Problem using DHTMLX assembly in a .net project

I try to verify if I can use DHTMLX Scheduler for .Net in my project.
I add a reference to the assembly but the project cannot be built.

I work on Visual Studio 2008 SP1 and .Net 3.5.
I have a the following warning :
Resolved file has a bad image, no metadata, or is otherwise inaccessible. Could not load file or assembly DHTMLX.dll or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.

I think that DHMLX is compatible with .net 3.5 and Visual Studio 2008 SP.
What can I do to resolve my problem?

regular version of DHTMLX.dll is build for .Net 4.0, so you can’t attach it to .Net 3.5 project. Although, we can provide you a build for 3.5 (79.9 KB)