Exception in C# Code with AX2012

Hi I wrote a code part in C# and get the following error:

Could not load file or assembly 'Microsoft.Dynamics.Ax.Xpp.Support, Version=6.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified

What am I missing or what did I do wrong?