stringwriter.tostring outofmemoryexception shown only in vb.net

Question

I am generating one Excel report using XML Excel passing via dataset.

Private Function getWorksheets(source As DataSet) As String
            Dim dc As DataColumn
            Dim sw As StringWriter = New StringWriter()
            Dim sww As StringWriter = New StringWriter()
            Dim sheetCount As Integer = 0


            If (source Is Nothing Or source.Tables.Count = 0) Then
                sw.Write("<Worksheet ss:Name=""Sheet1"">" + "<Table>" + System.Environment.NewLine + System.Environment.NewLine + "<Row><Cell><Data ss:Type=""String""></Data></Cell></Row>" + System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
                Return sw.ToString()
            End If


            For Each dt As DataTable In source.Tables

                If (dt.Rows.Count = 0) Then

                    sw.Write("<Worksheet ss:Name=""" + replaceXmlChar(dt.TableName) + """>" + System.Environment.NewLine + System.Environment.NewLine + "<Table>" + System.Environment.NewLine + System.Environment.NewLine + "<Row><Cell ss:StyleID=""s62""><Data ss:Type=""String""></Data></Cell></Row>" + System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")

                Else
                    'write each row data 

                    For i As Integer = 0 To dt.Rows.Count - 1

                        If ((i Mod rowLimit) = 0) Then

                            'add close tags for previous sheet of the same data table 
                            If ((i / rowLimit) > sheetCount) Then

                                sw.Write(System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
                                sheetCount = (i / rowLimit)
                            End If
                            'sw.Write((System.Environment.NewLine + System.Environment.NewLine + "<Worksheet ss:Name=" + replaceXmlChar(dt.TableName)) + ((((i / rowLimit) = 0) ? """ : "_" + Convert.ToString(i / rowLimit))) + "\">" + System.Environment.NewLine + System.Environment.NewLine + "<Table>");

                            sw.Write((System.Environment.NewLine & System.Environment.NewLine & "<Worksheet ss:Name=""" & replaceXmlChar(dt.TableName)) & ((If(((i / rowLimit) = 0), "", "_" & Convert.ToString(i / rowLimit)))) & """>" & System.Environment.NewLine & System.Environment.NewLine & "<Table>")


                            'write column name row 
                            sw.Write(System.Environment.NewLine + System.Environment.NewLine + "<Row>")

                            For Each dc In dt.Columns

                                sw.Write(String.Format("<Cell ss:StyleID=""s62""><Data ss:Type=""String"">{0}</Data></Cell>", replaceXmlChar(dc.ColumnName)))
                            Next
                            sw.Write("</Row>")
                        End If

                        sw.Write(System.Environment.NewLine + System.Environment.NewLine + "<Row>")
                        For Each dc In dt.Columns
                            sw.Write(getCell(dc.DataType, dt.Rows(i)(dc.ColumnName)))
                        Next
                        sw.Write("</Row>")

                    Next
                    sw.Write(System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
                End If
            Next

            Return String.Format(sw.ToString())
End Function

it working properly when dataset count 20000 or less.

when dataset contain more than 23000 records.

it debugging properly and finally this function return string statement, thrown an error as

System.OutofMemory Exception. same set of coding concepts also used in c#. but it does not return an error and working properly. can any one. please find the mistake or tell me the correct way.

Answer 1

Finally i resolved my problem in Simple way.

I hope this answer will you.

My scenario i am writing data from dataset using Stringwriter. When my dataset contain more than 20000 records, it thrown an error as "System.outofmeory exception". Because Stringwriter keep your data in virtual memory(RAM).

so, i used Streamwriter instead of Stringwriter.

1st step:

I created XML excel with header initially.

Dim excelTemp As String = getWorkbookTemplate()
Dim fs As IO.FileStream
Dim sw As IO.StreamWriter
fs = New IO.FileStream(filename, IO.FileMode.Create, IO.FileAccess.Write)
sw = New IO.StreamWriter(fs)
sw.Write(excelTemp)  -- Here some header for excel files.
sw.Flush()
sw.Close()
fs.Close() --  file closed
getWorksheets(dsInput,filename)  -- calling getworksheet method with dataset and filename
fs.Close()

2nd step:

Private Sub getWorksheets(source As DataSet,fname As String)
        Dim dc As DataColumn
        Dim dr As DataRow
        Dim sw As StreamWriter = File.AppendText(fname)  -- Here my closed file again re-open and write to file directly using streamwriter Appendtext
        Dim sheetCount As Integer = 0

    If (source Is Nothing Or source.Tables.Count = 0) Then
        sw.Write("<Worksheet ss:Name=""Sheet1"">" + "<Table>" + System.Environment.NewLine + System.Environment.NewLine + "<Row><Cell><Data ss:Type=""String""></Data></Cell></Row>" + System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
    End If

    For Each dt As DataTable In source.Tables
        If (dt.Rows.Count = 0) Then
            sw.Write("<Worksheet ss:Name=""" + replaceXmlChar(dt.TableName) + """>" + System.Environment.NewLine + System.Environment.NewLine + "<Table>" + System.Environment.NewLine + System.Environment.NewLine + "<Row><Cell ss:StyleID=""s62""><Data ss:Type=""String""></Data></Cell></Row>" + System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
        Else
            'write each row data

            For i As Integer = 0 To dt.Rows.Count - 1
                If ((i Mod rowLimit) = 0) Then
                    'add close tags for previous sheet of the same data table

                    If ((i / rowLimit) > sheetCount) Then
                        sw.Write(System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
                        sheetCount = (i / rowLimit)
                    End If

                    sw.Write((System.Environment.NewLine + System.Environment.NewLine + "<Worksheet ss:Name=""" + replaceXmlChar(dt.TableName)) + ((If(((i / rowLimit) = 0), "", "_" + Convert.ToString(i / rowLimit)))) + """>" + System.Environment.NewLine + System.Environment.NewLine + "<Table>")


                    'write column name row
                    sw.Write(System.Environment.NewLine + System.Environment.NewLine + "<Row>")

                    For Each dc In dt.Columns
                        sw.Write(String.Format("<Cell ss:StyleID=""s62""><Data ss:Type=""String"">{0}</Data></Cell>", replaceXmlChar(dc.ColumnName)))
                    Next
                    sw.Write("</Row>")
                End If
                sw.Write(System.Environment.NewLine + System.Environment.NewLine + "<Row>")

                For Each dc In dt.Columns
                    sw.Write(getCell(dc.DataType, dt.Rows(i)(dc.ColumnName)))
                Next
                sw.Write("</Row>")
            Next
            sw.Write(System.Environment.NewLine + System.Environment.NewLine + "</Table>" + System.Environment.NewLine + System.Environment.NewLine + "</Worksheet>")
        End If
    Next
    sw.Write("</Workbook>")
    sw.Flush()
    sw.Close()
End Sub

Finally get the file from location where you have saved.