderWidth = Unit.Pixel(0)
GridView2.AlternatingRowStyle.BorderStyle = BorderStyle.None
GridView2.DataSource = SqlDataSource1
GridView2.DataBind()
' Clear the response
Response.Clear()
' Set the type and filename
Response.AddHeader("content-disposition", "attachment;filename=griddata.xls")
Response.Charset = ""
Response.ContentType = "application/vnd.xls"
' Add the HTML from the GridView to a StringWriter so we can write it out later
Dim sw As New System.IO.StringWriter()
Dim hw As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(sw)
GridView2.RenderControl(hw)
' Write out the data
Response.Write(sw.ToString())
Response.[End]()
End Sub
Public Overrides Property EnableEventValidation() As Boolean
Get
Return False
End Get
'Do nothing
Set
End Set
End Property
Public Overrides Sub VerifyRenderingInServerForm(control As Control)
'Allows for printing
End Sub
The code I'm troubleshooting exports a Crystal Report ReportDocument to Excel. Most of the time, the export works just fine. Unfortunately for some datasets, the ExportToHttpResponse method never returns and causes the app to hang. Eventually there is a Thread was being aborted exception along with a request timeout.
Here is the line that hangs:
reportDocument.ExportToHttpResponse(ExportFormatType.Excel,Response,True, fileName);
I also tried using ExportToStream from here which also hangs:
System.IO.Stream myStream;
byte[] byteArray;
myStream = boReportDocument.ExportToStream (ExportFormatType.PortableDocFormat);
I have tried different export formats, restarting IIS, etc. There seems to be a size limit or perhaps specific data scenarios that cause these methods to hang. Any workarounds or explanations for this behavior? Thanks!
Try this:
Public Shared Sub ExportDataSetToExcel(ByVal ds As DataTable, ByVal filename As String)
Dim response As HttpResponse = HttpContext.Current.Response
response.Clear()
response.Buffer = True
response.Charset = ""
'response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
response.ContentType = "application/vnd.ms-excel"
'response.AddHeader("Content-Disposition", "attachment;filename=""" & filename & ".xls")
Using sw As New StringWriter()
Using htw As New HtmlTextWriter(sw)
Dim dg As New DataGrid()
dg.DataSource = ds
dg.DataBind()
dg.RenderControl(htw)
response.Charset = "UTF-8"
response.ContentEncoding = System.Text.Encoding.UTF8
response.BinaryWrite(System.Text.Encoding.UTF8.GetPreamble())
response.Output.Write(sw.ToString())
response.[End]()
End Using
End Using
End Sub
and in your viewer add :
DT = New DataTable
DT = (Your Method)
ExportDataSetToExcel(DT, "ExportedReport")
also add :
Protected Sub Page_Unload(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Unload
ReportObject.Close()
ReportObject.Dispose()
End Sub
So report would not add restrictions on the number of loaded reports.
I have a GridView that I need to export into Excel (by button event) and I'm using Visual Studio and vb.net.
I never tried this before and I'm kinda clueless, is there a simple way to do this? I don't think I need any complications at the moment, just a simple export of the GridView information.
Also I already got a connection between the GridView and my database. I tried adding a working Excel export from other project but I still miss something .
Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
' Verifies that the control is rendered
End Sub
Protected Sub exportExelBtn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles exportExelBtn.Click
Dim errorCheck As Integer = 0
Dim popupscript As String = ""
If approvalGrid.Rows.Count > 0 Then
Try
Response.ClearContent()
Response.Buffer = True
Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", "TestPage.xls"))
Response.ContentEncoding = Encoding.UTF8
Response.ContentType = "application/ms-excel"
' Dim sw As New stringwriter()
Dim tw As New IO.StringWriter()
Dim htw As New HtmlTextWriter(tw)
approvalGrid.RenderControl(htw)
Response.Write(tw.ToString())
Response.[End]()
Catch ex As Exception
errorCheck = 1
End Try
Else
errorCheck = 1
End If
If errorCheck = 1 Then
'a pop up error messege feature
popupscript = "<script language='javascript'>" + "alert(" + Chr(34) + "There was an error in exporting to exel, please make sure there is a grid to export!" + Chr(34) + ");</script>"
End If
Page.ClientScript.RegisterStartupScript(Me.GetType(), "PopUpWindow", popupscript, False)
End Sub
The problem is that the file that it creates upon click says it's not Excel format and when I agree to open it I do see the GridView information as I wanted but I also see a lot of extra info in the form of buttons calanders and other stuff from my page, how can I prevent the export of those other stuff?
