2016-09-20

I've recently taken a fancy to learning about ASP.NET Charts. I've built two bar charts --
one basic one and one with some bells and whistles. 

There's a lot of configuration involved with using the UI.DataVisualization.Charting namespace.
I'd never call myself an expert, but I'm happy to share with you what I've learned and
where I've learned it.

Grab some coffee before we dive into the world of...


CONFIGURATION: WEB.CONFIG


Happily, if you use the actual drag-and-drop method from the Visual Studio toolbox, the IDE 
will make the configuration changes for you:

	When you drag a Chart control from the Toolbox onto the design surface of the 
	ASP.NET page, the ChartHttpHandler is automatically registered in the Web.config 
	file as "ChartImageHandler". You can configure ChartImageHandler's behavior in 
	the <appSettings> element. (1)

By the way, I prefer writing the code. I know it takes the "Visual" out of "Visual Studio",
but at least in the past the designer would add all kinds of unnecessary code to your 
project. BUT -- the addition of all of the following Web.Config goop for you is pretty nice.

The Web.Config edits occur in multiple places (and these are edits to your root Web.Config, not a Web.Config in your 
current directory if you have one): 

(1) Configuration/AppSettings

    <appSettings>
      <add key="ChartImageHandler" value="storage=session;timeout=1;" />
    </appSettings>

(2) Configuration/System.Web/Compilation/Assemblies

    <compilation debug="true" strict="false" explicit="true" targetFramework="4.5">
      <assemblies>
        <add assembly="System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
      </assemblies>
    </compilation>

(3) Configuration/System.Web/Pages/Controls

    <pages>	
      <controls>
        <add tagPrefix="asp" namespace="System.Web.UI.DataVisualization.Charting" assembly="System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
      </controls>
    </pages>

(4) Configuration/System.Web/Httphandlers
    
    <httpHandlers>
      <add path="ChartImg.axd" verb="GET,HEAD,POST" type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler,
System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, 
PublicKeyToken=31bf3856ad364e35" validate="false" />
    </httpHandlers>

These values are straight from my local Web.Config. My solution started as a .NET 3.5 
solution and was upgraded to 4.5. Your mileage may vary.


CONFIGURATION: THE CHART IMAGE HANDLER


(1) Security Environment
    
The configuration of the Chart Image Handler in <appSettings> is especially important.
The link in footnote (1) goes into detail about how to configure the handler for the
security environment your server operates in. This site, for example, is in a shared
hosting environment operating with low or minimal trust. 

(2) Storage

Because my production site runs in low or minimal trust, So my only storage option is
session (as opposed to file). If you operate in a higher trust environment, then
storage in a file or in memory are also options for you. The example in footnote (1)
shows the handler configured for file storage, and includes a directory path.

(3) Timeout

The default value for the amount of time before the image file can be replaced is
30 seconds. I reduced that timeout value during development.

(4) Dir

absolute path for image storage if you're using the file storage option. This argument
is not necessary if you're using session storage instead.


CONFIGURATION: THE CHART CONTROL


A number of the Web.config settings can be set directly on the chart control. 
For example, the storage option indicated in the image handler can also be set as
the ImageStorageMode property. Configuring these properties directly on the control
will allow for more granular control. I believe properties settings on the control
will override the Web.Config settings.


That should be it for now! Contact me using the site's contact form if 
you have questions. Feel free to use the code in your projects. A shout
out in your project would be thoughtful. Also, drop me a line and let me
know how you might have tweaked things to better suit your needs. 
Finally, I wouldn't profess to be THE expert on matters represented in
my code -- so drop me a line if you have constructive suggestions, too. 
I'd like to hear from you!
  

Best,

halfgk



(1) "Image File Management", Microsoft Corporation. Accessed 9/20/2016 from
https://msdn.microsoft.com/en-us/library/dd456629.aspx



Copyright 2016 halfgk.com