Nov 072006
 

I frequently store documents in the database for my ASP.NET apps, eliminating web farm complications with shared drives, permissions, etc.  When uploading a file, my Document class reads the uploaded file, zips the file with SharpZipLib, and inserts/updates in the database.   When opening a file, I have always used an ASPX page that uses the Document class to unzip the file, and then changes the Content-Disposition and ContentType headers, and then does a BinaryWrite to the Response object to display the file.


I have been using Handlers a lot lately, and figured that it was time to make this process a little more elegant.  If you’ve never written a handler, it’s quite simple.  You need to make a web.config change, and add a new class that implementts IHttpHandler.  All of the work is done in ProcessRequest.  Using the default .ashx extension for the handler eliminates the need to make any changes in IIS.  I thought about changing the handler to accept all requests with known file extensions with the document ID as the filename, like 3383.pdf.  I just figured that using the default extnesion would be easier.   Laziness or efficiency, you decide.  Check out the code.


In <system.web> in web.config:



<httpHandlers>
   
<add verb=”*” path=”DocumentHandler.ashx” type=”TestingWebApp.DocumentHandler, TestingWebApp” />
</httpHandlers>


DocumentHandler.cs:



using System;
using System.Web;

namespace TestingWebApp
{
    public class DocumentHandler : IHttpHandler
    {
        private int DocumentId
        {
            get
            {
                if(System.Web.HttpContext.Current.Request.QueryString["DocumentId"] != null && System.Web.HttpContext.Current.Request.QueryString["DocumentId"].ToString().Length > 0)
                    return Convert.ToInt32(System.Web.HttpContext.Current.Request.QueryString["DocumentId"]);
                else
                    throw new ApplicationException(“Document Handler requires a DocumentId”);
            }
        }

        #region IHttpHandler Members

        public void ProcessRequest(System.Web.HttpContext context)
        {
            context.Response.Cache.SetCacheability(HttpCacheability.Public);
            context.Response.BufferOutput = false;
            
            Document document = Document.GetDocumentByDocumentId(this.DocumentId);

            byte[] buffer = document.UnzippedBinary;
            context.Response.ContentType = document.ContentType;
            context.Response.OutputStream.Write(buffer, 0, buffer.Length);
        }

        public bool IsReusable
        {
            get { return true; }
        }

        #endregion
    }
}

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