C #, ASP. NET, database interview question 2 (with answers), Asp.net interview question C # interview question database...

Body of content: 31. The company requires the development of a component that inherits the system. Windows. Forms. listview class and requires the following special features: Click
When listview columns are headers, all rows in the view can be rearranged according to the values of each row in the clicked column (the sorting method is similar to that in the DataGrid ). Based on your knowledge, please briefly discuss your ideas
A: Based on the column header that you click, the ID of this column is taken out, sorted by this ID, and bound to listview.

32. Specify the following XML file to complete the algorithm flow chart.
<Filesystem>
<Driverc>
<Dir dirname = "msdos622">
<File filename = "command.com"> </File>
</Dir>
<File filename = "msdos. sys"> </File>
<File filename = "Io. sys"> </File>
</Driverc>
</Filesystem>
Draw a flowchart that traverses all file names (filename) (use recursive algorithms ).
A:
Void findfile (Directory D)
{
Fileorfolders = D. getfileorfolders ();
Foreach (fileorfolder fof in fileorfolders)
{
If (FoF is file)
You found a file;
Else if (FoF is directory)
Findfile (FoF );
}
}

33. Write an SQL statement: extract the 31st to 40th records in Table A (sqlserver, with an automatically increasing ID as the primary key, note: the ID may not be continuous.
Answer: solution 1: Select top 10 * from a where id not in (select top 30 ID from)
Solution 2: Select top 10 * from a where ID> (select max (ID) from (select top 30 ID from a) as)

34. object-oriented languages include ________, _________, and ________.
A: encapsulation, inheritance, and polymorphism.

35. To use foreach to traverse the accessed object, you need to implement the ____________ interface or the type of the declared ________________ method.
A: ienumerable and getenumerator.

36. What is GC? Why does GC exist?
A: GC is a garbage collector. Programmers do not have to worry about memory management, because the Garbage Collector will automatically manage. To request garbage collection, you can call one of the following methods:
System. GC ()
Runtime. getruntime (). GC ()

37. String S = new string ("XYZ"); how many string objects are created?
A: There are two objects, one being "xyx" and the other being the reference object s pointing to "xyx.

38. What is the difference between abstract class and interface?
A:
Voice
The class that does not implement the explicit method is called abstract class. It is used to create a class that reflects certain basic behaviors and declare a method for this class, but cannot be in this class
This class is implemented. You cannot create an abstract instance. However, you can create a variable whose type is an abstract class and point it to an instance of a specific subclass. Abstract constructor or
Abstract static methods. The subclasses of abstract classes provide implementation for all abstract methods in their parent classes. Otherwise, they are also abstract classes. Instead, implement this method in the subclass. Others that know their behavior
Class can implement these methods in the class.
An interface is a variant of an abstract class. All methods in the interface are abstract. Multi-inheritance can be achieved by implementing such an interface. Connect
All the methods in the interface are abstract, and none of them have a program body. The interface can only define static final member variables. The implementation of an interface is similar to that of a subclass. Except for this implementation class, you cannot define a relay from the interface.
Behavior. When a class implements a special interface, it defines (to be given by the program body) all the methods of this interface. Then, it can call the interface method on any object that implements the interface class. Because there are abstract classes,
It allows the interface name as the type of the referenced variable. Normally, dynamic Association editing will take effect. The reference can be converted to the interface type or from the interface type. The instanceof operator can be used to determine an object.
Whether the class implements the interface.

39. Do I use run () or start () to start a thread ()?
A: To start a thread is to call the START () method so that the virtual processor represented by the thread is runable, which means it can be scheduled and executed by JVM. This does not mean that the thread will run immediately. The run () method can generate the exit sign to stop a thread.

40. Can an interface inherit the interface? Can an abstract class implement the (implements) interface? Can an abstract class inherit a concrete class )?
A: The interface can inherit the interface. Abstract classes can be implemented (implements) interfaces, and whether abstract classes can inherit object classes, provided that object classes must have clear constructors.

41. Can constructor be overwritten?
A: constructor cannot be inherited, so overriding cannot be overwritten, but overloading can be overloaded.

42. Can I inherit the string class?
A: The string class is a final class, so it cannot be inherited.

43. If there is a return statement in try {}, will the code in finally {} following this try be executed? When will it be executed, before or after return?
A: Yes. It will be executed before return.

44. The two objects have the same value (X. Equals (y) = true), but different hash codes are available, right?
A: No. It has the same hash code.

45. Does swtich work on byte, long, and string?
A: In switch (expr1), expr1 is an integer expression. Therefore, the parameters passed to the switch and case statements should be int, short, Char, or byte. Long and string cannot apply to swtich.

47. After a thread enters a synchronized method of an object, can other threads access other methods of this object?
No. One Synchronized Method of an object can only be accessed by one thread.

48. can abstract methods be both static, native, and synchronized?
A: No.

49. Does list, set, and map inherit from the collection interface?
A: List, set is map, not

50. The elements in the set cannot be repeated. How can we identify whether the elements are repeated or not? Is = or equals () used ()? What are their differences?
A: The elements in the set cannot be repeated. Use the iterator () method to identify whether the elements are repeated or not. Equals () is used to determine whether two sets are equal.
The equals () and = Methods Determine whether the reference value points to the same object equals () is overwritten in the class, in order to return the true value when the content and type of the two separated objects match.

51. Does the array have the length () method? Does string have the length () method?
A: The array does not have the length () method. It has the Length attribute. String has the length () method.

52. What is the difference between sleep () and wait?
A: The sleep () method is used to stop a thread for a period of time. After the sleep interval expires, the thread may not resume execution immediately. This is because at that time, other threads may be running and not scheduled to give up execution, unless (a) the thread "wakes up" has a higher priority.
(B) The Running thread is blocked for other reasons.
When wait () is a thread interaction, if the thread sends a wait () call to a synchronization object X, the thread will pause the execution and the called object will enter the waiting state, wait until the wake-up or wait time is reached.

53. Short S1 = 1; S1 = S1 + 1; what is the error? Short S1 = 1; S1 + = 1; what is the error?
Answer: There is a mistake in short S1 = 1; S1 = S1 + 1; S1 is short type, S1 + 1 is int type, and cannot be explicitly converted to short type. It can be changed to S1 = (short) (S1 + 1 ). Short S1 = 1; S1 + = 1 is correct.

54. Let's talk about the differences between final, finally and finalize.
A:
Final
-Modifier (keyword) If a class is declared as final, it means that it cannot generate a new subclass and cannot be inherited as a parent class. Therefore, a class cannot be declared
Is abstract and declared as final. Declare variables or methods as final to ensure that they are not changed during use. The variable declared as final is required.
The initial value must be given at the time of declaration, but can only be read in future references and cannot be modified. Methods declared as final can only be used and cannot be reloaded.
Finally-The Finally block is provided for troubleshooting. If an exception is thrown, the matched catch clause is executed, and the control enters the Finally block (if any ).
Finalize
-Method name. Java technology allows you to use the finalize () method to clear objects from the memory before the Garbage Collector clears them. This method is garbage collection.
The collector calls this object when it determines that the object is not referenced. It is defined in the object class, so all classes inherit it. Subclass override
Use the finalize () method to sort system resources or perform other cleanup tasks. The finalize () method is called before the Garbage Collector deletes an object.
.

55. How to handle hundreds of thousands of concurrent data records?
A: use stored procedures or transactions. When getting the maximum ID, update it at the same time. Note that the primary key does not have duplicate primary keys when it is not in auto increment mode. A stored procedure is required to obtain the maximum ID.

56. What are the major bugs in session? What methods does Microsoft propose to solve them?
A: The session is lost when the system is busy due to the process recycle mechanism in IIS. You can use sate server or SQL Server database to store the session. However, this method is slow, the end event of the session cannot be captured.

57. What is the difference between a process and a thread?
A: A process is the unit of resource allocation and scheduling by the system. A thread is the unit of CPU scheduling and scheduling. A process can have multiple threads which share the resources of the process.

58. What is the difference between stack and stack?
A:
STACK: the stack is automatically allocated and released by the compiler. Variables defined in the function body are usually on the stack.
Heap: usually assigned and released by programmers. The memory allocated by using new and malloc functions is on the heap.

59. What is the role of adding static before member variables and member functions?
A: They are called common member variables and common member functions, also known as class member variables and class member functions. They are used to reflect the status of the class respectively. For example, a class member variable can be used to count the number of class instances. class member functions are responsible for such statistical actions.

60. asp. Net compared with ASP, what are the main advances?
A: ASP interpretation form and aspx compilation form help improve the performance and protect the source code.

61. generate an int array with a length of 100 and insert 1-100 randomly into it, which cannot be repeated.
Int [] intarr = new int [100];
Arraylist mylist = new arraylist ();
Random RND = new random ();
While (mylist. Count <100)
{
Int num = RND. Next (1,101 );
If (! Mylist. Contains (Num ))
Mylist. Add (Num );
}
For (INT I = 0; I <100; I ++)
Intarr [I] = (INT) mylist [I];
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