How to create a Floating Parameter?

I would like to create a Floating Parameter for my Grasshopper Plug-in, like the Bool parameter in the image below.

Following the guidelines here and related pages I have the following classes:

class Bar // My base class doing all sorts of things, can be used in other applications as well

class BarDataType : GH_Goospan style="color: #33cccc;">Bar> // Ensure we have Grasshopper compatibility of the Bar class

class BarParamater : GH_Paramspan style="color: #33cccc;">BarDataType>

{

    public BarParameter() : base(

        "Bar", "Bar", "Bar parameter", "MyTab", "Parameters", GH_ParamAccess.item)
    { }

    protected override System.Drawing.Bitmap Icon
    {
        get
        {
            return Resources.BarParameterIcon;
        }
    }

}

I was then expecting the Bar parameter to appear in MyTab under Parameters when debgging, but noting appears.

Do I need to create a GH_Component in order for that to happen? And if so, how do I make it appear as the floating Bool parameter?