SQL Server express和SQL Server的连接字符串有什么区别吗？

Question

In my application, i make a dynamic connection string:

server = "Server  = .\\" + this.comboBoxListInstances.SelectedItem.ToString() + ";";
connectionString = server + attachDatabase + databaseName + "Integrated Security = true";

On my laptop (using SQL server 2008 express), the result is:

// server = "Server = .\\SQLEXPRESS;" (I select SQLEXRESS in comboBox)
// attachDatabase = "AttachDbFileName = |DataDirectory|\\Resources\\DT.mdf;"
// databaseName = "Database = DATA;";
// so the conectionString is : "Server = .\\SQLEXPRESS;AttachDbFileName = |DataDirectory|\\Resources\\DT.mdf;Database = DATA;Integrated Security = true"

I read registry to find all SQL server Instances and let the user choose which they want.
This conectionString work fine on my laptop and my friend who use SQL server express too. However, when i run my app on another friend's laptop with SQL server 2008 R2 installed, it throws an exception:

It say the connection string is invalid, It is :

"Server = .\\MSSQLSERVER;AttachDbFileName = |DataDirectory|\\Resources\\DT.mdf;Database = DATA;Integrated Security = true"

when I try to temporarily disable comboBoxListInstance and use this conectionString

"Server = (local);AttachDbFileName = |DataDirectory|\\Resources\\DT.mdf;Database = DATA;Integrated Security = true"

The app works! So, I think there is a difference between the conection string for SQL server express and SQL server. Is it right? There is a question similar to mine here , and they say that there is no difference. If they are right, what is the problem of my connectionString?

P/S: sorry for my bad grammar

Answer 1

It looks like you just proved that SqlExpress installs its default named instance as "MSSQLSERVER" where as full sql installs an unnamed default instance of blank.

(local) means " .\\ " " 127.0.0.1" WHATEVER instance is at 1433.

.MSSQLEXPRESS means explicitly .\\MSSQLEXPRESS which may or may not be the (local) default instance.

As An Aside usually the most relevant difference at this point is that regular SQL will install with the ports open and TCP clients ready to go.

SQL Express will only allow local "dev" type of connections until you activate the external ports and client protocols.