1. Can you store multiple data types in System.Array? No.
1.What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass
2.Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
3.Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
4.What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5.When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
2. When at least one of the methods in the class is abstract.
6.What is an interface 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.
-by def methods are public
1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
Value. The data type of the value parameter is defined by whatever data type the property is declared .
2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.
3. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.
4. Can you declare an override method to be static if the original method is not static?
No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
5. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
1. What’s a delegate?
A delegate object encapsulates a reference to a method.
2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.
3. What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and it’s datatype depends on whatever variable we’re changing.
4. How do you inherit from a class in C#?
Place a colon and then the name of the base class.
5. Does C# support multiple inheritance?
No, use interfaces instead.
6. When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.
7. Are private class-level variables inherited?
Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited.
8. Describe the accessibility modifier protected internal.?
It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
9. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
10. What’s the top .NET class that everything is derived from?
System.Object.
11. How’s method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
12. What does the keyword virtual mean in the method definition?
The method can be over-ridden.
13. Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
14. Can you override private virtual methods?
No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
15. Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName.
It’s the same concept as final class in Java.
16. Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.
17. What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden.
Essentially, it’s a blueprint for a class without any implementation.
18. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
19. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
20. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
21. Can you inherit multiple interfaces?
Yes, why not.
22. And if they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you.
This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
23. What’s the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
24. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.
25. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
26. What’s the difference between System.String and System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
27. Is it namespace class or class namespace?
The .NET class library is organized into namespaces. Each namespace contains a functionally related group of classes so natural namespace comes first.
static constructor bytfz abl mt3aml m3 el class
2. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
3. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
4. What’s the .NET datatype that allows the retrieval of data by a unique key?HashTable.
6. Will finally block get executed if the exception had not occurred? Yes.
7. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
8. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
9. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
10. What’s a delegate? A delegate object encapsulates a reference to a method(typesafe). In C++ they were referred to as function pointers.
11. What’s a multicast delegate? it is a delegate which holds the reference of more than one method.Multicast delegates must contain only methods that return void, else there is a run-time exception.
12.How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the Assembly.
13.What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
14.What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
15. What namespaces are necessary to create a localized application?System.Globalization, System.Resources.
16.What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
17. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
18.What’s the difference between <c> and <code> XML documentation tag? Single line code example and multiple-line code example.
19.Is XML case-sensitive? Yes, so <Student> and <student> are different elements.
20. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
21.What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
22. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
23. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
24. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
25. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
26. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
27. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
28. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
29. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
30. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
31.What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
32. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
33. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
34. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
35. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
36. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
37. What does the parameter Initial Catalog define inside Connection String?The database name to connect to.
38. What’s the data provider name to connect to Access database? Microsoft.Access.
39. What does Dispose method do with the connection object? Deletes it from the memory.
40. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
//////////////////////////////////////////////////////////////////////////////////////
1.Does C# support multiple-inheritance?
No. But you can use Interfaces.
2.Where is a protected class-level variable available?
It is available to any sub-class derived from base class
3.Are private class-level variables inherited?
Yes, but they are not accessible.
4.Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
6.Which class is at the top of .NET class hierarchy?
System.Object.
7.What does the term immutable mean?
The data value may not be changed.
Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
8.What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable.
System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
9.What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
10.Can you store multiple data types in System.Array?
No.
11.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
12.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
13.What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
14.What class is underneath the SortedList class?
A sorted HashTable.
15.Will the finally block get executed if an exception has not occurred?
Yes.
16.What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
17.Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block .
18.Explain the three services model commonly know as a three-tier application?
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
No. But you can use Interfaces.
2.Where is a protected class-level variable available?
It is available to any sub-class derived from base class
3.Are private class-level variables inherited?
Yes, but they are not accessible.
4.Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
6.Which class is at the top of .NET class hierarchy?
System.Object.
7.What does the term immutable mean?
The data value may not be changed.
Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
8.What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable.
System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
9.What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
10.Can you store multiple data types in System.Array?
No.
11.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
12.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
13.What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
14.What class is underneath the SortedList class?
A sorted HashTable.
15.Will the finally block get executed if an exception has not occurred?
Yes.
16.What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
17.Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block .
18.Explain the three services model commonly know as a three-tier application?
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Class Questions
1.What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass
2.Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
3.Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
4.What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5.When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
2. When at least one of the methods in the class is abstract.
6.What is an interface 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.
-by def methods are public
-no def for methods
-no member data
7.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.
8.Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.
9.What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
7.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.
8.Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.
9.What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
Method and Property Questions
1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
Value. The data type of the value parameter is defined by whatever data type the property is declared .
2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.
3. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.
4. Can you declare an override method to be static if the original method is not static?
No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
5. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
Events and Delegates
1. What’s a delegate?
A delegate object encapsulates a reference to a method.
2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.
3. What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and it’s datatype depends on whatever variable we’re changing.
4. How do you inherit from a class in C#?
Place a colon and then the name of the base class.
5. Does C# support multiple inheritance?
No, use interfaces instead.
6. When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.
7. Are private class-level variables inherited?
Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited.
8. Describe the accessibility modifier protected internal.?
It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
9. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
10. What’s the top .NET class that everything is derived from?
System.Object.
11. How’s method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
12. What does the keyword virtual mean in the method definition?
The method can be over-ridden.
13. Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
14. Can you override private virtual methods?
No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
15. Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName.
It’s the same concept as final class in Java.
16. Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.
17. What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden.
Essentially, it’s a blueprint for a class without any implementation.
18. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
19. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
20. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
21. Can you inherit multiple interfaces?
Yes, why not.
22. And if they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you.
This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
23. What’s the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
24. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.
25. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
26. What’s the difference between System.String and System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
27. Is it namespace class or class namespace?
The .NET class library is organized into namespaces. Each namespace contains a functionally related group of classes so natural namespace comes first.
Difference between class and struct:
Classes are reference types and structs are value types.
Since classes are reference type, a class variable can be assigned null.But we cannot assign null to a struct variable, since structs are value type.
2. When you instantiate a class, it will be allocated on the heap.When you instantiate a struct, it gets created on the stack.
3. You will always be dealing with reference to an object ( instance ) of a class. But you will not be dealing with references to an instance of a struct ( but dealing directly with them ).
4. When passing a class to a method, it is passed by reference. When passing a struct to a method, it’s passed by value instead of as a reference.
5. You cannot have instance Field initializers in structs.But classes can have
example:
class MyClass
{
int myVar =10; // no syntax error.
public void MyFun( )
{
// statements
}
}
struct MyStruct
{
int myVar = 10; // syntax error.
public void MyFun( )
{
// statements
}
}
6. Classes can have explicit parameterless constructors. But structs cannot have
7. Classes must be instantiated using the new operator. But structs can be
8. Classes support inheritance.But there is no inheritance for structs.
( structs don’t support inheritance polymorphism )
9. Since struct does not support inheritance, access modifier of a member of a struct cannot be protected or protected internal.11. A class is permitted to declare a destructor.But a struct is not
12. classes are used for complex and large set data. structs are simple to use.
Since classes are reference type, a class variable can be assigned null.But we cannot assign null to a struct variable, since structs are value type.
2. When you instantiate a class, it will be allocated on the heap.When you instantiate a struct, it gets created on the stack.
3. You will always be dealing with reference to an object ( instance ) of a class. But you will not be dealing with references to an instance of a struct ( but dealing directly with them ).
4. When passing a class to a method, it is passed by reference. When passing a struct to a method, it’s passed by value instead of as a reference.
5. You cannot have instance Field initializers in structs.But classes can have
example:
class MyClass
{
int myVar =10; // no syntax error.
public void MyFun( )
{
// statements
}
}
struct MyStruct
{
int myVar = 10; // syntax error.
public void MyFun( )
{
// statements
}
}
6. Classes can have explicit parameterless constructors. But structs cannot have
7. Classes must be instantiated using the new operator. But structs can be
8. Classes support inheritance.But there is no inheritance for structs.
( structs don’t support inheritance polymorphism )
9. Since struct does not support inheritance, access modifier of a member of a struct cannot be protected or protected internal.11. A class is permitted to declare a destructor.But a struct is not
12. classes are used for complex and large set data. structs are simple to use.
-Class inherits static members of the parent
.net solve the cross language cross platform problem
-output from c# or VB is IL(intermediate language)
-jit:just in time compiler convert IL to native
What is a IL? What is MSIL or CIL , What is JIT? (IL)Intermediate Language is also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code is compiled to IL. This IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In- Time (JIT) compiler.
What is a CLR? Full form of CLR is Common Language Runtime and it forms the heart of the .NET framework. All Languages have runtime and its the responsibility of the runtime to take care of the code execution of the program. For example VC++ has MSCRT40.DLL,VB6 has MSVBVM60.DLL, Java has Java Virtual Machine etc. Similarly .NET has CLR. Following are the responsibilities of CLR
√ Garbage Collection :- CLR automatically manages memory thus eliminating memory leaks. When objects are not referred GC automatically releases those memories thus providing efficient memory management.
√ Code Access Security :- CAS grants rights to program depending on the security configuration of the machine. Example the program has rights to edit or create a new file but the security configuration of machine does not allow the program to delete a file. CAS will take care that the code runs under the environment of machines security configuration.
√ Code Verification :- This ensures proper code execution and type safety while the code runs. It prevents the source code to perform illegal operation such as accessing invalid memory locations etc.
√ IL( Intermediate language )-to-native translators and optimizer’s :- CLR uses JIT and compiles the IL code to machine code and then executes. CLR also determines depending on platform what is optimized way of running the IL code.
What is a CTS? In order that two language communicate smoothly CLR has CTS (Common Type System).Example in VB you have “Integer” and in C++ you have “long” these datatypes are not compatible so the interfacing between them is very complicated. In order to able that two different languages can communicate Microsoft introduced Common Type System. So “Integer” datatype in VB6 and “int” datatype in C++ will convert it to System.int32 which is datatype of CTS. CLS which is covered in the coming question is subset of CTS.
What is a CLS(Common Language Specification)? This is a subset of the CTS which all .NET languages are expected to support. It was always a dream of Microsoft to unite all different languages in to one umbrella and CLS is one step towards that. Microsoft has defined CLS which are nothing but guidelines that language to follow so that it can communicate with other .NET languages in a seamless manner.
What is a Managed Code? Managed code runs inside the environment of CLR i.e. .NET runtime. In short all IL are managed code. But if you are using some third party software example VB6 or VC++ component they are unmanaged code as .NET runtime (CLR) does not have control over the source code execution of the language
What is a Assembly?
√ Assembly is unit of deployment like EXE or a DLL.
√ An assembly consists of one or more files (dlls, exe’s, html files etc.), and represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing.
√ An assembly is completely self-describing.An assembly contains metadata information, which is used by the CLR for everything from type checking and security to actually invoking the components methods. As all information is in the assembly itself, it is independent of registry. This is the basic advantage as compared to COM where the version was stored in registry.
√ Multiple versions can be deployed side by side in different folders. These different versions can execute at the same time without interfering with each other. Assemblies can be private or shared. For private assembly deployment, the assembly is copied to the same directory as the client program that references it. No registration is needed, and no fancy installation program is required.When the component is removed, no registry cleanup is needed, and no uninstall program is required. Just delete it from the hard drive.
√ In shared assembly deployment, an assembly is installed in the Global Assembly Cache (or GAC). The GAC contains shared assemblies that are globally accessible to all .NET applications on the machine.
An assembly is composed of four sections. The first is the assembly manifest. The manifest
contains information about the assembly, itself. This data includes such things as the name of the assembly, its version number, type mapping information, and cultural settings.
The second section is type metadata, which is information about the data types used by the program.Among other benefits, type metadata aids in cross-language interoperability. The third part of an assembly is the program code, which is stored in Microsoft Intermediate Language (MSIL) format. The fourth constituent of an assembly is the resources used by the program. Fortunately, when using C#, assemblies are produced automatically, with little or no extra effort on your part. The reason for this is that the exe file created when you compile a C# program is actually an assembly that contains your program’s executable code as well as other types of information. Thus, when you compile a C# program, an assembly is automatically produced.
What are the different types of Assembly?
There are two types of assembly Private and Public assembly. A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. Crystal report classes which will be used by all application for Reports.
What is NameSpace? Namespace has two basic functionality :-
√ NameSpace Logically group types, example System.Web.UI logically groups our UI related features.
√ In Object Oriented world many times its possible that programmers will use the same class name.By qualifying NameSpace with classname this collision can be avoided.
What is Difference between NameSpace and Assembly? Following are the differences between namespace and assembly : √ Assembly is physical grouping of logical units. Namespace logically groups classes. √ Namespace can span multiple assembly.
If you want to view a Assembly how do you go about it ? Twist : What is ILDASM ? When it comes to understanding of internals nothing can beat ILDASM. ILDASM basically converts the whole exe or dll in to IL code. To run ILDASM you have to go to "C:\Program Files\Microsoft71 Visual Studio .NET 2003\SDK\v1.1\Bin". Note that i had v1.1 you have to probably change it depending on the type of framework version you have. If you run IDASM.EXE from the path you will be popped with the IDASM exe program as shown in figure ILDASM. Click on file and browse to the respective directory for the DLL whose assembly you want to view. After you select the DLL you will be popped with a tree view details of the DLL as shown in figure ILDASM. On double clicking on manifest you will be able to view details of assembly, internal IL code .
What is Manifest? Assembly metadata is stored in Manifest. Manifest contains all the metadata needed to do the following things (See Figure Manifest View for more details):
√ Version of assembly
√ Security identity
√ Scope of the assembly
√ Resolve references to resources and classes.
√ The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a stand-alone PE file that contains only assembly manifest information.
What is GAC ? Twist :- What are situations when you register .NET assembly in GAC ? GAC (Global Assembly Cache) is used where shared .NET assembly reside. GAC is used in the following situations :-
√ If the application has to be shared among several application.
√ If the assembly has some special security requirements like only administrators can remove the assembly. If the assembly is private then a simple delete of assembly the assembly file will remove the assembly. Note :- Registering .NET assembly in GAC can lead to the old problem of DLL hell, where COM version was stored in central registry. So GAC should be used when absolutely necessary.
Cannot access uninitialized value type variable
Decimal used when we don’t want approximation
Stack uninitialized & heap initialized
Attributes: specify additional information. The information that attributes contain can be retrieved at run time through reflection. You can use predefined attributes or you can define your own custom attributes
Reflection: The classes in the Reflection namespace, together with System.Type, allow you to obtain information about loaded assemblies and the types defined within them, such as classes,interfaces, and value types. You can also use reflection to create type instances at run time, and to invoke and access them.
Casting:
(value , value)
safe casting: long=int (implicit)
unsafe (narrow) casting:int=long
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lw ref w value yb2a boxing w unboxing
no global variables in C#
Switch case:
Int and string only
Lw float ht3ml cast to int
Break not optional
Static function deal only with static members
Boxing:value type in refrance tyb
Unboxing: refrance tyb in value tyb
Int x;cannot take null value
Int? x:take null value
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Stack trace used to know information about the function
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Diffrance between ref and out
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Out:msh lazm n3ml initialize
Value by value
Value by ref
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Ref by ref:like pointer to pointer keda bshawr ala refrance ele fe stack
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Finally : b7t feha code hytfz 7ta lw 7sl upnormal termination
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Interface:abstract class kl ele gwah abstract methods
Struct lw h3ml constructor yb2a lazm a3ml initialization lkl el fields
Struct:no destructor
No abstract
No virtual methods
No inhertance
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Indexer to make object act as an array
We can overload indexer but we cannot overload property
Internal access modifier:can be accessed in the assembly only
Internal protected :can be accessed in the assembly or in any child thet inherit the class
To return object with the same name and different identity implement the Icolonable interface and override the colone func
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static constructor bytfz abl mt3aml m3 el class
sealed class : class cannot be inhirted
sealed func cannot be overridden
==,equal in value we can override them for performance
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{
==,equals in ref type: by default compare by identity
Its preferred to override the .equals and make it compare by value and if your object will be used as a key in ex. hashtable you must override gethashcode fuction
Reason is as follows:
There is a general rule that two objects considered equal should return the same hash code. Now , you have overrioden equals but not gethashcode. GetHashCode() in System.Object is not guaranteed to return consistent or unique values. SO by not overridng GetHashCode(), you have inherited this flawed implementation from System.Object
So by overriding equals but not GetHashCode(), you are violating (ok not so much violating as ignoring) the cardinal rule, that your equals method will return that tow objects are equal but the GetHashCode() method may not return the same hash codes for both the objects.
}
Arraylist not type safe has indexer can be used to retrieve or update data
1. Constrain on generic class :
2. Primary:struct,class,specific class
3. Secoundry:multible constrains (interface)
4. Construtor 1:new() lazm ele yege ykon 3ndo constructor msh bya5d input
Invoke list of delegate has method and target
Target will be null for static method or it will point to the object if method isnot static
Built in delegate:
1. Action<T>: return void and take upto 16 argument
2. Func: public delegate TResult Func<out TResult>()
3. Predicate: public delegate bool Predicate<in T>(T obj)
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