InvalidCastException? Are you sure? Why?

I've created a class here for a ColumnHeader:

public class ColHeader : ColumnHeader
{
    public bool ascending;
    public ColHeader(string text, int width, HorizontalAlignment align, bool asc)
    {
        this.Text = text;
        this.Width = width;
        this.TextAlign = align;
        this.ascending = asc;
    }
}

And when I say this:

ColHeader clickedCol = (ColHeader)this.listView1.Columns[e.Column];

It says I can't convert the ColHeader class into a ListView.ColumnHeader. Why is this? I'm just starting to learn classes so I don't really understand.

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“It is not that I'm so smart. But I stay with the questions much longer.” ― Albert Einstein