C#, .NET, XML, IIS - Questions

80. What is the managed and unmanaged code in .net?
The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the execution of code and provides services that make the development process easier. Compilers and tools expose the runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that you develop with a language compiler that targets the runtime is called managed code; it benefits from features such as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment support, a simplified model for component interaction, and debugging and profiling services.
81. How do you create threading in .NET? What is the namespace for that?
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System.Threading.Thread
82. Serialize and MarshalByRef?
83. using directive vs using statement
You create an instance in a using statement to ensure that Dispose is called on the object when the using statement is exited. A using statement can be exited either when the end of the using statement is reached or if, for example, an exception is thrown and control leaves the statement block before the end of the statement.
The using directive has two uses:
· Create an alias for a namespace (a using alias).
· Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that namespace (a using directive).
84. Describe the Managed Execution Process?
The managed execution process includes the following steps:
0. Choosing a compiler.
To obtain the benefits provided by the common language runtime, you must use one or more language compilers that target the runtime.
1. Compiling your code to Microsoft intermediate language (MSIL).
Compiling translates your source code into MSIL and generates the required metadata.
2. Compiling MSIL to native code.
At execution time, a just-in-time (JIT) compiler translates the MSIL into native code. During this compilation, code must pass a verification process that examines the MSIL and metadata to find out whether the code can be determined to be type safe.
3. Executing your code.
The common language runtime provides the infrastructure that enables execution to take place as well as a variety of services that can be used during execution.
85. What is Active Directory? What is the namespace used to access the Microsoft Active Directories? What are ADSI Directories?
Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft Windows Active Directory. It enables your applications to interact with diverse directories on a network, using a single interface. Visual Studio .NET and the .NET Framework make it easy to add ADSI functionality with the DirectoryEntry and DirectorySearcher components.
Using ADSI, you can create applications that perform common administrative tasks, such as backing up databases, accessing printers, and administering user accounts. ADSI makes it possible for you to:
· Log on once to work with diverse directories. The DirectoryEntry component class provides username and password properties that can be entered at runtime and communicated to the Active Directory object you are binding to.
· Use a single application programming interface (API) to perform tasks on multiple directory systems by offering the user a variety of protocols to use. The DirectoryServices namespace provides the classes to perform most administrative functions.
· Perform "rich querying" on directory systems. ADSI technology allows for searching for an object by specifying two query dialects: SQL and LDAP.
· Access and use a single, hierarchical structure for administering and maintaining diverse and complicated network configurations by accessing an Active Directory tree.
· Integrate directory information with databases such as SQL Server. The DirectoryEntry path may be used as an ADO.NET connection string provided that it is using the LDAP provider.
using System.DirectoryServices;
86. How Garbage Collector (GC) Works?
The methods in this class influence when an object is garbage collected and when resources allocated by an object are released. Properties in this class provide information about the total amount of memory available in the system and the age category, or generation, of memory allocated to an object. Periodically, the garbage collector performs garbage collection to reclaim memory allocated to objects for which there are no valid references. Garbage collection happens automatically when a request for memory cannot be satisfied using available free memory. Alternatively, an application can force garbage collection using the Collect method.
Garbage collection consists of the following steps:
0. The garbage collector searches for managed objects that are referenced in managed code.
1. The garbage collector attempts to finalize objects that are not referenced.
2. The garbage collector frees objects that are not referenced and reclaims their memory.
87. Why do we need to call CG.SupressFinalize?
Requests that the system not call the finalizer method for the specified object.
public static void SuppressFinalize(
object obj
); The method removes obj from the set of objects that require finalization. The obj parameter is required to be the caller of this method.
Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it.
88. What is nmake tool?
The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based on commands contained in a .mak file.
usage : nmake -a all
89. What are Namespaces?
The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not modifiable.
90. What is the difference between CONST and READONLY?
Both are meant for constant values. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used.
readonly int b;
public X()
{
b=1;
}
public X(string s)
{
b=5;
}
public X(string s, int i)
{
b=i;
}
Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants, as in the following example:
public static readonly uint l1 = (uint) DateTime.Now.Ticks; (this can't be possible with const)
91. What is the difference between ref & out parameters?
An argument passed to a ref parameter must first be initialized. Compare this to an out parameter, whose argument does not have to be explicitly initialized before being passed to an out parameter.
92. What is the difference between Array and LinkedList?
93. What is the difference between Array and Arraylist?
As elements are added to an ArrayList, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize or by setting the Capacity property explicitly.
94. What is Jagged Arrays?
A jagged array is an array whose elements are arrays. The elements of a jagged array can be of different dimensions and sizes. A jagged array is sometimes called an "array-of-arrays."
95. What are indexers?
Indexers are similar to properties, except that the get and set accessors of indexers take parameters, while property accessors do not.
96. What is Asynchronous call and how it can be implemented using delegates?
97. How to create events for a control? What is custom events? How to create it?
98. If you want to write your own dot net language, what steps you will u take care?
99. Describe the difference between inline and code behind - which is best in a loosely coupled solution?
100. how dot net compiled code will become platform independent?
101. without modifying source code if we compile again, will it be generated MSIL again?
102. C++ & C# differences
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(COM)
103. Interop Services?
The common language runtime provides two mechanisms for interoperating with unmanaged code:
· Platform invoke, which enables managed code to call functions exported from an unmanaged library.
· COM interop, which enables managed code to interact with COM objects through interfaces.
Both platform invoke and COM interop use interop marshaling to accurately move method arguments between caller and callee and back, if required.
104. How does u handle this COM components developed in other programming languages in .NET?
105. What is RCW (Runtime Callable Wrappers)?
The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object.
106. What is CCW (COM Callable Wrapper)
A proxy object generated by the common language runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently.
107. How CCW and RCW is working?
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108. How will you register com+ services?
The .NET Framework SDK provides the .NET Framework Services Installation Tool (Regsvcs.exe - a command-line tool) to manually register an assembly containing serviced components. You can also access these registration features programmatically with the System.EnterpriseServicesRegistrationHelper class by creating an instance of class RegistrationHelper and using the method InstallAssembly
109. What is use of ContextUtil class?
ContextUtil is the preferred class to use for obtaining COM+ context information.
110. What is the new three features of COM+ services, which are not there in COM (MTS)?
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111. Is the COM architecture same as .Net architecture? What is the difference between them?
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112. Can we copy a COM dll to GAC folder?
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113. What is Pinvoke?
Platform invoke is a service that enables managed code to call unmanaged functions implemented in dynamic-link libraries (DLLs), such as those in the Win32 API. It locates and invokes an exported function and marshals its arguments (integers, strings, arrays, structures, and so on) across the interoperation boundary as needed.
114. Is it true that COM objects no longer need to be registered on the server?
Answer: Yes and No. Legacy COM objects still need to be registered on the server before they can be used. COM developed using the new .NET Framework will not need to be registered. Developers will be able to auto-register these objects just by placing them in the 'bin' folder of the application.
115. Can .NET Framework components use the features of Component Services?
Answer: Yes, you can use the features and functions of Component Services from a .NET Framework component. http://msdn.microsoft.com/library/techart/Pahlcompserv.htm

(OOPS)
116. What are the OOPS concepts?
1) Encapsulation: It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and misuse. In short it isolates a particular code and data from all other codes and data. A well-defined interface controls the access to that particular code and data.
2) Inheritance: It is the process by which one object acquires the properties of another object. This supports the hierarchical classification. Without the use of hierarchies, each object would need to define all its characteristics explicitly. However, by use of inheritance, an object need only define those qualities that make it unique within its class. It can inherit its general attributes from its parent. A new sub-class inherits all of the attributes of all of its ancestors.
3) Polymorphism: It is a feature that allows one interface to be used for general class of actions. The specific action is determined by the exact nature of the situation. In general polymorphism means "one interface, multiple methods", This means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler's job to select the specific action (that is, method) as it applies to each situation.
117. What is the difference between a Struct and a Class?
· The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive.
· When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized.
· It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.
· It is an error to initialize an instance field in a struct.
· There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.
· A struct is a value type, while a class is a reference type.
118. Value type & reference types difference? Example from .NET. Integer & struct are value types or reference types in .NET?
Most programming languages provide built-in data types, such as integers and floating-point numbers, that are copied when they are passed as arguments (that is, they are passed by value). In the .NET Framework, these are called value types. The runtime supports two kinds of value types:
· Built-in value types
The .NET Framework defines built-in value types, such as System.Int32 and System.Boolean, which correspond and are identical to primitive data types used by programming languages.
· User-defined value types
Your language will provide ways to define your own value types, which derive from System.ValueType. If you want to define a type representing a value that is small, such as a complex number (using two floating-point numbers), you might choose to define it as a value type because you can pass the value type efficiently by value. If the type you are defining would be more efficiently passed by reference, you should define it as a class instead.
Variables of reference types, referred to as objects, store references to the actual data. This following are the reference types:
· class
· interface
· delegate
This following are the built-in reference types:
· object
· string
119. What is Inheritance, Multiple Inheritance, Shared and Repeatable Inheritance?
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120. What is Method overloading?
Method overloading occurs when a class contains two methods with the same name, but different signatures.
121. What is Method Overriding? How to override a function in C#?
Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new implementation of a member inherited from a base class. The method overridden by an override declaration is known as the overridden base method. The overridden base method must have the same signature as the override method.
You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override.
122. Can we call a base class method without creating instance?
Its possible If its a static method.
Its possible by inheriting from that class also.
Its possible from derived classes using base keyword.
123. You have one base class virtual function how will call that function from derived class?
Ans:
124. class a
125. {
126. public virtual int m()
127. {
128. return 1;
129. }
130. }
131. class b:a
132. {
133. public int j()
134. {
135. return m();
136. }
}
137. In which cases you use override and new base?
Use the new modifier to explicitly hide a member inherited from a base class. To hide an inherited member, declare it in the derived class using the same name, and modify it with the new modifier.
