RouteData.Values查询字符串时，返回的NullReferenceException不存在 [英] RouteData.Values Return NullReferenceException when querystring is not present

问题描述

如何处理NullReferenceException为下面的语句，因为我得到null异常错误下面的语句，如果它在查询字符串中不存在使用URL路由

How do I handle NullReferenceException for the below statement as I get null exception error for the below statement if it is not present in the query string when using URL Routing

string lang = RouteData.Values["Language"].ToString();

错误详情

在当前Web请求的执行期间发生异常。

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

异常详细信息：System.NullReferenceException：未将对象引用设置为实例的对象。

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

推荐答案

你得到这个异常，因为RouteDate.Values [Language]为null， ToString就可以了。

只是添加一个if来检查null

You are getting this exception because RouteDate.Values["Language"] is null and you are applying instance method .ToString on it.
just add an if to check for null

string lang="";
if(RouteData.Values["Language"] != null)
      lang = RouteData.Values["Language"].ToString();

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