FileNotFoundException: Could not load file or assembly 'OCCTProxy.DLL'

Hello, I'm getting FileNotFoundException: Could not load file or assembly 'OCCTProxy.DLL' when trying to run the samples. When OCCTProxy object should be created.

I read the internet that it happens when some required .dll's are missing. So I downloaded the dependency walker and it showed me that I'm missing only windows 7 related .dll's (which should be ignored if believ information from the internet).

Help me solve this problem.

I'm trying to run samples on Windows 10, VS 2017.

Guido van Hilst not specified's picture

Hi Gov,

Are you sure that all dll's ( including external libraries) are in the exe path?

Also is best to set the CASROOT variable to the occ path, because visualization and other object may require to find shaders and units.

Best regards,


If you are looking for solution to develop OpenCascade in C#/.Net:

I have developed advanced C# wrappers to opencascade.

A number of helper-libraries make it very easy to use opencascade in C#. For example, there are extension methods that make it easy to iterate directly over edges and faces, or other entities, of a TopoDS_shape.

Example: foreach(TopoDS_Edge e in shape.Edges())

Also direct access to the underlying geometry is easy. Example:
face.Surface () or edge.Curve ();
Dynamic casting makes it easy to get the right type of geometry.
Example: Geom_Plane plane = face.Surface () as Geom_Plane;

There a 6 assemblies for each occ module:

  • CCT.OCDotNet.Foundation.dll
  • CCT.OCDotNet.ModelingData.dll
  • CCT.OCDotNet.ModelingAlgorithms.dll
  • CCT.OCDotNet.Visualization.dll
  • CCT.OCDotNet.ApplicationFramework.dll
  • CCT.OCDotNet.DataExchange.dll

No more hassle with header files, unresolved link errors, just a ref to the assemblies.

All the help doxygen in the c++ code is availbale in Visual studio.
If you are interested in development with open cascade on platform, please contact me at

I have made an web-application that uses the wrapper libraries on the backend: You can have a look here: MakeBottle

Susheel kumar's picture

i am facing this problem in opencascade when i am executing drawexe filethe CASROOT variable is mandatory to Run OpenCascade
No default file