# .NET Error 26: Can't find SQL Server



## slbergh (Mar 30, 2011)

I've been fighting with this all day. I have a .NET web application that connects to SQL Server 2008. On my machine and 3 others, it runs beautifully. A couple of minutes, a few mouse clicks, and it's up and running.

Now my client's server is another story. No matter what I try, I keep getting the Cannot find SQL Server or Instance error (affectionately known as error 26). I've tried creating a new instance of the database. I've added the website again and again and again...at least 60 times today alone. I've created a database user for NT AUTHORITY\NETWORK SERVICE and set appropriate permissions. SQL Server is configured to allow remote connections (SQL and IIS are running on the same machine). TCP/'IP is enabled. 

I have remote access into their machine, but the machine has been pretty locked down (the video player on the login page won't even load).

Does anyone have any ideas for getting this to work that I haven't already tried?


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## ehymel (Aug 12, 2007)

Sounds like a firewall problem. I don't know this platform, but make sure the appropriate port is opened to communication with SQL Server.


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## slbergh (Mar 30, 2011)

Checked that. It was fine.


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## ehymel (Aug 12, 2007)

Is the SQL Server Browser service running?


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## slbergh (Mar 30, 2011)

Yes it is. 

We finally got the connection working when we ended up installing SQLExpress over the top. (We'd made sure to change the connection strings when we were working with the standard version.) Our guess is that something didn't register properly when the .NET 4.0 framework was installed after SQL Server was initially installed.


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