Morning,

How can I solve this problem?
When I try to add SQL Database to my project in C# 2005, it alerts me the message "Connections to SQL Server files (*.mdf) require SQL Server Express 2005 to function properly. Please verify the installation of the computer or download from the URL:http://go.microsoft.com/fwlink/LinkID=49251". Obviously, I installed Microsoft SQL Server 2005 in my computer already.

Regards,
Visoth

Just another step straight into coding.

It's funny how this happens. Just a few days ago I got this same error and spent quite a while trying to figure out what the problem was. It turned out that my installed instance of SQLServer Express was under a name that didn't match what Visual Studio was expecting.

Visual Studio expects a SQL instance called "SqlExpress" by default. This is also the default instance name of Sql express.

In Visual Studio go to Tools -> Options... -> Database Tools -> Data Connections -> SQL Server Instance Name. There you can see what it is set to and change it if necessary.

To check your running instances, in Windows go to Start -> Programs -> Microsoft SQL Server 2005 -> Configuration Tools -> SQL Server Configuration Manager. Then look under the SQL Server 2005 Services node to see all the server services that you have set up. In each service's name will be an instance name. Unfortunately, if one of these is actually the machine's "default instance" it is not obvious, they all have names.

Verify that you have at least 1 instance running and that it's name matches that in Visual Studio.

After re-reading your post to make sure I answered everything, I noticed you say "I installed Microsoft SQL Server 2005". Did you install the regular/full version of the express version? The full version does not allow dynamic connections to mdf files.

-Peter

Hey bro..! the problem still happens. So, how to do? Do something wrong with computer or what?

Just another step straight into coding.