Could not load file or assembly 'Oracle.DataAccess' or one of its dependencies. An attempt was made to load a program with an incorrect format.

I have installed a Web application on IIS 7.0 windows server 2008 R2 64 bit OS 
I am refering a oracle.DataAccess.dll
When i try to acess the application i am getting the below message
"Could not load file or assembly 'Oracle.DataAccess' or one of its dependencies. An attempt was made to load a program with an incorrect format.".

解决办法：     need to enable 32-bit applications in your AppPool.