Environment variables in ASP.NET web.config file

Question

I was wondering why can't I use a custom environment variable in an ASP.NET web.config file like so?

<?xml version="1.0"?>
<configuration>
  <connectionStrings>
    <add name="ConnectionName" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename='%MyProjectsFolder%\WebAppName\App_Data\Database1.mdf';User Instance=true" providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

I checked through Start -> Run that the file path to .mdf file is valid.

When I run my C# code to connect to database I get the following error:

An attempt to attach an auto-named database for file %MyProjectsFolder%\WebAppName\App_Data\Database1.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.

what is the alternate solution you used ?

coding_idiot
– coding_idiot

2017-01-21 01:47:33 +00:00
Commented Jan 21, 2017 at 1:47 — coding_idiot
– coding_idiot, Commented Jan 21, 2017 at 1:47

John Saunders · Accepted Answer · 2012-02-22 01:45:38Z

6

Environment variables may not be used in a config file.

answered Feb 22, 2012 at 1:45

John Saunders

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1 Comment

ahmd0 Over a year ago

Any other way to use relative paths?

Steve Wellens · Accepted Answer · 2012-02-22 02:33:07Z

1

You can use: DataDirectory like this:

“Data Source = |DataDirectory|\Mydb.sdf”

And you can change where DataDirectory points: "To set the DataDirectory property, call the AppDomain.SetData"

http://social.msdn.microsoft.com/Forums/en/sqlce/thread/dc31ea59-5718-49b6-9f1f-7039da425296

Caveat, I've never tried this.

answered Feb 22, 2012 at 2:33

Steve Wellens

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Steve Wellens Over a year ago

The thing is, if you need to read the correct directory from some config file to set it, you might was well just modify the connection string in the web.config file.

pete · Accepted Answer · 2012-02-22 01:35:21Z

0

I don't suppose you've tried:

connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename='~/App_Data/Database1.mdf';User Instance=true"

answered Feb 22, 2012 at 1:35

pete

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4 Comments

ahmd0 Over a year ago

You see the database file is located in a project other than mine.

pete Over a year ago

Have you tried browsing to it and selecting it in the "Data Connections" browser?

ahmd0 Over a year ago

I don't want to hardlink to it. The reason for that is because this project might be moved to and from another computer with a different file path.

John Saunders Over a year ago

It's not "hard linked". It's in a text file. It can be edited.

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