asp上传视频后怎么生成缩略图啊

/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="fileName">原文件</param>
/// <param name="width">宽度</param>
/// <param name="height">高度</param>
private void CreateThumbnailImage(string fileName, string smallPath, int width, int height)
{
//版权信息
string strAdd = "www.wander.com";
//生成的缩略图的名字=年月日+文件大小(防止文件名相同)
string newFileName = smallPath;

System.Drawing.Image image, newImage;
//载入原图像
image = System.Drawing.Image.FromFile(Server.MapPath(fileName));
//回调
System.Drawing.Image.GetThumbnailImageAbort callb = new System.Drawing.Image.GetThumbnailImageAbort(callBack);
//生成缩略图
newImage = image.GetThumbnailImage(width