从Web访问配置文件 - 没有AppSettings

Question

我正在开发一个项目，要求我修改我写的Windows服务（用ASP.NET编写）的.config文件。需要从我正在开发的管理网站进行更改。当用户选择Web应用程序上的“更新”按钮时，将执行以下代码：

Protected Sub ModifyAppConfig()
        Try
            Dim configFile = "C:\App\App.exe.config"
            Dim configFileMap As New ExeConfigurationFileMap
            configFileMap.ExeConfigFilename = configFile
            Dim config As System.Configuration.Configuration
            config = ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None)
            config.AppSettings.Settings("LogDirectory").Value = txtLogDirectory.Text '* EXCEPTION IS THROWN HERE *
            config.Save()
        Catch ex As Exception

        End Try
    End Sub

当应用程序尝试访问“LogDirectory”AppSettings索引时，将引发异常。 Object reference not set to an instance of an object.在调试期间，AppSettings.Count = 0。为什么没有导入任何AppSettings？

我知道它正确打开文件，因为有ConnectionString数据。以下是配置文件：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <connectionStrings>
      <add name="conn" connectionString="Data Source=DBASE;Initial Catalog=NGDevl;Integrated Security=True" providerName="System.Data.SqlClient"/>
    </connectionStrings>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
    </startup>
    <appSettings>
      <add key="LogDirectory" value="C:\CTemp\"/>
    </appSettings>
</configuration>

如何访问和修改AppSettings（“LogDirectory”）值？

Answer 1

坦率地说，我认为你的程序没有任何问题。

我已经创建了一个VB.Net/Console模式MCVE，可以帮助您排除故障

Module1.vb中

Imports System.Configuration

'
' EXAMPLE OUTPUT:
'   Reading config file(test.exe.config)...
'   config.AppSettings.Settings("LogDirectory") : C : \CTemp\
'   connectionStrings: <connectionStrings>
'   <add name = "conn" connectionString="Data Source=DBASE;Initial Catalog=NGDevl;
'   Integrated Security=True" providerName="System.Data.SqlClient"/>
'     </connectionStrings>
'   appSettings: <appSettings>
'   <add key = "LogDirectory" value="C:\CTemp\"/>
'     </appSettings>
'   startup: <startup>
'   <supportedRuntime version = "v4.0" sku=".NETFramework,Version=v4.5"/>
'     </startup>
'   3 sections were found.
'
Module Module1

    Sub Main()
        ' Get filename
        Dim args() As String = System.Environment.GetCommandLineArgs()
        If args.Length <> 2 Then
            Console.WriteLine("USAGE: ReadAppConfig <\path\to\app.config>")
            Return
        End If
        Dim configFilePath As String = args(1)

        ' Open config file
        Try
            Console.WriteLine("Reading config file(" & configFilePath & ")...")
            Dim configFileMap As New ExeConfigurationFileMap
            configFileMap.ExeConfigFilename = configFilePath
            Dim config As System.Configuration.Configuration
            config = ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None)

            ' Try to read AppSettings["LogDirectory"]
            Dim obj = config.AppSettings.Settings("LogDirectory")
            If IsNothing(obj) Then
                Console.WriteLine("config.AppSettings.Settings(""LogDirectory""): NULL")
            Else
                Console.WriteLine("config.AppSettings.Settings(""LogDirectory""): " & obj.Value)
            End If

            ' Dump all Sections
            Dim ct As Integer = 0
            For Each section As ConfigurationSection In config.Sections
                Dim xml = section.SectionInformation.GetRawXml
                If Not xml = Nothing Then
                    Console.WriteLine(section.SectionInformation.Name & ": " & xml)
                    ct = ct + 1
                End If
            Next
            Console.WriteLine(ct & " sections were found.")
        Catch ex As Exception
            System.Console.WriteLine("ERROR:   " & ex.Message)
        End Try

    End Sub

End Module

test.exe.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="conn" connectionString="Data Source=DBASE;Initial Catalog=NGDevl;Integrated Security=True" providerName="System.Data.SqlClient"/>
  </connectionStrings>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
  </startup>
  <appSettings>
    <add key="LogDirectory" value="C:\CTemp\"/>
  </appSettings>
</configuration>

• Project> test.exe.config：我将“Copy to Output”属性设置为“Copy if Newer”
• 项目>属性>调试：我将“命令行参数”设置为“test.exe.config”

'希望有帮助......