Beware of AJAX update panel

A, "why I didn't see that before?", popped into my head thanks to:

http://encosia.com/2007/07/11/why-aspnet-ajax-updatepanels-are-dangerous/

He discusses the concept of the Update Panel. When you are doing a simple update inside the panel, you have to remember that it acts like a refresh but only returning the necessary data to that panel. This is obviously a huge load on the server.

Instead try using the web service method with the AJAX library to get a cleaner result.

I'm more of the old school ASP.Net 2.0 where I'm use to the asynccallback method. In thinking that the update panel was a simpler, quicker solution was nice though, but this just makes more sense.

Some Interview Questions given to me in the past.

1. What is a PostBack?
2. What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
3. Demonstrate definition of a property in a class (in c#)
4. Demonstrate populating a dropdownlist from an xml file (in c#)
5. How do you assign a static IP Address to a Windows 2003 Server?
6. Draw out what the outcome of an Inner Join, Left Outer Join and Right Outer Join would be on two tables.
7. How would you access the database connection strings from a web.config file in VS 2003 and VS 2005?
8. Where would you setup “Impersonation” and when would it be a good time to use it?
9. How many static IP Addresses can a Windows 2003 Server have?
10. A client needs a web page that collects the following: first name, last name, phone number and then pushes the data to them via email. Please provide sample code of a form that sends that data to the client.
11. Demonstrate in Asp.Net how to pull a remote user’s IP Address, Referring URL, and the [cookieid] from a user’s machine for domain [SAN].
12. Please provide an example of a time when you have ever used web services.
13. How would you go about debugging a web service SOAP Message?
14. How do you view the methods and properties of a web service within Visual Studio?















1) What is a postback?

http://www.xefteri.com/articles/show.cfm?id=18 does a nice job in explaining what a postback is, in detail.

In my own words: In a standard postback a web page, with a web form is submitted and then processed on the server-side. The server-side then updates the page on the client-side by reposting the data. This is usually seen with something similar to a page refresh. (Which is why, if you are buying something on the web, it's a good idea not to hit refresh button or it would duplicate the last sent request.)

Now with, javascript and nowadays Ajax, it isn't necessary to refresh the whole page. It is possible to just refresh a certain control, allowing the user to see updated information without refreshing and redrawing other controls.



2) What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?

In my own words:
A viewstate is a serializable hashtable of objects that are used to store information on the client-side. During a postback, the informatin is then used on the server-side before reposting to the client-side. This allows the data found in controls like a textbox to be repoulated, or to use the viewstate to store global variables which can be reused.

A viewstate is stored in base64, and encryption by default is set to auto. This means, as long as no control in the form does not need encryption, then the whole viewstate is unencrypted; otherwise the whole viewstate is encrypted. You can set the view state for each page:

<%@Page ViewStateEncryptionMode="Always" %>

, or you can set it for the whole website by using the web.config:

<configuration>
<system.web>
<pages ViewStateEncryptionMode="Always" />
</system.web>
</configuration>


3) Demonstrate definition of a property in a class

class MyClass
{
private string _name = “”;

public string Name
{
get
{
return _name;
}
set
{
_name = value;
}
}
}


4) Demonstrate populating a dropdownlist from an xml file


Not tested:

XML file:

<library>
<book>
<author>Dietel & Dietel</author>
<title>C how to program</title>
</book>
<book>
<author>William Shakespare</author>
</book>
</library>


XmlDocument doc = new XmlDocument();
doc.Load(Server.MapPath("Library.xml"));
XmlNodeList nodeList = doc.SelectNodes("library/book/"); //xslt path
foreach(XmlNode node in nodeList)
{
DropDownListTitle.Items.Add(new ListItem(node.SelectSingleNode("title").InnerText));
}


5) How do you assign a static IP Address to a Windows 2003 Server?

I personally don't know much about setting up servers, I'm a developer. So, I look it up:
http://technet2.microsoft.com/windowsserver/en/library/36c35b2c-8b8b-4517-812e-913a60ff551d1033.mspx?mfr=true

The basic info provided:

To configure TCP/IP for static addressing
1.
Open Network Connections.
2.
Right-click the network connection you want to configure, and then click Properties.
3.
On the General tab (for a local area connection) or the Networking tab (for all other connections), click Internet Protocol (TCP/IP), and then click Properties.
4.
Click Use the following IP address, and do one of the following:
•
For a local area connection, in IP address, Subnet mask, and Default gateway, type the IP address, subnet mask, and default gateway addresses.
•
For all other connections, in IP address, type the IP address.
5.
Click Use the following DNS server addresses.
6.
In Preferred DNS server and Alternate DNS server, type the primary and secondary DNS server addresses.








6) Draw out what the outcome of an Inner Join, Left Outer Join and Right Outer Join would be on two tables.

Can't draw

7) How would you access the database connection strings from a web.config file in VS 2005? (Don't care about VS 2003 anymore :P )

This question really sucks, I wish it was more specific.

If I just need to look it up, I would just open the web.config file and look in the appSetting tag:

<appSettings>
<add key="sqlConn" value="Server=myPc;Database=Northwind" />
<add key="smtpServer" value="smtp.mydomain.com" />
</appSettings>

If I need to access it in the program:

this.sqlConnection1.ConnectionString = ((string)( System.Configuration.ConfigurationSettings.AppSettings.GetValues("sqlConn.ConnectionString"))));


8) Where would you setup “Impersonation” and when would it be a good time to use it?

Source: http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/4ec9116c-7ca2-4126-9dc4-b7f82b67cd76.mspx?mfr=true

"When using impersonation, ASP.NET applications can optionally execute with the identity of the client on whose behalf they are operating. The usual reason for doing this is to avoid dealing with authentication and authorization issues in the ASP.NET application code. Instead, you rely on Internet Information Services (IIS) to authenticate the user and either pass an authenticated token to the ASP.NET application or, if unable to authenticate the user, pass an unauthenticated token. "

In the web.config:

<identity impersonate="true"/>

http://west-wind.com/weblog/posts/1572.aspx goes in nice detail on how to access information that is not allowed with the standard asp.net permissions.

BizTalk Assessment Question: What are the two BAM web services?

What two categories can you find in Business Activity Monitoring (BAM) Web services in Microsoft(R) BizTalk(R) Server 2006? (Each correct answer presents part of the
solution. Choose two.)

1. Human Workflow Services (HWS) service
2. BAM portal BizTalk artifacts
3. BAM query service
4. BAM management service

Answer: BAM query service and BAM management service

1. BAM Query Service – The service is used
by the BAM Portal to retrieve BAM instance data. The service supports the
infrastructure and is not intended to be used directly from your code. The
service is not supported and is not documented. To retrieve instance, use the
supported techniques described at http://msdn.microsoft.com/library/en-us/BTS06BizProcessMgmnt/html/ae4a8854-d5c2-4b36-a0ef-3f74e138306e.asp?frame=true.
2. BamManagementService – The following service provides, consumers the ability to manage subscriptions and alerts among other management operations