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Editorial Team
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Asked: 2026-06-02T19:36:10+00:00

So I have few ASP.NET apps all running off SQL Server Express 2008 and

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So I have few ASP.NET apps all running off SQL Server Express 2008 and working fine and dandy. I just put up a new one to test something and am now getting the Error 26 – can’t find instance. What’s weird is that the app is talking to the DB partially because it brings up the user login page and if I enter wrong data it returns a message about that (which is good). When I enter the correct login info it takes it then thinks for a few seconds and then throws the Error 26.

Here is my connection string —

<connectionStrings>
    <add name="db_BPEntities" connectionString="metadata=res://*/App_Code.Data.db_BP.csdl|res://*/App_Code.Data.db_BP.ssdl|res://*/App_Code.Data.db_BP.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=LOCALHOST\SQLEXPRESS;initial catalog=db_BC_Build;user id=USER;password=PASSWORD;multipleactiveresultsets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
    <add name="Default" connectionString="server=LOCALHOST\SQLEXPRESS;database=db_BC_Build;USER ID=USER;password=PASSWORD;Min Pool Size=10;Max Pool Size=800;Network Library=dbmssocn" providerName="System.Data.SqlClient" />      
</connectionStrings>

Note: I’ve changed user/password info. The DB is running locally off the same box with IIS (it’s a test intranet site so I’m ok with that for now).

So summary:

  1. Other apps running off same DB have zero connectivity issues. They all connect and work fine.
  2. This app partially works but on login throws the Error 26 – Instance not found.
  3. Would it be that there are 2 connection strings here vs 1 connection string on my other DBs?

Really stumped.

Thanks for any/all help 🙂

Edit: I think the issue is with the Entity Framework and SQL Server Express. It seems to connect initially to authenticate the user, but then the EF connectivity to display data, etc is where it breaks. That’s where I’m at right now and stuck in trying to figure this out (I didn’t develop this application).

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1 Answer

  1. Editorial Team

    Try to connect without “Network Library=dbmssocn” in your connectionstring. I have had the same (error 26) issue and it did work for me.

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