Question

我有关于DataReader仍然打开的错误但我发现如果我使用不同的查询/命令它可以正常工作

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所以问题是我的mycommand字符串，但这是我需要加载所需的数据，所以任何建议如何解决它？感谢

     Private Sub daily()
    Cursor = Cursors.WaitCursor()
        MySQLcon.ConnectionString = MySQLserver
        MySQLcon.Open()
        'strPath & "\" & txtName.Text & ".xlsx"
        Dim dte As String = cboDate1.Text
        Dim myCommand1 As New MySql.Data.MySqlClient.MySqlCommand
        Dim myadapter As New MySql.Data.MySqlClient.MySqlDataAdapter
        Dim mybuilder As New MySql.Data.MySqlClient.MySqlCommandBuilder
        Dim mydatatable As New DataTable
        Dim mydataset As New DataSet
        myCommand1.Connection = MySQLcon

        'myCommand1.CommandText = "SELECT  `" + dte + "`.`Users`,concat((`users`.`Last Name`),', ',(`users`.`First Name`)) as `Name`,'" + dte + "'  as Date,`" + dte + "`.`Activity`,`" + dte + "`.`Field1` as `Project Name`,`" + dte + "`.`Field2` as `Job Name` ," + _
        '    "SUM(`" + dte + "`.`Field4`) as `Records`, SUM(`" + dte + "`.`Field5`)as Pages," + _
        '    "ROUND(sum(TIME_TO_SEC(`" + dte + "`.`Elapsed Time`))/3600,2)as `Hours`," + _
        '    "'G' as `REGS/HR`," + _
        '    "'H' as `PGS/HR`" + _
        '    "FROM `" + dte + "`" + _
        '    "INNER JOIN `users`" + _
        '    "ON `" + dte + "`.`Users`=`users`.`Employee ID`" + _
        '    "Where `" + dte + "`.`Group` = 'DATA ENTRY' and `" + dte + "`.`Field1` <> 'OVER-BREAK 1' and `" + dte + "`.`Field1` <> 'OVER-BREAK 2'  and (`" + dte + "`.`Activity` = 'KE' or `" + dte + "`.`Activity` = 'CH' or `" + dte + "`.`Activity` = 'SJ' or `" + dte + "`.`Activity` = 'VE' or `" + dte + "`.`Activity` = 'MB' or `" + dte + "`.`Activity` = 'TD' or `" + dte + "`.`Activity` = 'LK'  or `" + dte + "`.`Activity` = 'PG')" + _
        '    "GROUP BY  `" + dte + "`.`Users`, `" + dte + "`.`Activity`, `" + dte + "`.`Field1`"

        myCommand1.CommandText = "SELECT  `MERGED DATAENTRY`.`Users`,concat((`users`.`Last Name`),', ',(`users`.`First Name`)) as `Name`,'" + cboDate1.Text & " - " & cboDate2.Text + "'  as Date,`MERGED DATAENTRY`.`Activity`,`MERGED DATAENTRY`.`Field1` as `Project Name`,`MERGED DATAENTRY`.`Field2` as `Job Name` ," + _
            "SUM(`MERGED DATAENTRY`.`Field4`) as `Records`, SUM(`MERGED DATAENTRY`.`Field5`)as Pages," + _
            "ROUND(sum(TIME_TO_SEC(`MERGED DATAENTRY`.`Elapsed Time`))/3600,2)as `Hours`," + _
            "'G' as `REGS/HR`," + _
            "'H' as `PGS/HR`" + _
            "FROM `MERGED DATAENTRY`" + _
            "INNER JOIN `users`" + _
            "ON `MERGED DATAENTRY`.`Users`=`users`.`Employee ID`" + _
            "Where `MERGED DATAENTRY`.`Group` = 'DATA ENTRY' and `MERGED DATAENTRY`.`Field1` <> 'OVER-BREAK 1' and `MERGED DATAENTRY`.`Field1` <> 'OVER-BREAK 2'  and (`MERGED DATAENTRY`.`Activity` = 'KE' or `MERGED DATAENTRY`.`Activity` = 'CH' or `MERGED DATAENTRY`.`Activity` = 'SJ' or `MERGED DATAENTRY`.`Activity` = 'VE' or `MERGED DATAENTRY`.`Activity` = 'MB' or `MERGED DATAENTRY`.`Activity` = 'TD' or `MERGED DATAENTRY`.`Activity` = 'LK'  or `MERGED DATAENTRY`.`Activity` = 'PG')" + _
            "GROUP BY  `MERGED DATAENTRY`.`Users`, `MERGED DATAENTRY`.`Activity`, `MERGED DATAENTRY`.`Field1`"
        myadapter.SelectCommand = myCommand1
        myadapter.Fill(mydataset)
        mydataset.Tables.Add(mydatatable)
        DataGridView1.DataSource = mydataset.Tables(0)

