To write and run C# code that use the Trust Services SDK, you must add references to the SDK DLLs (installed by the MSI) to the C# project.
In the case of the provided code samples, when you open the "References" folder under the project in Visual Studio 2010, you will see invalid references to the Trust SDK DLLs as shown below.

These DLL references need to be deleted and re-added, by right clicking on the "References" folder, and selecting "Add Reference...".
If this is an empty new C# project that you are writing, you'll need to add these DLLs in the same manner.
After selecting "Add Reference...", browse to the location where the SDK DLLs were installed. By default these are:
On a 64-bit machine:
if you installed the 64-bit MSI:
c:\Program Files\Microsoft\Trust Services Lab SDK and Shell (x64)\bin
if you installed the 32-bit MSI:
c:\Program Files (x86)\Microsoft\Trust Services Lab SDK and Shell (x86)\bin

On a 32-bit machine you have to install the 32-bit MSI, and the DLLs are located under:
c:\Program Files\Microsoft\Trust Services Lab SDK and Shell (x86)\bin

Currently, the Trust Services SDK is provided as 5 DLLs. Unless, you are familiar with which DLL has the functionality you require, we recommend you add references to all 5 DLLs (listed below) to your project: