assembly.CreateInstance returns null
<p>I'm working with assembly.CreateInstance, and it returns null, while it was fine using it with a different project with the same DLL file "assembly file", Can you please suggest reasons when and why it returns null?Please this is urgent??</p>

<p><strong>Edit</strong></p>

<p>The type I'm searching for has a default constructor, but it implements another interface, like this. Project1, has the interface A and makes the DLL which contains the new type let it be typeB which implements A. Project2, has the same interface A and use the "CreateInstance" method to locate the type typeB, but here the CreateInstance returns null, any suggestions?</p>
