SharePoint error: “Cannot import Web Part”

Question

I have a web part that I\'ve developed, and if I manually install the web part it is fine.

However when I have packaged the web part following the instructions on this w

Answer 1

I got this error when I created a base class web part and then inherited a derived class from it. The base class was fine but the derived class failed when I tried to add it to a web page with the same error as the original post. In my case I had to add a public modifier to the class:

public class DerivedWebPart : BaseWebPart

Also I added a constructor in the derived class to call the base class one - although I think you shouldn't need this really:

    public DerivedWebPart() : base()
    {
    }