C# interview questions
1 Describe the difference between a Thread and a Process?
2 What is a Windows Service and how does its lifecycle differ from a "standard" EXE?
3 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?
4 What is the difference between an EXE and a DLL?
5 What is strong-typing versus weak-typing? Which is preferred? Why?
6 Corillian's product is a "Component Container." Name at least 3 component containers that ship now with the Windows Server Family.
7 What is a PID? How is it useful when troubleshooting a system?
8 How many processes can listen on a single TCP/IP port?
9 What is the GAC? What problem does it solve?
10 What is serialization in .NET? What are the ways to control serialization?
11 Does C# support multiple inheritance?
12 What’s the implicit name of the parameter that gets passed into the class’ set method?
13 What’s the top .NET class that everything is derived from?
14 How’s method overriding different from overloading?
15 What is CLR?
16 What is CTS?
17 What is CLS?
18 What is strong name?
19 What is Application Domain?
20 Describe the difference between Interface-oriented, Object-oriented and Aspect-oriented programming.
Are C# destructors the same as C++ destructors?
No. They look the same but they are very different. The C# destructor syntax (with the familiar ~ character) is just syntactic sugar for an override of the System.Object Finalize method. This Finalize method is called by the garbage collector when it determines that an object is no longer referenced, before it frees the memory associated with the object. So far this sounds like a C++ destructor. The difference is that the garbage collector makes no guarantees about when this procedure happens. Indeed, the algorithm employed by the CLR garbage collector means that it may be a long time after the application has finished with the object. This lack of certainty is often termed ‘non-deterministic finalization’, and it means that C# destructors are not suitable for releasing scarce resources such as database connections, file handles etc.To achieve deterministic destruction, a class must offer a method to be used for the purpose. The standard approach is for the class to implement the IDisposable interface. The user of the object must call the Dispose() method when it has finished with the object. C# offers the ‘using’ construct to make this easier.
What is viewstate in ASP.NET?
The postback question is the heart of any interview on ASP NET. When a postback happens (i.e. when a form is submitted to a server), the variable values that are set in the code-behind page are erased from the memory of the client system. This concept would be different from what happens in Windows-based applications, where the variable variables persist in memory until they are freed from the memory either by the garbage collector, or by specific codes like dispose or finalize.
In web applications, variable values simply get erased. But it is very simple to persist these values. They may be persisted using the Viewstate object. Before the postback is invoked, the variable's value is saved in a viewstate object. In the recieving page, the viewstate's value may be retrieved back. See example code below...
//Save the value in ViewState object before the PostBack
ViewState("SomeVar") = txtFirstName.text;
//Retrieve the value from ViewState object after the PostBack
String strFirstName = ViewState("SomeVar").ToString();
In-process Mode in asp.net
In-process mode simply means using ASP.NET session state in a similar manner to classic ASP session state. That is, session state is managed in process and if the process is re-cycled, state is lost. Given the new settings that ASP.NET provides, you might wonder why you would ever use this mode. The reasoning is quite simple: performance. The performance of session state, e.g. the time it takes to read from and write to the session state dictionary, will be much faster when the memory read to and from is in process, as cross-process calls add overhead when data is marshaled back and forth or possibly read from SQL Server.
In-process mode is the default setting for ASP.NET. When this setting is used, the only other session config.web settings used are cookieless and timeout.
If we call SessionState.aspx, set a session state value, and stop and start the ASP.NET process (iisreset), the value set before the process was cycled will be lost.
What are the main advantages of binary serialization?
An object is stored in a file, a database or even in the memory. However, data to be transferred over a network needs to be in a linear form for which serialization and deserialization are used.
Advantage of serialization is the ability of an object to be serialized into a persistent or a non-persistent storage media and then reconstructing the same object later by de-serializing the object.
Also Binary Serialization is faster, supports complex objects too with read only properties and even circular references.
.NET interview: What are the main advantages of binary serialization
An object is stored in a file, a database or even in the memory. However, data to be transferred over a network needs to be in a linear form for which serialization and deserialization are used.
Advantage of serialization is the ability of an object to be serialized into a persistent or a non-persistent storage media and then reconstructing the same object later by de-serializing the object.
Also Binary Serialization is faster, supports complex objects too with read only properties and even circular references.
Design Pattern – proxy pattern
Proxy fundamentally is a class functioning as in interface which points towards the actual class which has data. This actual data can be a huge image or an object data which very large and can not be duplicated. So you can create multiple proxies and point towards the huge memory consuming object and perform operations. This avoids duplication of the object and thus saving memory. Proxies are references which points towards the actual object.
Figure ‘Proxy and actual object’ shows how we have created an interface which is implemented by the actual class. So the interface ‘IImageProxy’ forms the proxy and the class with implementation i.e. ‘clsActualImage’ class forms the actual object. You can see in the client code how the interface points towards the actual object.
Figure: - Proxy and actual object
The advantages of using proxy are security and avoiding duplicating objects which are of huge sizes. Rather than shipping the code we can ship the proxy, thus avoiding the need of installing the actual code at the client side. With only the proxy at the client end we ensure more security. Second point is when we have huge objects it can be very memory consuming to move to those large objects in a network or some other domain. So rather than moving those large objects we just move the proxy which leads to better performance.
