命名空间 System.Configuration 中不存在 configurationManager

Question

I have used the following namespace to connect my project to the sql server:

using System.Configuration;

and also used

string str=System.Configuration.ConfigurationSettings.AppSettings["myconnection"];
SqlConnection oconnection = new SqlConnection(str);
oconnection.Open();

when I run the program ,an error has been occurred and show the message

'System.Configuration.ConfigurationSettings.AppSettings' is obsolete.This method is obsolete,it has been replaced by 'System.Configuration! System.Configuration.ConfigurationManager.AppSettings '

but I have no found ConfigurationManager in that namespace and for oconnection.Open(); the message is

InvalidOperationException

was unhandled.

What can I do?

Answer 1

Go to references, and add a reference to System.Configuration

Once you have done this, you should be able to reference System.Configuration.ConfigurationManager .

string str = System.Configuration.ConfigurationManager.AppSettings["myconnection"];
SqlConnection oconnection = new SqlConnection(str);
oconnection.Open();

From MSDN: The ConfigurationManager class enables you to access machine, application, and user configuration information. This class replaces the ConfigurationSettings class, which is deprecated.

http://msdn.microsoft.com/en-us/library/system.configuration.configurationmanager.aspx

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Edit: Addiitonal Information

In reference to the InvalidOperationException . This is caused when the connection string does not specify a data source or server. I am guessing that your connection string is empty.

In your web.config check the location of your connection string. If it falls under the element, then you will need to change your code to search ConnectionStrings and not AppSettings .

string str = System.Configuration.ConfigurationManager.
    ConnectionStrings["myconnection"].ConnectionString;

Answer 2

如果解决方案中有多个项目，则必须将参考System.Configuration添加到每个项目中， ConfigurationManager才能在其中任何一个项目中工作。

Answer 3

在您的项目中添加一个引用：System.Configuration.dll，然后ConfigurationManager 将可用

Answer 4

在最新版本的 Visual Studio 中，我不得不通过 NuGet 包管理器添加 System.Configuration.ConfigurationManager。

Answer 5

Install System.Configuration from nuget package. Then add reference.