I want to share same Database information across multiple entities in Silverlight.. but I want the connection string to be named xyz and have everyone access that connection
Instead of using config files you can use a configuration database with a scoped systemConfig table and add all your settings there.
CREATE TABLE [dbo].[SystemConfig]
(
[Id] [int] IDENTITY(1, 1)
NOT NULL ,
[AppName] [varchar](128) NULL ,
[ScopeName] [varchar](128) NOT NULL ,
[Key] [varchar](256) NOT NULL ,
[Value] [varchar](MAX) NOT NULL ,
CONSTRAINT [PK_SystemConfig_ID] PRIMARY KEY NONCLUSTERED ( [Id] ASC )
WITH ( PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON ) ON [PRIMARY]
)
ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[SystemConfig] ADD CONSTRAINT [DF_SystemConfig_ScopeName] DEFAULT ('SystemConfig') FOR [ScopeName]
GO
With such configuration table you can create rows like such:

Then from your your application dal(s) wrapping EF you can easily retrieve the scoped configuration.
If you are not using dal(s) and working in the wire directly with EF, you can make an Entity from the SystemConfig table and use the value depending on the application you are on.