遇到文化和 NullReferenceException 问题

Question

我正在尝试编写登陆页面代码，通过阅读文化将决定请求是否被重定向到英语网站或斯洛伐克语网站。

代码如下：

public partial class _default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string strCountry = ResolveCountry().ToString();
        if (strCountry == "SK")
        {
            Response.Redirect("/sk/");
        }
        else
        {
            Response.Redirect("/en/");
        }
    }

    public static CultureInfo ResolveCulture()
    {
        string[] languages = HttpContext.Current.Request.UserLanguages;

        if (languages == null || languages.Length == 0)
            return null;

        try
        {
            string language = languages[0].ToLowerInvariant().Trim();
            return CultureInfo.CreateSpecificCulture(language);
        }
        catch (ArgumentException)
        {
            return null;
        }
    }

    public static RegionInfo ResolveCountry()
    {
        CultureInfo culture = ResolveCulture();
        if (culture != null)
            return new RegionInfo(culture.LCID);

        return null;
    }
}

问题是在浏览器中它看起来没问题，它会将您重定向到该站点： http:// www.alexmolcan.sk

但是在检查 IIS 日志时，Google 网站管理员工具或 http://www.rexswain.com/httpview.html 我总是收到 500 ASP 错误：

 Object·reference·not·set·to·an·instance·of·an·object.
 System.NullReferenceException:·Object·reference·not·set·to·an·instance·of·an·object.

响应标头：

HTTP/1.1·500·Internal·Server·Error
Connection:·close
Content-Length:·4684

当我在本地调试项目时，它总是可以毫无问题地编译。我不知道我做错了什么

谢谢。

编辑

异常

Process information: 
   Process ID: 4068 
   Process name: w3wp.exe 
   Account name: IIS APPPOOL\ASP.NET v4.0 

Exception information: 
   Exception type: NullReferenceException 
   Exception message: Object reference not set to an instance of an object.
   at sk_alexmolcan._default.Page_Load(Object sender, EventArgs e) in default.aspx.cs:line 15
   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean  includeStagesAfterAsyncPoint)

Answer 1

我认为你正在抛出，因为当 ResolveCountry 返回 null 时，你的 .ToString() 和 if(strcountry == "SK") 将抛出。

无法将 null 转换为字符串。尝试

CultureInfo cul = ResolveCountry();
string strCountry = cul== null ? string.empty : cul.ToString();

if (strCountry == "SK") {}