Refer to Part 1 for the initial problem & requirements:
The Goal:
DevExpress API is a solid one. I thought it would be beneficial to understand how resources work inside-out. This knowledge will help you while troubleshooting issues with resource loading when you use DevExpress controls in your application.
Main Components:
The assembly file DevExpress.Web.dll adds
handler DevExpress.Web.ASPxHttpHandlerModule at 'DX.Ashx' path to handle any
http request that contains the request "dxr.axd?….".
To check from IIS:
To check from web.config:
<add type="DevExpress.Web.ASPxClasses.ASPxHttpHandlerModule,
DevExpress.Web.v12.2, Version=12.2.13.0, Culture=neutral,
PublicKeyToken=b88d1754d700e49a" verb="GET" path="DX.ashx" validate="false" />
How it works:
Note: For simplicity I am only talking about
single resource request here. Comma-separated multiple resources can be
requested also.
1. When a DevExpress
dll is loaded, it will reference the resources it holds. For example the
DevExpress.Web.v12.2.dll
contains this image file "Images.GridView.sprite.png".
This resource among others was loaded into internal resource storage collection
when all assemblies were loaded. Each resource will be added to a dictionary
collection and to be given an
index value equal to total resources added already. In this case, the image was added at resource index of 45.
2. User navigates to a page that has a DevExpress UI control (ex: ASPxClientGridView) which contains an image resource (the grouping '+' icons) among others.
https://{SiteUrl}/../SomePage.aspx
3. Internally, the back-end code of the control inserts some js code on the front-end to call the url of the intended resource image. So the '+' icon will actually be calling this url to get content:
https://{SiteUrl}/DXR.axd?r=1_45-IZnRb
4. The request format is: DXR.axd?r={AssemblyNumber}_{ResourceIndex}-{DateToken}
Let's break it down:
- DXR stands for "DevExpressResource"
- AssemblyNumber: an integer value represents which dll has the required resource. Use below table to figure which dll should serve your resource. I used assemblies of version 12 but it should apply to other versions as well. Example: the required resource we used “r=1_45-IZnRb” has '1' as value of AssemblyNumber, so the required dll file is “DevExpress.Web.v12.2.dll”.
Assembly
Number
|
Assembly Dll
|
0
|
DevExpress.Web.ASPxThemes.v12.2.dll
|
1
|
DevExpress.Web.v12.2.dll
|
2
|
Not used
|
3
|
Not used
|
4
|
DevExpress.Web.ASPxHtmlEditor.v12.2.dll
|
5
|
DevExpress.Web.ASPxSpellChecker.v12.2.dll
|
6
|
DevExpress.Web.ASPxTreeList.v12.2.dll
|
7
|
DevExpress.Web.ASPxPivotGrid.v12.2.dll
|
8
|
DevExpress.Web.ASPxScheduler.v12.2.dll
|
9
|
DevExpress.XtraReports.v12.2.Web.dll
|
10
|
DevExpress.XtraCharts.v12.2.Web.dll
|
11
|
DevExpress.Web.ASPxGauges.v12.2.dll
|
12
|
DevExpress.PivotGrid.v12.2.Core.dll
|
13
|
DevExpress.ExpressApp.Web.v12.2.dll
|
14
|
DevExpress.Web.Mvc.v12.2.dll
|
15
|
DevExpress.XtraDashboard.v12.2.Web.dll
|
- ResourceIndex: a positive integer value represents the index of a specific resource inside assembly.
- DateToken: a string value of Base64 representation of last modified date of the resource or the assembly file.
5. When a resource request received, the custom
handler module will process http request get the required resource via a
resource manager if the http request path ends with “Dxr.axd” string. Only the
portion before ‘-‘ is considered, so only the “r=1_45” part is to be processed
& resolved to get the corresponding resource image if available. The date
token will not be part of this.
6. So the resource manager will pass values of ‘1’ which will resolve into full dll name ‘DevExpress.Web.v12.2, Version=12.2.13.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a’ Key And pass the number '45' as a resource number, then the dictionary value is "DevExpress.Web.Images.GridView.sprite.png"
7. Then it will get the binary content of that resource file & put it in http response to be displayed in the control in page
8. If you want to test the resource directly, you can type the url for it:
https://{SiteUrl}/DXR.axd?r=1_45-IZnRb
Notes:
- All of these resource images will be saved as "DXR.png" when downloaded from IE.
- I found this config key "DXResourcesPhysicalPath". If it has content then it can be used internally to get resource path.
- Another key to compress binary resources before returning them in http response. <add key="DXEnableResourceCompression" value="true"/>
- There are other config keys that play a role in data compression
& increased performance: <add
key="DXEnableCallbackCompression" value="true"/>
<add key="DXEnableResourceMerging" value="true"/>
