Quick Handling of a downloaded image to save as base 64 string, then return to original form (assumes jpg). Requires system.drawing as well as other standard using statements

ImageToBase64StringAndBack.cs

public static void GetImage_ConvertItToBase64String_ThenConvertItBack()
{

    var webClient = new WebClient();
    byte[] imageBytesRaw = webClient.DownloadData("http://www.google.com/images/logos/ps_logo2.png");

    string imageBytesAsBase64String = Convert.ToBase64String(imageBytesRaw);

    byte[] imageBytes = Convert.FromBase64String(imageBytesAsBase64String);

    //System.Drawing.Bitmap
    Bitmap bitmap;
    using (Stream bmpStream = new MemoryStream(imageBytes))
    {
        Image image = Image.FromStream(bmpStream);

        bitmap = new Bitmap(image);
    }

    bitmap.Save(@"C:\google.jpg", ImageFormat.Jpeg);

}