CSS gradient on C#

CSS gradient on C# using CityLizard Framework. Works in IE 5.5-8.0, FireFox 3.6, Chrome 8.0, Safari 5.0 and Opera 10.

namespace Css
{
    using S = www_w3_org._2000.svg.X;
    using D = System.Drawing;

    class Gradient
    {
        class Svg : S
        {
            public T.svg Gradient(string start, string end)
            {
                return
                    svg_(width: "100%", height: "100%")
                        [defs
                            [linearGradient_(
                                id: "grad",
                                x1: "0",
                                y1: "0",
                                x2: "0",
                                y2: "100%")
                                [stop_(offset: "0", stop_color: start)]
                                [stop_(offset: "1", stop_color: end)]
                            ]
                        ]
                        [rect_(
                            width: "100%",
                            height: "100%",
                            x: "0",
                            y: "0",
                            style: "fill:url(#grad)")
                        ];
            }
        }

        static string X2(byte x)
        {
            return x.ToString("X2");
        }

        static string ToString(D.Color c)
        {
            return "#" + X2(c.R) + X2(c.G) + X2(c.B);
        }

        static byte Avg(byte a, byte b)
        {
            return (byte)((a + b) / 2);
        }

        static D.Color Avg(D.Color a, D.Color b)
        {
            return D.Color.FromArgb(
                Avg(a.R, b.R), Avg(a.G, b.G), Avg(a.B, b.B));
        }

        public static string Y(D.Color Start, D.Color End)
        {
            var s = ToString(Start);
            var e = ToString(End);
            var svgB = new Svg().Gradient(s, e).ToString();
            var svg = "";
            foreach (var c in svgB)
            {
                var x = (int)c;
                if (x <= 0x40)
                {
                    svg += "%" + x.ToString("X2");
                }
                else
                {
                    svg += c;
                }
            }
            // Next browsers to test: Opera 11 (hopefully it has CSS gradient), 
            // IE 9.
            return
                // for other browsers.
                "background: " + ToString(Avg(Start, End)) + ";" +

                // Opera 10. It also works for Chrome and Safari.
                "background: url(\"data:image/svg+xml," + svg + "\");" +

                // IE 5.5-8.0.
                "filter: progid:DXImageTransform.Microsoft.gradient(" +
                "startColorstr='" +
                s +
                "', endColorstr='" +
                e +
                "');" +

                // webkit browsers (Chrome, Safari). It is not required 
                // because SVG gradient for Opera works fine for these 
                // browsers.
                /*
                "background: -webkit-gradient(" +
                "linear, left top, left bottom, from(" + 
                s + 
                "), to(" + 
                e + 
                "));" +
                */

                // FireFox 3.6+
                "background: -moz-linear-gradient(top,  " + s + ", " + e + ");";
        }
    }
}