        Dim xlApp As Microsoft.Office.Interop.Excel.Application
        Dim xlWorkBook As Microsoft.Office.Interop.Excel.Workbook
        Dim xlWorkSheet As Microsoft.Office.Interop.Excel.Worksheet
        Dim misValue As Object = System.Reflection.Missing.Value


        Dim i As Integer
        Dim j As Integer

        xlApp = New Microsoft.Office.Interop.Excel.ApplicationClass
        xlWorkBook = xlApp.Workbooks.Add(misValue)
        xlWorkSheet = xlWorkBook.Sheets("sheet1")


        For i = 0 To DataGridView1.RowCount - 1
            For j = 0 To DataGridView1.ColumnCount - 1
                For k As Integer = 1 To DataGridView1.Columns.Count
                    'Dim style As Excel.Style = xlWorkSheet.Application.ActiveWorkbook.Styles.Add("NewStyle")
                    'style.Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Yellow)
                    'xlWorkSheet.Cells(1, k).Style = "NewStyle"
                    xlWorkSheet.Cells(1, k) = DataGridView1.Columns(k - 1).HeaderText
                    xlWorkSheet.Cells(i + 2, j + 1) = DataGridView1(j, i).Value.ToString()
                    If DataGridView1(j, i).ColumnIndex = 9 Then
                        xlWorkSheet.Cells(i + 2, j + 1) = "=ROUND(" & DataGridView1(j, i).Value.ToString() & (DataGridView1(j, i).RowIndex + 2) & "/" & "I" & (DataGridView1(j, i).RowIndex + 2) & ",2)"

                    End If
                    If DataGridView1(j, i).ColumnIndex = 10 Then
                        xlWorkSheet.Cells(i + 2, j + 1) = "=ROUND(" & DataGridView1(j, i).Value.ToString() & (DataGridView1(j, i).RowIndex + 2) & "/" & "I" & (DataGridView1(j, i).RowIndex + 2) & ",2)"

                    End If
                Next
            Next
        Next

        xlWorkSheet.SaveAs(strPath & "\" & txtName.Text & ".xlsx")
        xlWorkBook.Close()
        xlApp.Quit()
        ReleaseObject(xlApp)
        ReleaseObject(xlWorkBook)
        ReleaseObject(xlWorkSheet)
        MessageBox.Show("File Export Successfully!")
  MySQLcon.Close()

End Sub

Answer 1

MySqlDataAdapter是IDisposable，你没有处理它 MySQLcon和MySQLserver是在你发布的代码之外定义的，所以我在这里做了一些假设。

我认为这里有连接池，即每次运行时确实都不会获得新的数据库连接。因为当你在第二次或之后的时间点击这段代码时你没有处理你的MySqlDataAdapter等，你仍然可以打开＆＃39;查询＆＃39;与DB。

你需要检查所有的IDisposable：

Dim myCommand1 As New MySql.Data.MySqlClient.MySqlCommand
Dim myadapter As New MySql.Data.MySqlClient.MySqlDataAdapter
Dim mybuilder As New MySql.Data.MySqlClient.MySqlCommandBuilder
.....

并更改为使用陈述，即：

Using myadapter As New MySql.Data.MySqlClient.MySqlDataAdapter
    Using myCommand1 As New MySql.Data.MySqlClient.MySqlCommand
        Using mybuilder As New MySql.Data.MySqlClient.MySqlCommandBuilder
        .....
        End Using
    End Using
End Using

虽然我怀疑DataAdaptor是唯一真正重要的。

尝试阅读IDisposable

NB mydataset.Tables.Add（mydatatable）看起来毫无意义，你要在已经填充的数据集中添加一个空白表

由于我的查询，DataReader仍处于打开状态

1 个答案: