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.

Interview question: What structure would you use to represent shapes in a database?

OK, A few months ago, my friend told me of an interview question that I found interesting. The question that was given to him, paraphrasing: "If you had to set up a database to hold shapes, what would your table structure look like?". The point of the question was for him to convert the concept of a class shape that might be used in an object oriented language to be converted to a database structure. Which is why I was stuck on this question, with no simple straight forward solution.

I then started thinking about this question, again. The idea of the question was to see what tables and columns would you set up to make this feasible. I wanted an easy solution with minimal work, so I avoided the polymorphism concept and went to a simpler definition of a shape (polygon).

I figure I would make 1 table called SHAPE with 2 columns and make the assumption that the shapes are defined as "simple polygons":


ID int, COORDINATES varchar





The ID is obviously the primary key for each shape.


The Coordinates is a order list of Cartesian coordinates going counter-clockwise.

Now, given a shape, the most common questions asked would be what is the perimeter and area of said shape. I could easily make 2 store procedures to find the perimeter and area.

To figure out the perimeter, I just need to add up the distance from each point, simple enough.

To figure out the area of the polygon, I knew there had to be a formula that would do this for me, and thanks to wikipedia I found one:





"The formula was described by Meister in 1769 and by Gauss in 1795. It can be verified by dividing the polygon into triangles".


I was looking around, to see if others seen this question. I did find something similar at http://lists.mysql.com/mysql/207823

If I needed to query the table for certain shapes, then it would be good to add an additional column called: Points int

So, if I needed to query the table for triangles only then I can do a search on points = 3.

SQL Interview Questions: Definitions

Questions:
1) What is a SARGABLE predicate?
2) What is DAS? What is NAS? What is a SAN? Name the two main types of SAN networks. What is the common name for the device used to interface to a SAN?
3) What is a LUN? How is it used with a SAN?
4) What is a RAID? What RAID format is the recommended best practice for SQL Server, and why?
5) What is an INSTEAD-OF trigger used for?
6) What is a LOB?





Answers?:
1) Predicates that do searching, like Year > 2000.
2) Direct Attached Storage, Network Attached Storage, Storage Area Network, Fibre Channel and iSCSI, Host Bus Adapter.
3) Logical Unit Number , Each device(or LUN) on the storage area network (SAN) is "owned" by a single computer (or initiator)
4) RAID (Redundant Array of Independent Disks). A collection of disk drives that offers increased performance and fault tolerance. There are a number of different RAID levels. The three most commonly used are 0, 1, and 5. Microsoft recommends a RAID that would provide the best write performance. For each write request a RAID0 would write once, RAID1 or RAID10 would write twice, and RAID5 would write 4 times. RAID 0 is never recommended, so this leaves RAID10 as the recommended.

Here are the RAIDs:
Level 0: striping without parity (spreading out blocks of each file across multiple disks).
Level 1: disk mirroring or duplexing.
Level 2: bit-level striping with parity
Level 3: byte-level striping with dedicated parity. Same as Level 0, but also reserves one dedicated disk for error correction data. It provides good performance and some level of fault tolerance.
Level 4: block-level striping with dedicated parity
Level 5: block-level striping with distributed parity
Level 6: block-level striping with two sets of distributed parity for extra fault tolerance
Level 7: Asynchronous, cached striping with dedicated parity

5) There are 3 types of triggers: BEFORE, AFTER and INSTEAD OF. BEFORE is used to affect the row before the trigger event executes. AFTER is used to trigger actions are activiated for the affected rows. INSTEAD OF is used to triggers its action for each row in the affected row instead of using the trigger event.

6) Locator OBject.