When trying to query data from Entity Framework, my code always return the following error:
The underlying provider failed on Open.
Here’s the screenshot.

Turn out the problem was on the Connection String for the entity.
In the config file, we have to include “Password” parameter in “connectionString” attribute.
<connectionStrings>
<add name="SomeEntities" connectionString="metadata=res://*/Models.DB.csdl|res://*/Models.DB.ssdl|res://*/Models.DB.msl;provider=System.Data.SqlClient;provider connection string="Data Source=SERVER\INSTANCE;Initial Catalog=Database;User ID=username;Password=password;MultipleActiveResultSets=True"" providerName="System.Data.EntityClient" />
</connectionStrings>
Whoolaa, it works now!
UPDATE (03.07.2011): If you still see this error message when running on IIS, please read this post.
Lloyd Hasson
August 13, 2012 at 9:43 pm
Wow, it worked! Thanks very much. Brilliant!
sojansojanchandy
March 3, 2013 at 10:40 pm
it didnt work for me.i already password had any suggesssion