調整大小后無法刪除或重命名原始文件

Question

此函數返回一個調整大小並居中的圖像，我調用url thumb.aspx?image=test.jpg&width=100&height=50 對其執行 ，問題是執行后 ， 我無法從服務器重命名或刪除原始文件。

  <%@ Import Namespace="System.Drawing" %>
    <script language="C#" runat="server">
    void Page_Load(Object sender, EventArgs e) {
      try {
        Response.Cache.VaryByParams["Image;Width;Height;needToFill"] = true;
        Response.ContentType = "image/jpeg";
        System.Collections.Hashtable imageOutputFormatsTable = new System.Collections.Hashtable();
        imageOutputFormatsTable.Add(System.Drawing.Imaging.ImageFormat.Gif.Guid, System.Drawing.Imaging.ImageFormat.Gif);
        imageOutputFormatsTable.Add(System.Drawing.Imaging.ImageFormat.Jpeg.Guid, System.Drawing.Imaging.ImageFormat.Jpeg);
        imageOutputFormatsTable.Add(System.Drawing.Imaging.ImageFormat.Bmp.Guid, System.Drawing.Imaging.ImageFormat.Gif);
        imageOutputFormatsTable.Add(System.Drawing.Imaging.ImageFormat.Tiff.Guid, System.Drawing.Imaging.ImageFormat.Jpeg);
        imageOutputFormatsTable.Add(System.Drawing.Imaging.ImageFormat.Png.Guid, System.Drawing.Imaging.ImageFormat.Jpeg);
        string imageLocation = Server.MapPath(Request.QueryString["Image"]);
        int Width = Convert.ToInt32(Request.QueryString["Width"]);
        int Height = Convert.ToInt32(Request.QueryString["Height"]);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(imageLocation);
        int sourceWidth = image.Width;
        int sourceHeight = image.Height;
        int sourceX = 0;
        int sourceY = 0;
        double destX = 0;
        double destY = 0;
        double nScale = 0;
        double nScaleW = 0;
        double nScaleH = 0;
        bool needToFill=true;
        nScaleW = ((double)Width / (double)sourceWidth);
        nScaleH = ((double)Height / (double)sourceHeight);

        if (Request.QueryString["needToFill"] != null) {
            needToFill = Convert.ToBoolean(Request.QueryString["needToFill"]);
        }

        if (!needToFill) {
            nScale = Math.Min(nScaleH, nScaleW);
        } else {
            nScale = Math.Max(nScaleH, nScaleW);
            destY = (Height - sourceHeight * nScale) / 2;
            destX = (Width - sourceWidth * nScale) / 2;
        }

        if (nScale > 1) nScale = 1;

        int destWidth = (int)Math.Round(sourceWidth * nScale);
        int destHeight = (int)Math.Round(sourceHeight * nScale);

        System.Drawing.Bitmap bmPhoto = new System.Drawing.Bitmap(destWidth + (int)Math.Round(2 * destX), destHeight + (int)Math.Round(2 * destY));
        bmPhoto.SetResolution(72, 72);
        System.Drawing.Imaging.ImageFormat outputFormat = (System.Drawing.Imaging.ImageFormat)imageOutputFormatsTable[image.RawFormat.Guid];
        ApplicationException ex= new ApplicationException(string.Format("destWidth:{0}, destX:{1}, destHeight:{2}, desxtY:{3}, Width:{4}, Height:{5}", destWidth, destX, destHeight, destY, Width, Height));
        System.Drawing.Graphics grPhoto = System.Drawing.Graphics.FromImage(bmPhoto);
        Rectangle to =  new System.Drawing.Rectangle((int)Math.Round(destX), (int)Math.Round(destY), destWidth, destHeight);
        Rectangle from = new System.Drawing.Rectangle(sourceX, sourceY, sourceWidth, sourceHeight);
        grPhoto.DrawImage(image, to, from, System.Drawing.GraphicsUnit.Pixel);

        bmPhoto.Save(Response.OutputStream, outputFormat);
        bmPhoto.Dispose();
        grPhoto.Dispose();
      }
      catch (Exception ex){
        System.IO.StreamWriter sw=null;
        try{
            sw=new System.IO.StreamWriter(Server.MapPath("error.txt"),true);
            sw.WriteLine("Error : " + ex.Message + " processing " + Request.QueryString["Image"]);
        }    
        catch{}     
        finally{sw.Close();}
        Response.Redirect("thumberror.gif");
      }
    }
    </script>

Answer 1

image看起來好像沒有被處理。 我建議使用using語句使資源管理更加清晰。

using語句允許在范圍內放置一些東西，當離開范圍時，將在其上調用Dispose 。 例如：

using(var image = new Bitmap(imageLocation))
{
    //Use image here
} //image will be disposed here