SQL connection failure in LINQ-to-SQL

Question

I'm cloning a local C#-SQL Windows Forms application to a new laptop. I've successfully cloned the C# project and back-up-and-restored the SQL database to the new machine, but the new project is unable to read/query any data from the new, cloned SQL database.

Since the SQL DB is local, the LINQ-to-SQL addressing is slightly different on account of the computer having a different name. So, I deleted the SQL table representations from the existing LINQ .dbml's graphical interface, removed the old server connection from the Server Explorer, added the new server connection, and click-and-dragged the table objects from the Server Explorer's new Data Connection object to the now-empty .dbml file.

Upon rebuilding and running the application in debug mode, I found that the dropdown menus which pull from the SQL DB are empty. Upon trying a button function which pulls from the database, I get the following error:

SqlException was unhandled A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

(The cloned SQL server is configured to allow remote connections, TCP/IP is enabled in SQL, and the original C#-SQL application works without a hitch.)

Rondel · Accepted Answer · 2011-12-06 21:07:07Z

2

Check in your Web.Config and make sure that your Connection String is set up correctly. Also check to make sure that when you initialize your DataContext that you are using the correct Connection string from your Web.Config.

Sometimes when you remove dbs from the dbml, it doesn't completely clear the web.config of the old entries. Look for a line like this in your designer.cs file:

public SomeDbDataContext() : 
            base(global::System.Configuration.ConfigurationManager.ConnectionStrings["SomeDbConnectionString"].ConnectionString, mappingSource)
    {
        OnCreated();
    }

Compare it with the connectionStrings in your web.config

<connectionStrings>
<add name="ApplicationServices" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient" />
<add name="someDBConnectionString" connectionString="Data Source=SomeServer;Initial Catalog=SomeDB;Integrated Security=True" providerName="System.Data.SqlClient" /> 
<add name="theOLDDBConnectionString" connectionString="Data Source=SomeServer;Initial Catalog=OldDB;Integrated Security=True" providerName="System.Data.SqlClient" />
</connectionStrings>

edited Dec 6, 2011 at 21:07

answered Dec 6, 2011 at 20:05

Rondel

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6 Comments

Jack Huang Over a year ago

When I find that kind of line, should I delete it?

Rondel Over a year ago

No don't delete it. Make sure that the OnCreated() is using the correct connection string from the Web.Config. I updated my answer to show what it may look like. If it is using the old connection string, just update the line.

Jack Huang Over a year ago

I can't find a Web.config for my C# project (I found two for my SQL server, but they don't have ConnectionString specifiers). However, I found a designer.cs line that says this: public DataClasses1DataContext() : base(global::TradingSystem2.Properties.Settings.Default.PJMConnectionString1, mappingSource) { OnCreated(); }

Jack Huang Over a year ago

In the definition of the PJMConnectionString1 object, The database parameter is correct: I looked at the definition of the PJMConnectionString1 object, and it contains the correct database address : [global:: ...DebuggerNonUserCodeAttribute()] [global:: ...ConnectionString)] [global::System.Configuration.DefaultSettingValueAttribute("Data Source=ZUOXIANG-HP\\ENERGY;Initial Catalog=PJM;Integrated Security=True")] public string PJMConnectionString1 { get { return ((string)(this["PJMConnectionString1"])); } }

Jack Huang Over a year ago

Also, There's no Web.config for the original, fully functional C# project that I cloned this current one from, so it doesn't seem like the lack of a Web.config itself is the problem.

|

competent_tech · Accepted Answer · 2011-12-06 20:03:44Z

1

I would check a few things:

1) Is SQL Server started on the new machine?

2) Is the firewall configured to allow SQL connections?

3) Is the client connection mechanism (named pipes, tcp/ip) also configured in SQL Server.

4) Is there a valid network connection in the new machine (we used to have a lot of problems on laptops when they were not connected to the network).

You might have much better luck if you change the SQL Server machine name to . or (local) if you are always going to have the DB installed on the same machine as the app.

answered Dec 6, 2011 at 20:03

competent_tech

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2 Comments

Jack Huang Over a year ago

1. Yes; 2. Yes; 3. TCP/IP is enabled, Named Pipes is not, but when I enabled Named Pipes, my SQL Server instance would not start; 4. The database is entirely local on the laptop's hard drive; When you say "change the SQL Server machine name", do you mean the network name of the laptop, or something that's specified in SQL Server config?

competent_tech Over a year ago

@JackHuang: Sorry, I meant the name of the server specified in the connection string within your app.

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