你调用的对象是空的.连接概率. [英] Object reference not set to an instance of an object. connection prob.

问题描述

我尝试了1和2，但没有工作

1.private string constring = ConfigurationSettings.AppSettings ["constring"].ToString();
2.private string constring = ConfigurationManager.ConnectionStrings ["constring"].ConnectionString;

连接问题.
错误消息=对象引用未设置为对象的实例

Gaurang R.

i have tried 1 and 2 but not working

1.private string constring = ConfigurationSettings.AppSettings["constring"].ToString();
2.private string constring=ConfigurationManager.ConnectionStrings["constring"].ConnectionString;

connection strting problem.
ERROR message=Object reference not set to an instance of an object

Gaurang R.

推荐答案

您需要学习使用调试器.此错误表示它的意思. constring不是您的连接字符串或配置设置中的值.如果是这样，则不需要在其上调用ToString，它应该是一个字符串.

You need to learn to use a debugger. This error means what it says. constring is not a value in your connection strings or configuration settings. If it was, it would not need ToString called on it, it should be a string.

如果您的解决方案中有多个项目，并说启动项目是web应用程序，并且您拥有下面的代码

If you having multiple project in your solution, and say the startup project is webapplication and you having the below code

<connectionstring>
<add name="" mode="hold" /></connectionstring>

数据访问层(DAL)[类库项目]配置文件中的文件意味着没有任何意义，您不必在启动项目中将其添加为web应用程序的web.config文件.

in Data Access Layer (DAL)[class library project] configuration file means that doesn''t make any sense you have to add that in startup project say here as webapplication''s web.config file.

我解决了.


必须添加参考-> .net-> System.Configuration

如果已使用system.configuration添加，请再次添加参考

然后
私有字符串constring = ConfigurationManager.ConnectionStrings ["constring"].ConnectionString;

它会正常工作

高朗河.

i have solved.


have to Add reference-> .net-> System.Configuration

add reference again if you have added using system.configuration

then
private string constring = ConfigurationManager.ConnectionStrings["constring"].ConnectionString;

it will work properly

Gaurang R.

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