Windows服务ServicesDependedOn的奇怪问题？？？

代码如下

public partial class WinServicePWServiceInstaller : Installer

{

private ServiceProcessInstaller process;

private ServiceInstaller service;

private const string m_SERVICENAME = "myService";

public WinServicePWServiceInstaller()

{

InitializeComponent();

process = new ServiceProcessInstaller();

process.Account = ServiceAccount.LocalSystem;

service = new ServiceInstaller();

service.ServiceName =m_SERVICENAME;

service.StartType = ServiceStartMode.Automatic;

service.ServicesDependedOn = GetDepengOnServices();

Installers.Add(process);

Installers.Add(service);

}

/// <summary>

///获取配置文件的依赖服务

/// </summary>

/// <returns></returns>

private string[] GetDepengOnServices()

{

string[] services=null;

string allService = ConfigurationManager.AppSettings["DependOnService"];

services = new string[] { allService };

//return services;

if (allService.IndexOf(';') != -1)

{

services = allService.Split(';');

}

else

{

services =new string[]{ allService};

}

return services;

}

}

按以上方法写的 GetDepengOnServices()，在安装过程中报错。

改成一下方法不会报错

/// <summary>

///获取配置文件的依赖服务

/// </summary>

/// <returns></returns>

private string[] GetDepengOnServices()

{

string[] services=null;

string allService = ConfigurationManager.AppSettings["DependOnService"];

services = new string[] { allService };

return services;

//if (allService.IndexOf(';') != -1)

//{

//    services = allService.Split(';');

//}

//else

//{

//    services =new string[]{ allService};

//}

//return services;

}

所读的配置节 <!--本服务依赖的服务列表-->

<add key ="DependOnService" value ="MSSQLSERVER"/>

跟踪后，两种写法都能得出正确的结果，为什么 第一种写法在安装过程中会报错？？？？