在使用C#操作IIS创建应用程序池出现异常：无效索引（Exception from HRESULT:0x80070585）

相关代码：

public static string CreateAppPool(string appPoolName, string frameworkVersion, string managedPipelineMode)
{
   DirectoryEntry rootfolder = new DirectoryEntry("IIS://localhost/W3SVC/APPPOOLS");
   try
   {
       DirectoryEntry appPool = rootfolder.Children.Add(appPoolName, "IIsApplicationPool");
       if (appPool.Properties.Contains("AppPoolCommand"))
       {
           appPool.Properties["AppPoolCommand"][0] = "1";
       }
       if (appPool.Properties.Contains("ManagedRuntimeVersion"))
       {
           appPool.Properties["ManagedRuntimeVersion"][0] = "v4.0";
       }
       //以下代码在WindowsServer2008版本为6.0的系统上会出现异常：
       //无效索引（Exception from HRESULT:0x80070585）
       //if (appPool.Properties.Contains("AppPoolIdentityType"))
       //{
       //    appPool.Properties["AppPoolIdentityType"][0] = "4";
       //}
       if (appPool.Properties.Contains("Enable32BitAppOnWin64"))
       {
           appPool.Properties["Enable32BitAppOnWin64"][0] = true;
       }
       appPool.CommitChanges();
       return null;
   }
   catch (System.Exception ex)
   {
       LogToFile.Save(ex, "CreateAppPool");
       return ex.Message;
   }
}

将相关代码注释以后，未见对Web应用程序带来任何影响。