Please Try Below code
Public Overrides Sub VerifyRenderingInServerForm(control As Control)
' Verifies that the control is rendered
End Sub
Protected Sub btnExport_Click(sender As Object, e As EventArgs)
If gridview.Rows.Count > 0 Then
Try
gridview.Columns(0).Visible = False
Response.ClearContent()
Response.Buffer = True
Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", "TestPage.xls"))
Response.ContentEncoding = Encoding.UTF8
Response.ContentType = "application/ms-excel"
Dim sw As New StringWriter()
Dim htw As New HtmlTextWriter(sw)
gridview.RenderControl(htw)
Response.Write(sw.ToString())
Response.[End]()
Catch ex As Exception
Finally
gridview.Columns(0).Visible = True
End Try
End If
End Sub
I have written above code to export gridview to excel file, it exports successfully but there are some content in gridview in Persian language which is shown unreadable in exported excel file. the code I have written is as below:
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If GridView1.Rows.Count > 0 Then
Response.ClearContent()
Response.Buffer = True
Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", "IncentiveReport.xls"))
Response.ContentEncoding = Encoding.UTF8
Response.ContentType = "application/ms-excel"
Dim sw As New IO.StringWriter()
Dim htw As New HtmlTextWriter(sw)
GridView1.RenderControl(htw)
Response.Write(sw.ToString())
Response.End()
End If
End Sub
Public Overrides Sub VerifyRenderingInServerForm(control As Control)
' Verifies that the control is rendered
End Sub
i am getting error A generic error occurred in GDI+
on line
bit.Save(str, Imaging.ImageFormat.Png)
please help me on this here is my full code
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If IsNothing(Request.QueryString("id")) = False Then
If Val(Request.QueryString("id")) > 0 Then
Dim dsFiles As New DataSet
dsFiles = oFileData.GetFile(Val(Request.QueryString("id")))
Dim bindata() As Byte = dsFiles.Tables(0).Rows(0).Item("FileData")
Dim str As New MemoryStream
str.Write(bindata, 0, dsFiles.Tables(0).Rows(0).Item("FileSize"))
Dim bit As Bitmap = New Bitmap(str)
Response.ContentType = ".png"
bit.Save(str, Imaging.ImageFormat.Png)
str.WriteTo(Response.OutputStream)
str.Close()
Else
Response.Write("<script language=""javascript"" type=""text/javascript"">window.close();</script>")
End If
Else
Response.Write("<script language=""javascript"" type=""text/javascript"">window.close();</script>")
End If
End Sub
There may be many reasons - may be the content of byte array is not valid image data. In fact no need to create Bitmap or MemoryStream to write image data/bytes to response stream.
Try this,
Dim bindata() As Byte = dsFiles.Tables(0).Rows(0).Item("FileData")
Response.ContentType = "image/png"
Response.BinaryWrite(bindata)
Response.Flush()
Response.End()
I am able to export a gridview to excel, my problem is that I cannot figure out how to remove the formatting from coming over from the girdview. Here is the code I am using to export the gridview:
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Response.Clear()
Response.Charset = ""
'Response.ContentType = "application/vnd.ms-excel"
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
Dim stringWrite = New System.IO.StringWriter()
Dim htmlWrite As New System.Web.UI.HtmlTextWriter(stringWrite)
GridView1.GridLines = GridLines.None
GridView1.HeaderStyle.Font.Bold = True
GridView1.DataSourceID = SqlDataSource1.ID
GridView1.DataBind()
GridView1.RenderControl(htmlWrite)
Response.Write(stringWrite.ToString)
Response.End()
End Sub
What I suggest that you should iterate datasource , append the content of each row into StringBuilder object and write that string to the response buffer.