Question

对于Windows窗体应用程序没有太多经验（这是我第一次尝试构建），但是当我的应用程序不断在Form1_Load和7个Browsebutton_Click Subs中的2个上抛出空引用错误时，我无法理解。其他5个完美无缺。

其他信息：

我稍后在我的应用程序中添加的非工作按钮
在Form1_Load上并单击2个非工作浏览按钮返回相同的错误：System.NullreferenceException：“Object 引用未设置为对象的实例“
在VS中测试应用程序时，一切都很好在我构建解决方案后，安装它并在我的计算机上运行它出现错误

AppConfig文件appsettings-part看起来像这样（验证所有路径并确实存在）：

<appSettings>
<add key="LastZHRverzamelPDF" value="C:\x\pdf files\TestPDF.pdf" />
<add key="LastMapSplitted" value="C:\x\pdf files\ZHRFORMS" />
<add key="LastPersFile" value="C:\x\pdf files\Personeelslijst.xlsx" />
<add key="LastMap1" value="C:\x\pdf files\Salarisslips" />
<add key="LastMap2" value="C:\x\pdf files\Vakantie-uren" />
<add key="LastMap3" value="C:\x\pdf files\ZHRFORMS" />
<add key="LastMap4" value="C:\x\pdf files\Logitime" />
<add key="ClientSettingsProvider.ServiceUri" value="" />
</appSettings>

Form1_Load过程包含以下代码：

Private Sub Form1_Load(sender As System.Object, e As EventArgs) Handles MyBase.Load
    Try

        'Laatstgekozen waarden uit app.config halen en in lbls neerzetten
        lblZHRFile.Text = ConfigurationManager.AppSettings("LastZHRverzamelPDF").ToString()
        lblMapSplitted.Text = ConfigurationManager.AppSettings("LastMapSplitted").ToString() & "\"

        lblPersFile.Text = ConfigurationManager.AppSettings("LastPersFile").ToString()
        lblMap1.Text = ConfigurationManager.AppSettings("LastMap1").ToString() & "\"
        lblMap2.Text = ConfigurationManager.AppSettings("LastMap2").ToString() & "\"
        lblMap3.Text = ConfigurationManager.AppSettings("LastMap3").ToString() & "\"
        lblMap4.Text = ConfigurationManager.AppSettings("LastMap4").ToString() & "\"

    Catch ex As Exception
        Dim exMsg As String = "Message: " & ex.Message & vbCrLf & "Source: " & ex.Source & vbCrLf & "StackTrace: " & ex.StackTrace
        MsgBox(exMsg, MsgBoxStyle.Information, "Sub Form1_Load")
        Dim errormsg As String = ex.Message

    End Try

End Sub

我在这里将appconfig值加载到UserForm标签中以显示最后选择的值。在7个标签旁边，我有7个浏览按钮来修改路径。不工作的其中两个包含以下代码：

Private Sub btnZHRPath_Click(sender As Object, e As EventArgs) Handles btnZHRPath.Click
    Try
        Dim fd As OpenFileDialog = New OpenFileDialog()
        fd.FileName = ConfigurationManager.AppSettings("LastZHRverzamelPDF").ToString()
        Dim strFileName As String

        With fd
            .Title = "Selecteer verzamel-PDF file ZHRFORMS uit SAP"
            .InitialDirectory = ""
            .Filter = "All files (*.pdf)|*.pdf|All files (*.pdf)|*.pdf"
            .FilterIndex = 2
            .RestoreDirectory = True
        End With
        If fd.ShowDialog() = DialogResult.OK Then
            strFileName = fd.FileName
            lblZHRFile.Text = strFileName
            Dim objConfig As Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
            objConfig.AppSettings.Settings("LastZHRverzamelPDF").Value = strFileName
            objConfig.Save(ConfigurationSaveMode.Modified)
            ConfigurationManager.RefreshSection("appSettings")
        Else
            lblZHRFile.Text = "(overslaan)"
        End If
    Catch ex As Exception
        Dim exMsg As String = "Message: " & ex.Message & vbCrLf & "Source: " & ex.Source & vbCrLf & "StackTrace: " & ex.StackTrace
        MsgBox(exMsg, MsgBoxStyle.Information, "btnZHRPath_Click")

    End Try
End Sub

同样的原因也不起作用：

 Private Sub btnSplittedPath_Click(sender As Object, e As EventArgs) Handles btnSplittedPath.Click

    Try
        If sender = Nothing Then MsgBox("nullsender")
        lblMapSplitted.Text = "C:\" 'ConfigurationManager.AppSettings("LastMapSplitted").ToString() & "\"

        Dim Map As FolderBrowserDialog = New FolderBrowserDialog
        Map.SelectedPath = ConfigurationManager.AppSettings("LastMapSplitted").ToString()
        Map.Description = "Selecteer doelmap voor gesplitte PDF-files"
        Map.ShowNewFolderButton = True
        Dim DoelMap As String = ""
        If Map.ShowDialog() = Windows.Forms.DialogResult.OK Then
            DoelMap = Map.SelectedPath & "\"
            Dim objConfig As Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
            objConfig.AppSettings.Settings("LastMapSplitted").Value = Map.SelectedPath
            objConfig.Save(ConfigurationSaveMode.Modified)
            ConfigurationManager.RefreshSection("appSettings")
        Else
            DoelMap = "(overslaan)"
        End If
        lblMapSplitted.Text = DoelMap
    Catch ex As Exception
        Dim exMsg As String = "Message: " & ex.Message & vbCrLf & "Source: " & ex.Source & vbCrLf & "StackTrace: " & ex.StackTrace
        MsgBox(exMsg, MsgBoxStyle.Information, "btnSplittedPath_Click")

    End Try
End Sub

奇怪的是，这个浏览按钮正常工作（就像剩下的4个代码相似）：

Private Sub btnFilePath_Click(sender As Object, e As EventArgs) Handles btnFilePath.Click

    Dim fd As OpenFileDialog = New OpenFileDialog()
    Dim strFileName As String
    fd.FileName = ConfigurationManager.AppSettings("LastPersFile").ToString()
    With fd
        .Title = "Selecteer bestand met medewerkergegevens"
        .InitialDirectory = ""
        .Filter = "All files (*.xl*)|*.xl*|All files (*.xl*)|*.xl*"
        .FilterIndex = 2
        .RestoreDirectory = True
    End With
    If fd.ShowDialog() = DialogResult.OK Then
        strFileName = fd.FileName
        lblPersFile.Text = strFileName
        Dim objConfig As Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
        objConfig.AppSettings.Settings("LastPersFile").Value = strFileName
        objConfig.Save(ConfigurationSaveMode.Modified)
        ConfigurationManager.RefreshSection("appSettings")
    End If

End Sub

尝试了一切来解决这个问题，但根本无法弄清楚为什么我的应用程序不断向我抛出这些错误！请帮帮我吧！

VB.NET Form1_Load和Button_Click不断抛出Nullreference Error

0 个答案: