Question

I have a really simple question here, but I just can’t find an answer that solves it.

I have a connection string like this:

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\DB\DB.mdf;Initial Catalog=DB;Integrated Security=True");

It works, but when I try to use it in a PC that doesn’t have SQL Server Express installed, it just won’t connect. It’ll obviously work if I remove that “\SQLEXPRESS” piece, I know, but I’d prefer not to do it manually on each PC I install the software. I tried to do it by using try-catch, but it’s too slow and I think it isn’t very recommended.

Well, I just want to know how to do it via code. Is there a simple way to do so? Will it solve the problem completely? (I mean, will it certainly work in other editions?)

Thanks in advance! (And sorry for my English)

Answer 1

Just to clarify: A SQL server can be installed as a ‘default’ or a ‘named’ instance. I think by default, express installs as a named instance

This allows a single server machine to run multiple SQL servers

To connect to a default instance you specify the server name or IP and that’s all

Server=SomeServer

To connect to a named instance you specify the server/ip + instance name separated by a backslash.

Server=SomeServer\SomeInstance

In your case you are looking to connect to a SQL instance called ‘SQLEXPRESS’ on the local machine. (a dot . means local machine)

You ideally want to install SQL on a server machine and use an application configuration file (App.config) to specify the connection string..

App.config supports a section called ConnectionStrings which you can add your connection string to. Then if you add a reference to System.Configuration to your project you can get hold of the connectionstring using the config manager class:

App.config:

<connectionStrings>
    <add name="YourConnectionString"
        connectionString="Server=someSqlServer\SomeInstance;Initial Catalog=SomeDB;Integrated Security=True" 
providerName="System.Data.SqlClient" />
</connectionStrings>

Use in code:

ConfigurationManager.ConnectionStrings["YourConnectionStringName"]