[转载]ASP.NET MVC3 20个秘方-（12）改变图片的大小生成缩略图

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Web;
using System.IO;

namespace MvcApplication.Utils
{
    public static class FileUpload
    {
        public static char DirSeparator = Path.DirectorySeparatorChar;
        public static string FilesPath = HttpContext.Current.Server.MapPath(string.Format("Content{0}Uploads{1}", DirSeparator, DirSeparator));
        public static string UploadFile(HttpPostedFileBase file)
        {
            // Check if we have a file
            if (null == file) return "";
            // Make sure the file has content
            if (!(file.ContentLength > 0)) return "";
            string fileName = file.FileName;
            string fileExt = Path.GetExtension(file.FileName);
            // Make sure we were able to determine a proper
            // extension
            if (null == fileExt) return "";
            // Check if the directory we are saving to exists
            if (!Directory.Exists(FilesPath))
            {
                // If it doesn't exist, create the directory
                Directory.CreateDirectory(FilesPath);
            }
            // Set our full path for saving
            string path = FilesPath + DirSeparator + fileName;
            // Save our file
            file.SaveAs(Path.GetFullPath(path));
            // Save our thumbnail as well
            ResizeImage(file, 150, 100);
            // Return the filename
            return fileName;
        }
        public static void DeleteFile(string fileName)
        {
            // Don't do anything if there is no name
            if (fileName.Length == 0) return;
            // Set our full path for deleting
            string path = FilesPath + DirSeparator + fileName;
            string thumbPath = FilesPath + DirSeparator +
            "Thumbnails" + DirSeparator + fileName;
            RemoveFile(path);
            RemoveFile(thumbPath);
        }
        private static void RemoveFile(string path)
        {
            // Check if our file exists
            if (File.Exists(Path.GetFullPath(path)))
            {
                // Delete our file
                File.Delete(Path.GetFullPath(path));
            }
        }
        public static void ResizeImage(HttpPostedFileBase file, int width, int height)
        {

            string thumbnailDirectory =
            String.Format(@"{0}{1}{2}", FilesPath,
            DirSeparator, "Thumbnails");
            // Check if the directory we are saving to exists
            if (!Directory.Exists(thumbnailDirectory))
            {
                // If it doesn't exist, create the directory
                Directory.CreateDirectory(thumbnailDirectory);
            }
            // Final path we will save our thumbnail
            string imagePath =
            String.Format(@"{0}{1}{2}", thumbnailDirectory,
            DirSeparator, file.FileName);
            // Create a stream to save the file to when we're
            // done resizing
            FileStream stream = new FileStream(Path.GetFullPath(
            imagePath), FileMode.OpenOrCreate);
            // Convert our uploaded file to an image
            Image OrigImage = Image.FromStream(file.InputStream);
            // Create a new bitmap with the size of our
            // thumbnail
            Bitmap TempBitmap = new Bitmap(width, height);
            // Create a new image that contains quality
            // information
            Graphics NewImage = Graphics.FromImage(TempBitmap);
            NewImage.CompositingQuality =
            CompositingQuality.HighQuality;
            NewImage.SmoothingMode =
            SmoothingMode.HighQuality;
            NewImage.InterpolationMode =
            InterpolationMode.HighQualityBicubic;
            // Create a rectangle and draw the image
            Rectangle imageRectangle = new Rectangle(0, 0,
            width, height);
            NewImage.DrawImage(OrigImage, imageRectangle);
            // Save the final file
            TempBitmap.Save(stream, OrigImage.RawFormat);
            // Clean up the resources
            NewImage.Dispose();
            TempBitmap.Dispose();
            OrigImage.Dispose();
            stream.Close();
            stream.Dispose();
        }
    }
}