There are Four type of symmetric encryption algorithms in .net.

DES 

The Data Encryption Standard (DES) was developed by an IBM team around 1974 and adopted as a national standard in 1977. DES encrypts and decrypts data in 64-bit blocks, using a 64-bit key. Although the input key for DES is 64 bits long, the actual key used by DES is only 56 bits in length. The least significant (right-most) bit in each byte is a parity bit, and should be set so that there are always an odd number of 1s in every byte. These parity bits are ignored, so only the seven most significant bits of each byte are used, resulting in a key length of 56 bits. 

Triple DES 

Triple DES is three times slower than regular DES but can be billions of times more secure if used properly. Triple DES is simply another mode of DES operation. It takes three 64-bit keys, for an overall key length of 192 bits. The procedure for encryption is exactly the same as regular DES, but it is repeated three times, hence the name Triple DES. The data is encrypted with the first key, encrypted with the second key, and finally encrypted again with the third key. Triple DES enjoys much wider use than DES because DES is so easy to break with today's rapidly advancing technology. 

RC2

RC2 (Rivest Cipher) was designed by Ron Rivest as a replacement for DES and boasts a 3 times speed increase over DES. The input and output block sizes are 64 bits each. The key size is variable, from one byte up to 128 bytes, although the current implementation uses eight bytes. The algorithm is designed to be easy to implement on 16-bit microprocessors.

Rijndael

The National Institute of Standards and Technology (NIST) officially announced that Rijndael, designed by Joan Daemen and Vincent Rijmen, would be the new Advanced Encryption Standard.

The Advanced Encryption Standard (AES) is the current encryption standard, intended to be used by  the U.S. Government organisations to protect sensitive (and even secret and top secret) information. It is also becoming a global standard for commercial software and hardware that use encryption. It is a block cipher which uses 128-bit, 192-bit or 256-bit keys. Rijndael is very secure and has no known weaknesses.

Everyone who writes code

Describe the difference between a Thread and a Process?
What is a Windows Service and how does its lifecycle differ from a "standard" EXE?
What is the maximum amount of memory any single process on Windows can address? Is this different than the maximum virtual memory for the system? How would this affect a system design?
What is the difference between an EXE and a DLL?
What is strong-typing versus weak-typing? Which is preferred? Why?
Corillian's product is a "Component Container." Name at least 3 component containers that ship now with the Windows Server Family.
What is a PID? How is it useful when troubleshooting a system?
How many processes can listen on a single TCP/IP port?
What is the GAC? What problem does it solve?
Mid-Level .NET Developer

Describe the difference between Interface-oriented, Object-oriented and Aspect-oriented programming.
Describe what an Interface is and how it’s different from a Class.
What is Reflection?
What is the difference between XML Web Services using ASMX and .NET Remoting using SOAP?
Are the type system represented by XmlSchema and the CLS isomorphic?
Conceptually, what is the difference between early-binding and late-binding?
Is using Assembly.Load a static reference or dynamic reference?
When would using Assembly.LoadFrom or Assembly.LoadFile be appropriate?
What is an Asssembly Qualified Name? Is it a filename? How is it different?
Is this valid? Assembly.Load("foo.dll");
How is a strongly-named assembly different from one that isn’t strongly-named?
Can DateTimes be null?
What is the JIT? What is NGEN? What are limitations and benefits of each?
How does the generational garbage collector in the .NET CLR manage object lifetime? What is non-deterministic finalization?
What is the difference between Finalize() and Dispose()?
How is the using() pattern useful? What is IDisposable? How does it support deterministic finalization?
What does this useful command line do? tasklist /m "mscor*"
What is the difference between in-proc and out-of-proc?
What technology enables out-of-proc communication in .NET?
When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?
Senior Developers/Architects

What’s wrong with a line like this? DateTime.Parse(myString);
What are PDBs? Where must they be located for debugging to work?
What is cyclomatic complexity and why is it important?
Write a standard lock() plus “double check” to create a critical section around a variable access.
What is FullTrust? Do GAC’ed assemblies have FullTrust?
What benefit does your code receive if you decorate it with attributes demanding specific Security permissions?
What does this do? gacutil /l | find /i "Corillian"
What does this do? sn -t foo.dll
What ports must be open for DCOM over a firewall? What is the purpose of Port 135?
Contrast OOP and SOA. What are tenets of each?
How does the XmlSerializer work? What ACL permissions does a process using it require?
Why is catch(Exception) almost always a bad idea?
What is the difference between Debug.Write and Trace.Write? When should each be used?
What is the difference between a Debug and Release build? Is there a significant speed difference? Why or why not?
Does JITting occur per-assembly or per-method? How does this affect the working set?
Contrast the use of an abstract base class against an interface?
What is the difference between a.Equals(b) and a == b?
In the context of a comparison, what is object identity versus object equivalence?
How would one do a deep copy in .NET?
Explain current thinking around IClonable.
What is boxing?
Is string a value type or a reference type?
What is the significance of the "PropertySpecified" pattern used by the XmlSerializer? What problem does it attempt to solve?
Why are out parameters a bad idea in .NET? Are they?
Can attributes be placed on specific parameters to a method? Why is this useful?
C# Component Developers

Juxtapose the use of override with new. What is shadowing?
Explain the use of virtual, sealed, override, and abstract.
Explain the importance and use of each component of this string: Foo.Bar, Version=2.0.205.0, Culture=neutral, PublicKeyToken=593777ae2d274679d
Explain the differences between public, protected, private and internal.
What benefit do you get from using a Primary Interop Assembly (PIA)?
By what mechanism does NUnit know what methods to test?
What is the difference between: catch(Exception e){throw e;} and catch(Exception e){throw;}
What is the difference between typeof(foo) and myFoo.GetType()?
Explain what’s happening in the first constructor: public class c{ public c(string a) : this() {;}; public c() {;} } How is this construct useful?
What is this? Can this be used within a static method?
ASP.NET (UI) Developers

Describe how a browser-based Form POST becomes a Server-Side event like Button1_OnClick.
What is a PostBack?
What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
What is the <machinekey> element and what two ASP.NET technologies is it used for?
What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each?
What is Web Gardening? How would using it affect a design?
Given one ASP.NET application, how many application objects does it have on a single proc box? A dual? A dual with Web Gardening enabled? How would this affect a design?
Are threads reused in ASP.NET between reqeusts? Does every HttpRequest get its own thread? Should you use Thread Local storage with ASP.NET?
Is the [ThreadStatic] attribute useful in ASP.NET? Are there side effects? Good or bad?
Give an example of how using an HttpHandler could simplify an existing design that serves Check Images from an .aspx page.
What kinds of events can an HttpModule subscribe to? What influence can they have on an implementation? What can be done without recompiling the ASP.NET Application?
Describe ways to present an arbitrary endpoint (URL) and route requests to that endpoint to ASP.NET.
Explain how cookies work. Give an example of Cookie abuse.
Explain the importance of HttpRequest.ValidateInput()?
What kind of data is passed via HTTP Headers?
Juxtapose the HTTP verbs GET and POST. What is HEAD?
Name and describe at least a half dozen HTTP Status Codes and what they express to the requesting client.
How does if-not-modified-since work? How can it be programmatically implemented with ASP.NET?
Explain <@OutputCache%> and the usage of VaryByParam, VaryByHeader.
How does VaryByCustom work?
How would one implement ASP.NET HTML output caching, caching outgoing versions of pages generated via all values of q= except where q=5 (as in http://localhost/page.aspx?q=5)?
Developers using XML

What is the purpose of XML Namespaces?
When is the DOM appropriate for use? When is it not? Are there size limitations?
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Write a small XML document that uses a default namespace and a qualified (prefixed) namespace. Include elements from both namespace.
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How would you validate XML using .NET?
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What does it meant to say “the canonical” form of XML?
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