Jon's Blog

As you probably know, you can implement caching in an ASPX page using the OutputCache directive.  However, you can't use this in an ASHX handler.  So what if you are using a handler to server binary files from the database and you want to improve peformance by using server side output caching?  You'll just need to add some of your own caching logic in your code-behind.  Here is some sample code of how you can do this.  In this very basic example we are passing the ID of our object on the query string.

// Get ID from query string
int myID = Convert.ToInt32(context.Request.QueryString["ID"]);

// Attempt to get item from cache if it exists
string myCacheKey = "MyKey" + myID; // Unique Identifier
MyObject myObject = context.Cache[myCacheKey] as MyObject;

if (myObject == null)
{
    // Item isn't cached; Grab business object from the database
    myObject = MyObject.GetMyObject(myID);

    // Add object to Cache using the cache key
    // In this example we are caching for 30 minutes
    context.Cache.Insert(myCacheKey, myObject, 
        null, DateTime.UtcNow.AddMinutes(30), 
        Cache.NoSlidingExpiration);
}

// Code to generate file from binary data here

Below is some sample code I used to resize an uploaded image if the image does not meet the required width and height.  MAX_WIDTH and MAX_HEIGHT below are constants.  Change them as needed.  I am saving the resized image as a JPEG.  It is also a good idea to inform the user that their image was resized.  I removed that code to increase readability.

Note: In this sample the image is being saved to a database, but you could also save it to a file if you wanted to.

if (fileUpload.HasFile)
{
    // Get uploaded image from upload control
    System.Drawing.Image uploadedImage = System.Drawing.Image.FromStream(fileUpload.PostedFile.InputStream);
    
    // Check width and height of image and resize if necessary
    if (uploadedImage.Width > MAX_WIDTH || uploadedImage.Height > MAX_HEIGHT)
    {
        // Get the factor we must resize by
        decimal heightFactor = Decimal.Divide(uploadedImage.Height, MAX_HEIGHT);
        decimal widthFactor = Decimal.Divide(uploadedImage.Width, MAX_WIDTH);
        decimal resizeFactor = Math.Max(heightFactor, widthFactor);

        // Calculate the new height and width using the resize factor
        int newHeight = Convert.ToInt32(uploadedImage.Height / resizeFactor);
        int newWidth = Convert.ToInt32(uploadedImage.Width / resizeFactor);

        Bitmap sourceBitmap = new Bitmap(uploadedImage);
        Bitmap newBitmap = new Bitmap(newWidth, newHeight);
        Graphics graphics = Graphics.FromImage(newBitmap);
        MemoryStream memoryStream = new MemoryStream();

        try
        {
            // Set quality settings and save to MemoryStream object as Jpeg
            graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
            graphics.CompositingQuality = CompositingQuality.HighQuality;
            graphics.SmoothingMode = SmoothingMode.HighQuality;
            graphics.DrawImage(sourceBitmap, new Rectangle(0, 0, newWidth, newHeight));
            newBitmap.Save(memoryStream, ImageFormat.Jpeg);

            // Save to Business Object
            bizObject.FileData = new Binary(memoryStream.ToArray());
            bizObject.FileType = "image/jpeg";
            bizObject.FileName = Path.GetFileNameWithoutExtension(fileUpload.FileName) + ".jpg";
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            // Dispose of graphics objects
            memoryStream.Dispose();
            sourceBitmap.Dispose();
            newBitmap.Dispose();
            graphics.Dispose();
        }
    }
    else
    {
        // Image size is correct, so save what was uploaded
        bizObject.FileType = fileUpload.PostedFile.ContentType;
        bizObject.FileName = fileUpload.FileName;
        bizObject.FileData = new Binary(fileUpload.FileBytes);
    }
    
    // Other code removed for clarity
}