How can ues HTMLEncode

 cmd.Parameters.Add("@e6", SqlDbType.VarChar, 0).Value = HttpUtility.HtmlEncode(TextBox6.Text);
            cmd.Parameters.Add("@e7", SqlDbType.VarChar, 0).Value = HttpUtility.HtmlEncode(TextBox7.Text);
            cmd.Parameters.Add("@e8", SqlDbType.VarChar, 0).Value = HttpUtility.HtmlEncode(TextBox8.Text);
            cmd.Parameters.Add("@e9", SqlDbType.VarChar, 0).Value = HttpUtility.HtmlEncode(TextBox9.Text);