jrafaelm wrote:

I have installed Framework 3.5 sp1

I really know nothing about VB.NET. But what I've found about it, I believe that VB.NET 2003 does not support .NET 3.5, not matter if you have it installed or not.

How I use it directly as an assembly? Sorry. I do not understand

Again, I really know nothing about VB.NET. In C#, the difference would be between adding "Reference to an assembly" to the project or "Reference to COM library". WinSCP .NET assembly is both, but you cannot reference COM library that is also .NET assembly from .NET project.

I have installed Framework 3.5 sp1
How I use it directly as an assembly? Sorry. I do not understand

Or, from the error message, it actually looks like you might be adding the assembly as COM library. AFAIK, you cannot reference COM interface of .NET assembly from another .NET assembly. You need to use it directly as an assembly.

Ok. I do not have any experience with Visual Basic .NET 2003. But I've found that is uses .NET Framework 1.1. While WinSCP .NET assembly needs .NET Framework 2.0. So that can be the root cause.

Yes. I followed the steps in the document. The error occurs when you add the reference to the project

Did you follow this?
https://winscp.net/eng/docs/library_install#installing

When do you get the error?

I can not add the assembly in vb.net 2003. Error: Type Library WinSCP was exported from a CLR and can not be re-imported as a CLR assembly