How to use an assembly/DLL in Dynamics AX

To use a DLL in Dynamics AX, the DLL must be added to the References node of the AOT.

This can be achieved by right-clicking on the node and select Add Reference. This opens a dialog where - depending on the "location" of the DLL - the following steps must be taken:

• If the DLL is already registered in the Global Assembly Cache (GAC), it should already appear in the list where they can be selected using the checkbox on the left and selected with Select now.
  
  To register a DLL in the GAC, it is necessary that the DLL has been signed.
  They can be achieved via the command line using the following command
  "gacutil / i MyClassLibrary.dll"

• If the DLL for example, is stored in the BIN directory of the client, you must first select it using the Browse button. Now they should appear in the list where they can be selected using the checkbox on the left and selected with Select.

In both cases, the dialog needs to be confirmed with OK.

From this point, the DLL can be addressed as follows:

The DLL used in the example looks as follows: 

Info in MSDN:

How to sign an Assembly
http://msdn.microsoft.com/en-us/library/ms247123(v=vs.90).aspx

How to install an Assembly into the Global Assembly Cache
http://msdn.microsoft.com/en-us/library/dkkx7f79.aspx