SQL网络接口，错误：26-错误定位服务器/实例指定不使用SQL Server Express

Question

There are numerous posts regarding the SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified and I tried the suggested solutions with no success. I'm migrating an ASP.NET 4 VB web application developed in VS 2010 Windows Server 2008 R2 to a new server Windows 2012 R2 with VS 2012 and a full developer version of SQL Server 2012 installed. The server has IIS installed and the application has been added here as well. The security permissions have been set up for users IUSR, IIS_IUSRS and even the application pool.

My SQL Server 2012 has a named instance which I can connect to using server authentication with no issues and adding the connection string in VS Server Explorer was successful.

There 3 other ASP.NET applications working applications on that box which have successfully connected to SQL Server. I have modified my web.config file to emulate the working applications countless times with no success.

Based on what I have read, the machine.config file is looking for the LocalSqlServer connection string but adding/removing this in the web config makes no difference. The connection string I set up is named "myConn" and I verified the SQL Server name instance is correct, the service is enabled, the SQL Browser is also enabled and the firewall is not even on at this point. The connectiong string was added by Visual Studio but like I mentioned before; it makes no difference if I remove it.

Any help will be greatly appreciated.

Here is my web.config:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <connectionStrings>
    <remove name="LocalSqlServer"/>
    <add name="myConn" connectionString="Data Source=MY-SQLServer;Initial Catalog=Sales;Persist Security Info=True;User ID=sa;Password=******; Pooling=true;Connection Lifetime=0; Min Pool Size=2; Max Pool Size=600; Connection Timeout=60" providerName="System.Data.SqlClient" />
    <add connectionString="data source=.\SQLExpress;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=false" name="LocalSqlServer" providerName="System.Data.SqlClient" />

  </connectionStrings>
  <system.web>
    <authentication mode="Forms">
    </authentication>
    <compilation debug="true" strict="false" explicit="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
        <add assembly="stdole, Version=7.0.3300.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
        <add assembly="Office, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71E9BCE111E9429C" />
        <add assembly="Microsoft.Office.Interop.Word, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71E9BCE111E9429C" />
        <add assembly="Microsoft.Office.Interop.Excel, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71E9BCE111E9429C" />
        <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
        <add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
      </assemblies>
    </compilation>
        <identity impersonate="true" password="*****" userName="Domain\adminUser" />

  </system.web>
  <system.webServer>
    <security>
      <requestFiltering>
        <fileExtensions>
          <add fileExtension=".docx" allowed="true" />
          <add fileExtension=".dotx" allowed="true" />
        </fileExtensions>
      </requestFiltering>
    </security>
  </system.webServer>
</configuration>

Here is a snippet of the Login.aspx.vb code:

 Dim cn As New SqlConnection 'SQL Connection
                 cn.ConnectionString = ConfigurationManager.ConnectionStrings("myConn").ConnectionString
                 cn.Open() 'open sql connection
                 Dim cmd As New SqlCommand
                 cmd.CommandType = CommandType.Text
                 cmd.Connection = cn
                 cmd.CommandText = "select count(*) from Sales where email='" & LoginUser.UserName.ToString"
                 Try
                     Dim x As Integer = cmd.ExecuteScalar()
                     If x > 0 Then
                         cn.Close()
                         Session("user") = LoginUser.UserName.ToString()
                         Response.Redirect("~/Default.aspx", False)
                     Else
                         cn.Close()
                         LoginUser.FailureText = "Login error message."
                    End If
                 Catch ex As Exception
                     cn.Close()
                    LoginUser.FailureText = ex.Message & "<br/ >Please try logging in again."
            End Try

Answer 1

You say that you have a named instance of SQL Server Developer Edition but neither of the connection strings you have in that config file indicate that. If the Data Source in the connection string is set to "SQLS2012" then that means a default instance on a machine with that name. A named instance on the local machine should be ".\\InstanceName", "(local)\\InstanceName" or "MachineName\\InstanceName".