Month February 2013

Lunch Time – An MVP Community Initiative

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Lunch Time is a new talk series scheduled on every alternate Wednesday during the Lunch Time, initiated and will be presented by the Microsoft Most Valuable Professionals.
Current schedule:

Date/TimeTopic
Mar 06, 2013, 12:00 PM ISTGood things about .NET 4.5
Mar 20, 2013, 12:00 PM ISTASP.NET 4.5 New Features
Apr 03, 2013, 12:00 PM ISTBuilding Site Resiliency for Exchange 2013
Apr 17, 2013, 12:00 PM ISTResponsive Apps with MVC4, WebAPI and HTML5
May 01, 2013, 12:00 PM ISTA Quick Look at HTML5
May 15, 2013, 12:00 PM ISTImplementing SQL Server AlwaysOn

Across the globe, anyone can join in and learn from technical community leaders.

I will be presenting one of the session in this series – A Quick Look at HTML5 (Event ID: 1032545489)
Sandeep Mewara LunchTime Microsoft Event 01May13
Please register! Do share your feedback post presentation.

Developer Day, Bangalore 23 February 2013

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PanelDiscussion23Feb13


HelloWorldGeeks.com cordially invites to Developer Day, the quarterly dose of Microsoft Developer Technologies knowledge & learning.

They bring one focussed session on Hyper-V in Windows 8 for Developers by Vijay Raj (MVP) and a panel discussion led by Amit Bansal. Apart from Amit, panelists will include real-life developer heroes Vijay Raj, Niral Bhatt & Sandeep Mewara , all MVPs.

You have the opportunity to ask any .NET/developer related question to them. Event will be hosted in Microsoft premises in Bangalore so that your experience is fabulous.

For details and registration, please visit: Developer Day

HTML5 Quick Start Web Application

smewara 1 Comment
HTML5 Quick Start


I was learning HTML5 features since December. While going through it, I was playing around making a sample web application fully HTML5 enabled – kind of self learning kit that would give a basic knowledge to anyone who goes through it. Plan was to publish it as an article so that others can learn quickly and have basic features at one place. One can play around with the feature implementation straight away post download.

It took me some time to write the article as it covered good number of features. I finished working on it and have published it today on CodeProject: HTML5 Quick Start Web Application

One can have a look at it there and provide feedback.

UPDATE: Missed uploading this to Github earlier, uploaded here: https://github.com/sandeep-mewara/HTML5QuickStart

Keep learning!

HTTP 500 – Internal server error

smewara 1 Comment

This is another common error that troubles a lot of ASP.NET users.

Problem Statement

Generally, the questions are framed like:

I receive a HTTP 500 – Internal Server Error  exception while trying to browse my hosted web application. Exception message says “This error (HTTP 500 Internal Server Error) means that the website you are visiting had a server problem which prevented the webpage from displaying”. Please help, how to resolve it?

Assessment

Any HTTP request made to web application running on IIS (or any other web server) returns the status of the response. This HTTP status code indicates about the request success or failure. If the request was unsuccessful, it might provide the reason why so.

Out of various status code, 5xx are the codes related to Server error. They indicate that the server failed to complete the request because server encountered an error.

The 500 Internal Server Error is a very general HTTP status code. It means something has gone wrong on the website and web server is unable to specify what exactly, thus failing in fulfilling the request made by the client. This is not related to client and the fault is in the webpage/website requested that resides on server. This status code can be considered as a ‘catch-all’ server error of Web server.

More details around various HTTP status code: The HTTP status code in IIS 7.0, IIS 7.5, and IIS 8.0

Possible Resolutions

Make sure that internally web server maintains some kind of internal error logs that gives more detail of what went wrong and thus help in diagnosing the issue. Generally, it is logged into Windows Event Logs on the server. Thus, first thing while troubleshooting the error is to see Windows Event Logs on the server to find what went wrong.

Other useful thing to troubleshoot it would be to disable friendly HTTP error messages to see if the raw content can provide a direction to look more. Steps:

  • Go to menu Tools/Internet Options in your IE.
  • Click on the Advanced tab & then uncheck “Show friendly HTTP error messages” option & then click Ok.
  • Now, when on accessing the same web page, much more developer meaningful error message will be shown.

Moving on, following are most common:

Option #1:
HRESULT: 0x80070035 – The page cannot be displayed because an internal server error has occurred.
This occurs because the server that is running IIS cannot access the configured root directory of the requested location.

Resolution would be to make sure that the server that is running IIS can access the configured root directory of the requested location.

Option #2:
HRESULT: 0x800700c1 – The page cannot be displayed because an internal server error has occurred.
This occurs because a script mapping is not valid.

Resolution would be to make sure that the script mapping points to the ISAPI.dll file that can process the request.
To do this, follow these steps:

  1. Click Start, click Run, type inetmgr.exe, and then click OK.
  2. In IIS Manager, expand server name, expand Web sites, and then click the Web site that you want to modify.
  3. In Features view, double-click Handler Mappings.
  4. Make sure that the script mapping points to the correct ISAPI.dll file. (e.g: .asp files should map to the %windir%\system32\inetsrv\asp.dll file)

Option #3:
HRESULT: 0x8007007f – There is a problem with the resource you are looking for, so it cannot be displayed.
This occurs because the handler mapping for the requested resource points to a .dll file that cannot process the request.

Resolution would be to edit the handler mapping for the requested resource to point to the .dll file that can process the request.
To do this, follow these steps:

  1. Click Start, click Run, type inetmgr.exe, and then click OK.
  2. In IIS Manager, expand server name, expand Web sites, and then click the Web site that you want to modify.
  3. In Features view, double-click Handler Mappings.
  4. Right-click the script mapping that you want to edit, and then click Edit.
  5. In the Edit Script Map dialog box, type the appropriate executable file in the Executable box, and then click OK.

Option #4:
One of the other possibilities could be an issue in the way web application is hosted. Some security configuration issue or conflict due to multiple config files.

Resolution would be to make sure application is hosted correctly by published the application as website and setting up the virtual directory as needed.
More details around the known issues and their resolution:
Error message when you visit a Web site that is hosted on IIS 7.0: “HTTP Error 500.0 – Internal Server Error”
Troubleshoot an “HTTP 500 – Internal Server Error” error message on IIS 4.0 or on IIS 5.0

Conclusion

This is a server error and can only be solved by website admin who has access to files and the web-server. There can be one of/or multiple reasons to get this error. One has to track down the issue and handle accordingly.

Keep learning!

Extract node from XML having defined namespace using XPath in C#

smewara 1 Comment

At work, while working on one of the features, we had to get a specific node from an XML. Obvious choice was to use XPath.

Problem Statement

Ignoring specifics of XML, we directly put the XPath as expected and found that no node was found when we executed the path.
I had to look up on how to extract the deep embedded node we needed using XPath in such case.

Assessment

We observed that the elements/nodes are bound to a namespace. When we tried the direct XPath, it was attempting to address elements that are bound to the default “no namespace” namespace, and thus nothing was retrieved.
Sample XML to work with:

<?xml version="1.0"?>
<SampleXmlRoot xmlns="http://www.samplesite.com/example/SampleXmlRoot">
<SampleXmlSubRoot someValue="21" xmlns="http://www.samplesite.com/example/SampleXmlSubRoot">
<SampleXmlLevel2Node id="101" xmlns="http://www.samplesite.com/example/SampleXmlLevel2Node">
<SampleXmlNode2Extract num="2">
<A1 type="money">
<value>1234.0</value>
</A1>
<A2 type="money">
<value>123.4</value>
</A2>
<A3 type="money">
<value>12.3</value>
</A3>
</SampleXmlNode2Extract>
<SampleXmlNodeOther num="2">
<B1 type="money">
<value>234.0</value>
</B1>
<B2 type="money">
<value>23.4</value>
</B2>
</SampleXmlNodeOther>
</SampleXmlLevel2Node>
</SampleXmlSubRoot>
</SampleXmlRoot>


Based on what we observed and a quick reference, we learned that we need to register the namespace for namespace prefix mapping that will be used in defining the XPath.

Using XmlNamespaceManager object, we can provide a collection of namespace definitions that will be  used by CLR to resolve the elements used in the XML documents.

Resolution

Step 1: Define XmlNamespaceManager

// xmlDoc is XmlDocument in which full XML is loaded
XmlNamespaceManager xmlnsManager = new XmlNamespaceManager(xmlDoc.NameTable);

// Add the namespaces used in XML to the XmlNamespaceManager
xmlnsManager.AddNamespace("sxr", "http://www.samplesite.com/example/SampleXmlRoot");
xmlnsManager.AddNamespace("sxsr", "http://www.samplesite.com/example/SampleXmlSubRoot");
xmlnsManager.AddNamespace("sxl2", "http://www.samplesite.com/example/SampleXmlLevel2Node");


Step 2: Use select method that is overloaded to use XmlNamespaceManager along with XPath
In our case, we will select the first XmlNode that matches the XPath expression where any prefixes found in the XPath expression will be resolved using the supplied XmlNamespaceManager.

String xPath = "/sxr:SampleXmlRoot/sxsr:SampleXmlSubRoot/sxl2:SampleXmlLevel2Node/SampleXmlNode2Extract";
XmlNode extractedNode = xDoc.SelectSingleNode(xPath, xmlnsManager);


XmlNode extracted OuterXml will look something like:

<SampleXmlNode2Extract num="2">
<A1 type="money">
<value>1234.0</value>
</A1>
<A2 type="money">
<value>123.4</value>
</A2>
<A3 type="money">
<value>12.3</value>
</A3>
</SampleXmlNode2Extract>

Yep, that’s the exact one we needed!

Refer:
MSDN: XmlNamespaceManager Class
MSDN: XmlNode.SelectSingleNode Method (String, XmlNamespaceManager)

Conclusion

XPath is a wonderful way to extract node(s) and we have defined methods in place to get them. We just need to know and learn about them. XmlNamespaceManager handles the namespace and helps in defining the XPath for a given XML.