ODP。无法找到所请求的。NET框架数据提供程序

I am trying to develop an ASP.NET MVC 4.0 application using Oracle 11g Express and the .NET 4.0 framework. I can connect to the DB using the ODP.NET provider and can also generate my EDMX against the database. What I can't do is query the underlying DB using entity framework. When instantiating my DbContext using the connectionString Visual Studio generated, I get the following error:I am trying to develop an ASP.NET MVC 4.0 appli