C# Language features
138. What are Sealed Classes in C#?
The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified as the base class of another class. (A sealed class cannot also be an abstract class)
139. What is Polymorphism? How does VB.NET/C# achieve polymorphism?
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140. class Token
141. {
142. public string Display()
143. {
144. //Implementation goes here
145. return "base";
146. }
147. }
148. class IdentifierToken:Token
149. {
150. public new string Display() //What is the use of new keyword
151. {
152. //Implementation goes here
153. return "derive";
154. }
155. }
156. static void Method(Token t)
157. {
158. Console.Write(t.Display());
159. }
160. public static void Main()
161. {
162. IdentifierToken Variable=new IdentifierToken();
163. Method(Variable); //Which Class Method is called here
164. Console.ReadLine();
165. }
166. For the above code What is the "new" keyword and Which Class Method is
167. called here
A: it will call base class Display method
168. class Token
169. {
170. public virtual string Display()
171. {
172. //Implementation goes here
173. return "base";
174. }
175. }
176. class IdentifierToken:Token
177. {
178. public override string Display() //What is the use of new keyword
179. {
180. //Implementation goes here
181. return "derive";
182. }
183. }
184. static void Method(Token t)
185. {
186. Console.Write(t.Display());
187. }
188. public static void Main()
189. {
190. IdentifierToken Variable=new IdentifierToken();
191. Method(Variable); //Which Class Method is called here
192. Console.ReadLine();
193. }
194. A: Derive
195. In which Scenario you will go for Interface or Abstract Class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes. Even though class inheritance allows your classes to inherit implementation from a base class, it also forces you to make most of your design decisions when the class is first published.
Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code.
Interfaces vs. Abstract Classes
Feature Interface Abstract class
Multiple inheritance A class may implement several interfaces. A class may extend only one abstract class.
Default implementation An interface cannot provide any code at all, much less default code. An abstract class can provide complete code, default code, and/or just stubs that have to be overridden.
Constants Static final constants only, can use them without qualification in classes that implement the interface. On the other paw, these unqualified names pollute the namespace. You can use them and it is not obvious where they are coming from since the qualification is optional. Both instance and static constants are possible. Both static and instance intialiser code are also possible to compute the constants.
Third party convenience An interface implementation may be added to any existing third party class. A third party class must be rewritten to extend only from the abstract class.
is-a vs -able or can-do Interfaces are often used to describe the peripheral abilities of a class, not its central identity, e.g. an Automobile class might implement the Recyclable interface, which could apply to many otherwise totally unrelated objects. An abstract class defines the core identity of its descendants. If you defined a Dog abstract class then Damamation descendants are Dogs, they are not merely dogable. Implemented interfaces enumerate the general things a class can do, not the things a class is.
Plug-in You can write a new replacement module for an interface that contains not one stick of code in common with the existing implementations. When you implement the interface, you start from scratch without any default implementation. You have to obtain your tools from other classes; nothing comes with the interface other than a few constants. This gives you freedom to implement a radically different internal design. You must use the abstract class as-is for the code base, with all its attendant baggage, good or bad. The abstract class author has imposed structure on you. Depending on the cleverness of the author of the abstract class, this may be good or bad. Another issue that's important is what I call "heterogeneous vs. homogeneous." If implementors/subclasses are homogeneous, tend towards an abstract base class. If they are heterogeneous, use an interface. (Now all I have to do is come up with a good definition of hetero/homogeneous in this context.) If the various objects are all of-a-kind, and share a common state and behavior, then tend towards a common base class. If all they share is a set of method signatures, then tend towards an interface.
Homogeneity If all the various implementations share is the method signatures, then an interface works best. If the various implementations are all of a kind and share a common status and behavior, usually an abstract class works best.
Maintenance If your client code talks only in terms of an interface, you can easily change the concrete implementation behind it, using a factory method. Just like an interface, if your client code talks only in terms of an abstract class, you can easily change the concrete implementation behind it, using a factory method.
Speed Slow, requires extra indirection to find the corresponding method in the actual class. Modern JVMs are discovering ways to reduce this speed penalty. Fast
Terseness The constant declarations in an interface are all presumed public static final, so you may leave that part out. You can't call any methods to compute the initial values of your constants. You need not declare individual methods of an interface abstract. They are all presumed so. You can put shared code into an abstract class, where you cannot into an interface. If interfaces want to share code, you will have to write other bubblegum to arrange that. You may use methods to compute the initial values of your constants and variables, both instance and static. You must declare all the individual methods of an abstract class abstract.
Adding functionality If you add a new method to an interface, you must track down all implementations of that interface in the universe and provide them with a concrete implementation of that method. If you add a new method to an abstract class, you have the option of providing a default implementation of it. Then all existing code will continue to work without change.