Question

im尝试将数据表导出到vb.net中的.csv文件。Ive编写的代码打开了一个保存文件对话框，并成功保存了.csv文件，但该文件为0字节且不包含任何数据。我正在使用MySQL数据库，数据库名称为“ tickedoff”，而我要导出的表为“ pet”。如果有人能看到我的代码中的错误并为我提供帮助，将不胜感激。.目前我完全感到沮丧。

此代码在Form1中（按钮单击事件）：

Private Sub btnPetInfoExport_Click(sender As Object, e As EventArgs) Handles btnPetInfoExport.Click
    Dim saveFileDialog1 = New SaveFileDialog()
    Dim statement As String = "SELECT pet.petID, pet.petName, pet.species, pet.breed, " _
                              & "pet.DOB, pet.gender, pet.weight," _
                              & "CONCAT(customer.lastName, ', ', customer.firstName) AS Customer " _
                              & "FROM pet INNER JOIN customer ON pet.customerID = customer.customerID " _
                              & "ORDER BY pet.petID"
    Dim petDataTable As DataTable =
            DataAccessLayer.GetPetDataTableForExport(statement)
    Dim saveFile As StreamWriter
    Dim fileName As String = String.Empty
    Dim csvBuilder As New StringBuilder()
    For i = 0 To petDataTable.Columns.Count - 1
        csvBuilder.Append(petDataTable.Columns(i).ColumnName + ","c)
    Next
    csvBuilder.Append(vbCr & vbLf)
    For i = 0 To petDataTable.Rows.Count - 1
        For o = 0 To petDataTable.Columns.Count - 1
            csvBuilder.Append(petDataTable.Rows(i)(o).ToString().Replace(",", ";") + ","c)
        Next
        csvBuilder.Append(vbCr & vbLf)
    Next
    saveFileDialog1.Filter = "CSV files ( .csv)|.csv|ALL files (.)|. "
    If saveFileDialog1.ShowDialog = System.Windows.Forms.DialogResult.OK Then
        fileName = saveFileDialog1.FileName
        Try
            saveFile = File.CreateText(fileName)
        Catch ex As Exception
            Throw ex
        End Try
    End If
End Sub

此函数从上面的子函数中调用，并且在一个单独的类中，称为“数据访问层”：

Public Shared Function GetPetDataTableForExport(statement As String) As 
    DataTable
    Dim petDataTableCommand As New MySqlCommand(statement)
    Dim petDataTable As New DataTable()
    Dim connection As New MySqlConnection("server=localhost; Port=3306; database=tickedoff; username=root;")
    Dim petDataTableAdapter As MySqlDataAdapter = New MySqlDataAdapter
    petDataTableCommand.CommandType = CommandType.Text
    petDataTableCommand.Connection = connection
    Try
        connection.Open()
        petDataTableAdapter.SelectCommand = petDataTableCommand
        'fill the table with the pet data from the database
        petDataTableAdapter.Fill(petDataTable)
    Catch ex As Exception
        Throw ex
    Finally
        connection.Close()
        petDataTableAdapter.Dispose()
        connection.Dispose()
    End Try
    Return petDataTable
End Function

如何使用MySQL修复从vb.net导出的空.csv文件？

0 个答案: