Here's my code:

        void gkh_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == neededLetter as Keys)
            {
                if (neededLetter == "n")
                {
                    neededLetter = "o";
                }
                else if (neededLetter == "o")
                {
                    neededLetter = "t";
                }
                else if (neededLetter == "t")
                {
                    neededLetter = "e";
                }
                else if (neededLetter == "e")
                {
                    this.Show();
                }
            }
            else
            { 
                neededLetter = "n";
            }
        }

I'm getting an error on the first If block:

The as operator must be used with a reference type or nullable type