Question

我使用通过数据集传递的XML Excel生成一个Excel报告。

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

当数据集计数为20000或更少时，它可以正常工作。

当数据集包含超过23000条记录时。

它正确调试，最后这个函数返回字符串语句，抛出错误为

System.OutofMemory异常。 c＃中也使用了相同的编码概念集。但它不会返回错误并正常工作。可以任何一个。请找出错误或告诉我正确的方法。

Answer 1

最后我以简单的方式解决了我的问题。

我希望你能回答这个问题。

我的场景我正在使用Stringwriter从数据集中编写数据。当我的数据集包含超过20000条记录时，它会抛出一个错误“System.outofmeory exception”。因为Stringwriter会将您的数据保存在虚拟内存（RAM）中。

所以，我使用的是Streamwriter而不是Stringwriter。

第1步：

我最初用标题创建了XML excel。

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()

第二步：

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

最后从您保存的位置获取文件。

stringwriter.tostring outofmemoryexception仅在vb.net中显示

1 个答案: