As with any exam, it will vary from person to person as to what is deemed to be difficult. Some of the topics you may have trouble with are Windows Presentation Foundation (WPF), Windows Forms and Databound Controls. Each of these topics is outlined below.
Windows Presentation Foundation
Windows Presentation Foundation is essentially an Application Programming Interface for creating a graphical user interfaces for the Windows platform. Some features built into WPF are Direct3D, Data Binding, Media Services, Animations, Documents and Text. Windows Presentation Foundation provides developers with a unified programming model for building Windows smart client user experiences that incorporate User Interface, media, and documents.
A Windows Forms application is an application that uses top level windows, also known as forms, and common user interface controls, such as buttons, text and boxes to interact with the end user. It is seen as a replacement for the earlier and more complex C++ based Microsoft Foundation Class Library. A Windows Forms application is an event-driven application, which means that the form is presented and waits for a user to do something, such as fill in a text box or click a button.
A databound Web control is one that can be declaratively bound to a data source Web control. It is meant to be used on a page when you want to display a single column from a single database record without having to write code or use a DetailsView or FormView control. An important thing to remember when working with properties for a databound control is that for those properties whose value affects the data binding output, you need to instruct the control to rebind to its data source when those values change.