The entry '' has already been added error

I have a web.config in ASP.net giving me configuration error.

 <connectionStrings>   
<add name="conn1" connectionString="Data Source=test;database=test;uid=test;pwd=test"/>
<add name="conn2" connectionString="Data Source=123.123.1.123;database=test2;uid=test;pwd=test"/>
...

It throws "The entry 'conn2' has already been added." error. I know I only added it once. Not sure what it is wrong with.

it can be in web.config that is parent to this one. just add

<remove name="conn2" />

before your add it (again) :)

alternatively clear all connection string using

<clear />

You should use <clear /> when adding any providers to your web.config. Read this article: http://weblogs.asp.net/scottgu/archive/2006/11/20/common-gotcha-don-t-forget-to-clear-when-adding-providers.aspx

The root cause of the above problem rests in how the new provider was registered within the web.config file.

The section within the web.config file is implemented as a collection, and so it is possible to register multiple providers at the same time

If you have another project using the same connection string name you will receive this error because that connection string has already been added to the collection.