non-static member of outer type

[vivendi]

Hey, i get the following error when i try to compile my project:

Cannot access a non-static member of outer type 'Project.Shader' via nested type 'Project.Shader.RenderSurfaceSet'.

What i'm doing is the following.
I have a class called worldView.cs, in that class i create the Shader class like so:

[Inside worldView.cs]

Shader shader = new Shader(this);

As you can see a pass an instance of the worldView class to the shader class. The shader class uses some variabled declared in the worldView class without a problem.
But here comes the issue:

In the Shader.cs class i also have a struct defined inside the class, like so:

    public class Shader
    {
        public View.WorldView world;

        RenderSurfaceSet[] downscaledSets;

        public Shader(View.WorldView world)
        {
            this.world = world;
            Initialize();
        }

        //some functions inside the class

        //the struct
        struct RenderSurfaceSet
        {
            //some variables here

            public RenderSurfaceSet(int downscalingFactor, int sourceTexture)
            {
                //code in constrcutor
            }
            //and some other functions inside this struct
        }
}

Now what i'm trying to do is also use the worldView instance inside this struct. The worldView object seems to be accessible from within that struct, but when i try to compile it it generates that error.

Anyone any idea how to solve that??