错误：尝试获取LogWriter类型的实例时出现激活错误，键“”

Question

在发布之前，我确实在这个论坛上搜索了这个错误并尝试了很多东西，但似乎没有任何工作，这是令人沮丧的。我的WCF服务app.config具有以下内容。请建议

    <?xml version="1.0" encoding="utf-8" ?>
<configuration>  
  <configSections>
    <section name="loggingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.LoggingSettings, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
    <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />
  </configSections>
  <loggingConfiguration name="" tracingEnabled="true" defaultCategory="Normal">
    <listeners>
      <add name="Event Log Listener" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.FormattedEventLogTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.FormattedEventLogTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        source="BackOffice" formatter="Text Formatter" log="IndexBackOffice"
        machineName="." traceOutputOptions="None" />
      <add name="Database Trace Listener" type="Microsoft.Practices.EnterpriseLibrary.Logging.Database.FormattedDatabaseTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging.Database, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Database.Configuration.FormattedDatabaseTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging.Database, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        databaseInstanceName="Connection.String" writeLogStoredProcName="WriteLog"
        addCategoryStoredProcName="AddCategory" />
      <add name="FlatFileTraceListener" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.FlatFileTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.FlatFileTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        fileName="trace.log" formatter="Text Formatter" />
    </listeners>
    <formatters>
      <add type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
        template="Timestamp: {timestamp}{newline}&#xA;Message: {message}{newline}&#xA;Category: {category}{newline}&#xA;Priority: {priority}{newline}&#xA;EventId: {eventid}{newline}&#xA;Severity: {severity}{newline}&#xA;Title:{title}{newline}&#xA;Machine: {localMachine}{newline}&#xA;App Domain: {localAppDomain}{newline}&#xA;ProcessId: {localProcessId}{newline}&#xA;Process Name: {localProcessName}{newline}&#xA;Thread Name: {threadName}{newline}&#xA;Win32 ThreadId:{win32ThreadId}{newline}&#xA;Extended Properties: {dictionary({key} - {value}{newline})}"
        name="Text Formatter" />
    </formatters>
    <categorySources>
      <add switchValue="All" name="Normal">
        <listeners>
          <add name="Event Log Listener" />
          <add name="Database Trace Listener" />
        </listeners>
      </add>
    </categorySources>
    <specialSources>
      <allEvents switchValue="All" name="All Events" />
      <notProcessed switchValue="All" name="Unprocessed Category" />
      <errors switchValue="All" name="Logging Errors &amp; Warnings">
        <listeners>
          <add name="Event Log Listener" />
        </listeners>
      </errors>
    </specialSources>
  </loggingConfiguration>
  <dataConfiguration defaultDatabase="DB" />
  <connectionStrings>       
      <add name="Connection.String" connectionString="Data Source=localhost;Initial Catalog=DB;Integrated Security=True;Connection Timeout=700"
       providerName="System.Data.SqlClient" />
    </connectionStrings>
</configuration>