您可以测试以下方法。

a Check the connection string of the project. b Go to services and restart SQLServer Instance. c Open 'SQLServer Configuration Manager' In the left panel select 'SQLServer Network Configuration' and expanding it Select 'Protocols for MSSQLServer' In the right panel dbl click on 'TCP/IP' In the 'Protocol' tab set the 'Enabled' to 'Yes' In the 'IP Addresses' tab scroll to down In the 'IPAll' set 'TCP Port' to 1433 d Open 'Firewall with advanced security' In the right tab select 'Inbound Rules'

在中间选项卡找到“本地端口”是1433的记录，如果你找不到它，尝试用以下级别创建它

In the Start menu, click Run, type 'WF.msc', and then click OK In the left panel click the 'Windows Firewall with Advanced Security' In the right panel right-click 'Inbound Rules', and then click 'New Rule' In the Rule Type dialog box, select 'Port', and then click Next In the Protocol and Ports dialog box, select 'TCP', and select 'Specific Local Ports', and then type the port number 1433, Click Next In the Action dialog box, select Allow the connection, and then click Next In the 'Profile' dialog box, checking the Domain, Private and Public, Then click Next In the 'Name' dialog box, type 'SQL 1433 Port' and for a description write description for own. Then click Finish

Then in the middle tab double click the found item(Instance) or created item of 'SQL 1433 Port' name by you. Select 'Scope' tab in opened dialog box(SQL Server Properties) In the Local PC Go to google.com in your Browser and search 'My IP'. then copy of your 'IP' Go to the remote server and in the 'SQL Server Properties' dialog box of 'Scope' tab, in the 'Remote IP Address' select the 'These IP Addresses' option and click 'Add' button In the opened dialog box(IP Address) select 'This IP Address or Subnet' option and paste your 'IP', click OK button.

把我的高度好评的评论作为一个截图的回答。

我在这上面花了很多时间，最后对我有用的是:

1)打开Sql Server Configuration Manager—> Sql Server Network Configuration—> Protocols for <(INSTANCE)>—> TCP/IP(双击它)。

2)选择“——> IP Addresses(Tab)”。

3)转到最后一个条目IP All，并提到TCP端口1433。

4)按“Win+R”，输入services.msc。

5)现在重启SQL Server <(INSTANCE)>。

在这之后，问题解决了!

我将使用Entity Framework的项目设置为启动项目，然后运行update-database命令，解决了这个问题。

我发现以下技巧很有用:

Make sure your database engine is configured to accept remote connections: Start > All Programs > SQL Server 2005 > Configuration Tools > SQL Server Surface Area Configuration Click on Surface Area Configuration for Services and Connections Select the instance that is having a problem > Database Engine > Remote Connections Enable local and remote connections Restart instance You may need to create an exception on the firewall for the SQL Server instance and port you are using: Start > Run > Firewall.cpl Click on exceptions tab Add sqlservr.exe (typically located in C:\Program Files (x86)\Microsoft SQL Server\MSSQL.x\MSSQL\Bin, check your installs for the actual folder path) and port (default is 1433) Check your connection string as well From FIX : ERROR : Could not open a connection to SQL Server: Check if your SQL server services is up and running properly: Go to All Programs > Microsoft SQL Server 2008 > Configuration Tools > SQL Server Configuration Manager > SQL Server Services Check to make sure SQL Server service status is Running. In addition, ensure that your remote server is in the same network. Run sqlcmd -L to ascertain if your server is included in your network list. Enable TCP/IP in SQL Server Configuration When two or more SQL Servers are connected across network they do all communication using TCP/IP. The default port of SQL Server installation is 1433. This port can be changed through SQL Server Configuration Manager. TCP/IP should be enabled for SQL Server to be connected. Go to All Programs >> Microsoft SQL Server 2008 >> Configuration Tools >> SQL Server Configuration Manager >> Select TCP/IP Right Click on TCP/IP >> Click on Enable You must restart SQL Server Services for all the changes to take effect. Right click and go to menu properties to select location where default port of SQL Server can be changed.

我知道这是隐藏的，但是当我移动一个数据库时，没有给NT服务\MSQLSERVER帐户权限到我移动数据库文件的目录时，我造成了这个问题。授予权限并重新启动SQLServer完成了任务。

当我在Visual Studio中遇到这个错误时，

"在建立与SQL Server的连接时，发生了与网络相关或特定于实例的错误。未找到服务器或无法访问服务器。验证实例名称是否正确，SQL Server是否配置为允许远程连接。(提供商:命名管道提供商，错误:40 -无法打开到SQL Server的连接)"

.．.它是在执行下面的c#代码期间，它试图获取我的SQL Server数据以在网格中显示。中断恰好发生在表示connect.Open()的行上:

        using (var connect = Connections.mySqlConnection)
        {
            const string query = "SELECT Name, Birthdate, Narrative FROM Friends";
            using (var command = new SqlCommand(query, connect))
            {
                connect.Open();
                using (var dr = command.ExecuteReader())
                {
                    while (dr.Read())
                    {
                        // blah
                    }
                }
            }
        }

It was inexplicable because the SQL query was very simple, I had the right connection string, and the database server was available. I decided to run the actual SQL query manually myself in SQL Management Studio and it ran just fine and yielded several records. But one thing stood out in the query results: there was some improperly encoded HTML text inside a varchar(max) type field within the Friends table (specifically, some encoded comment symbols of the sort <!-- lodged within the "Narrative" column's data). The suspect data row looked like this:

Name    Birthdate    Narrative
====    =========    ============== 
Fred    21-Oct-79    <!--HTML Comment -->Once upon a time...

注意编码的HTML符号“&lt;”，它代表一个“<”字符。不知何故，它进入了数据库，而我的c#代码无法接收它!它每次都失败在connect.Open()行!在我手动编辑数据库表Friends中的一行数据并输入解码后的“<”字符之后，一切都正常了!这一行应该是这样的:

Name    Birthdate    Narrative
====    =========    ============== 
Fred    21-Oct-79    <!--HTML Comment -->Once upon a time...

我使用下面这个简单的UPDATE语句编辑了一个不好的行。但如果你有几行违规的HTML编码，你可能需要一个更详细的UPDATE语句，使用REPLACE函数:

UPDATE Friends SET Narrative = '<!--HTML Comment -->Once upon a time...' WHERE Narrative LIKE '&lt%'

因此，这个故事的寓意是(至少在我的情况下)，在将HTML内容存储到数据库之前清理它，这样您就不会在第一时间得到这个神秘的SQL Server错误!(如果你需要更多信息，正确地消毒/解码你的HTML内容是另一个值得单独在StackOverflow搜索的讨论主题!)