Question And Answer.

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1 Q.1 Which type of of the following code will throw? Using System; Using system.io; Class program Static void Main() Try //Read in non-existent file. Using (StreamReader reader = new StreamReader(^aEURoeI-Am ^aeur"not-present.txt^aeur Q.2 Which of the following statements are correct about exception handling in C#.NET? I. try blocks cannot be nested. II. In one function, there can be only one try block. III. An exception must be caught in the same function in which it is thrown. IV. All values set up in the exception object are available in the catch block. V. While throwing a user-defined exception multiple values can be set in the exception, object. A. I only B. I and II only C. III only D. IV and V only ANSWER : Option B I and II only option 1st isincorrecttryblockcan not be nested because try may nested Option 2nd is incorrect because in one functions there can be more than one try block as we already discuss try may nested Option 4th and 5th is correct because for every try there must be have a catch block Q.3 Can I use exceptions in C#? A. Yes. B. No. C. D. ANSWER : Option A Yes. In fact exceptions are the recommended error-handling mechanism in C#. Q.4 Which of the following statement are correct about exception handling in c#.net? Page 1

2 I. If our program does not catch an exception then the.net CLR catches it. II. It is possible to create user defined exception. III. All types of exception can be caught using the Exception class. IV. CLR Exceptionsis the base class for all exception classes. V. For every try block there must be a corresponding finally block. A. I and II. B. I, II and III. C. IV and V. D. All the above ANSWER : Option B I, II and III. When an exception is thrown, the common language runtime (CLR) looks for the catch statement that handles this exception. If the currently executing method does not contain such a catch block, the CLR looks at the method that called the current method, and so on up the call stack. If no catch block is found, then the CLR displays an unhandled exception message to the user and stops execution of the program. If you want users to be able to programmatically distinguish between some error conditions, you can create your own user-defined exceptions. The.NET Framework provides a hierarchy of exception classes ultimately derived from the base class Exception. Each of these classes defines a specific exception, so in many cases you only have to catch the exception. You can also create your own exception classes by deriving from the Exception class. When creating your own exceptions, it is good coding practice to end the class name of the user-defined exception with the word "Exception." C# exceptions are represented by classes. The exception classes in C# are mainly directly or indirectly derived from the System.Exception class. Some of the exception classes derived from the System.Exception class are the System.ApplicationException and System.SystemExceptionclasses.The System.ApplicationException class supports exceptions generated by application programs. So the exceptions defined by the programmers should derive from this class. The System.SystemException class is the base class for all predefined system exception. Q.5 Which of the following statements are correct about exception handling in C#.NET? I. If our program does not catch an exception then the.net CLR catches it. II. It is possible to create user-defined exceptions. III. All types of exceptions can be caught using the Exception class. IV. CLR Exceptions is the base class for all exception classes. V. For every try block there must be a corresponding finally block. Page 2

3 A. Iand II only B. I, II and III only C. IV and V only D. All of the above ANSWER : Option B I, II and III only When an exception is thrown, the common language runtime (CLR) looks for the catch statement that handles this exception. If the currently executing method does not contain such a catch block, the CLR looks at the method that called the current method, and so on up the call stack. If no catch block is found, then the CLR displays an unhandled exception message to the user and stops execution of the program. Q.6 Which of the following is NOT a.net Exception class? A. Exception B. StackMemoryException C. DivideByZeroException D. OutOfMemoryException ANSWER : Option B StackMemoryException Because the heap memory is controlled by memory management of.net. Q.7 Which of the following are properties of Exception Type? A. Message B. Source C. StackTrace D. All the above ANSWER : Option D All the above Message : This is a short description of the exceptions cause. Message is a read only string property. Source : This is the application name. source is a string property that can be assigned to or read from. StackTrace : This is the path through the compiled programs method hierarchy that the exception was generated from. Q.8 Does the System.Exception class have any cool features? A. Yes. B. No. C. D. Page 3

4 ANSWER : Option A Yes. The feature which stands out is the StackTrace property. This provides a call stack which records where the exception was thrown from. Q.9 Can we have multiple catch blocks with try block? Try //Code that can generate exception Catch(System.DivideByZeroException ex) //code to handle the divide by zero exception Catch(system.ArithmaticException ex) // Code to handle the arithmatic exception A. Yes B. No C. D. ANSWER : Option A Yes Yes we can have as any number of catch blocks with a try block Though each catch block should catch a different exception. The order of catch block is important,because the catch block are examined in order. User should always catch the more specific exception before than the less specific one.the compiler will produce an error if order your catch block so that a later block will never be reached. Try //Code that can generate exception Catch(System.Exception ex) //code to handle the divide by zero exception Catch(system.ArithmaticException ex) // Code to handle the arithmatic exception The above code will produce a compile time error^aeur Page 4

5 Q.10 What would be the output of following code snippet? Try A==10/0; Console.WriteLine(a); Catch (System.DivideByZeroException ex) Console.WriteLine(^aEURoedivide by zero exception^aeur Q.11 Which of the following statements are correct about exception handling in C#.NET? I. If an exception occurs then the program terminates abruptly without getting any chance to recover from the exception. II. No matter whether an exception occurs or not, the statements in the finally clause (if present) will get executed. III. A program can contain multiple finally clauses. IV. A finally clause is written outside the try block. V. finally clause is used to perform clean up operations like closing the network/database connections. A. I only B. II only C. II and V only D. III and IV only ANSWER : Option C II and V only In that Finally is not Class, it is block. It is optional also to include in try catch. But when use Try statement, at least one catch statement should present. Throw will also option, it is used only user want to throw user exception. Q.12 Which of the following options is a C#.NET exception class? (Multiple Choice) A. ArithmeticException & ArrayTypeMismatchException. B. DivideByZeroException & IndexOutOfRangeException. C. InvalidCastException & NullReferenceException. D. All the above. ANSWER : Option D All the above. We have few more common exception classes such as Exception, Stack Overflow Exception and Type Initialization Exception. Q.13 Is the following true about stack trace? A. Gets a string representation of the immediate frames on the call stack. Page 5

6 B. It is commonly used during interactive and post-mortem debugging. It can also be to the user of a program as part of an error message,which a user can report to a programmer. C. A stack trace allows to track the sequence of nested functions called up to the point where the stack trace is generated. In a post-mortem scenario this is up to function where the failure occurred. D. All of the above. ANSWER : Option D All of the above. Stack Trace is a property of exception object. The stack trace property lists method calls in reverse chronological order,that is, the most recent method call is described first, and one line of stack trace information is listed for each method call on the stack.however,the stack trace property might not report as many method calls as expected due to code transformations that occur during optimization. Q.14 Select which among is NOT an exception? A. Stack Overflow B. Arithmetic Overflow or underflow C. Incorrect Arithmetic Expression D. All of the above mentioned ANSWER : Option C Incorrect Arithmetic Expression The CLR is being run in a hosted environment where the host specifically allows for StackOverflow exceptions to be handled. The stackoverflow exception is thrown by user code and not due to an actual stack overflow situation.arith^a-metic oper^a-a^a-tions and con^a-ver^a-sions in C# are exe^a-cuted in an unchecked con^a-text. This means that for a signed inte^a-ger it over^a-flows from int.maxvalue to int.minvalue and under^a-flows from int.minvalue to int.maxvalue, hence both state^a-ments below eval^a-u^a-ates to true: (int.minvalue ^aeur" 1) == int.maxvalue; (int.maxvalue + 1) == int.minvalue; Sim^A-i^A-larly, for an unsigned inte^a-ger it will under^a-flow from 0 to uint.maxvalue and over^a-flow from uint. MaxValue to 0: (0 ^aeur" 1) == uint.maxvalue; // uint.minvalue = 0 (uint.maxvalue + 1) == 0; Q.15 In C#.NET if we do not catch the exception thrown at runtime then which of the following will catch it? Page 6

7 A. Compiler B. CLR C. Linker D. Loader ANSWER : Option B CLR Exception occurs at runtime because clear catches. Q.16 Choose the correct output for given set of code: static void Main(string[] args) try Console.WriteLine("csharp" + " " + 1/Convert.ToInt32(0)); catch(arithmeticexception e) Console.WriteLine("Java"); Console.ReadLine(); A. Csharp. B. Java. C. Run time error. D. csharp 0 ANSWER : Option B Java. 1 / 0, hence system out of flow exception error. Q.17 Which type of exception the following code will throw? Class program Static void Main() String value = ^aeuroetest^aeur Q.18 From which base class all exceptions are derived from? A. System.Exception B. System.Error.Exception C. System.Error D. System.Fault ANSWER : Option A System.Exception Page 7

8 All exception derives from exception base class.exception can be generated programmatically or can be system.application Exception serves as the base class for all application specific exception classes. It derives from exception but does not provide any extended functionality. You should derive your custom application exception from Application Exception. Application exception is used when we want to define user defined exception,while system exception is all which is defined by.net. Q.19 Choose the correct output for given set of code: class Program static void Main(string[] args) try Console.WriteLine("csharp" + " " + 1/0); finally Console.WriteLine("Java"); Console.ReadLine(); A. csharp 0. B. Run time Exception generation. C. Compile time error. D. Java ANSWER : Option B Run time Exception generation Run time Error of division by zero. Q.20 Can I define my own exceptions? A. Yes. B. No. C. D. ANSWER : Option A Yes. just derive your exception class from Application.Exception. Page 8

9 Q.21 Is finally block mandatory with try catch blocks? A. Yes B. No C. D. ANSWER : Option B No No finally block is not mandatory with try catch blocks. Try Catch Finally However, The statements in the finally clause are guaranteed to execute following the execution of the try clause or the relevant catch clause. At first,the finally clause doesn^aeurtmt seem necessary.if you want code executed after try and catch,why cant you simply put it after the catch clause itself? The answer is simple : The try or catch clause could contain a return statement to return control to the calling method or to terminate the program. In that case the statement following the last catch clause of the try statement would not be executed. That^aEURTMs where the finally clause helps out. If the try or catch clause contains a return statement, the statement in the finally clause are guaranteed to execute regardless. Its also possible to exit a try or catch clause with a go to or a throw statement, which I will describe shortly. The statements in the finally clause execute in those cases as well. You generally use a finally clause for clean up.a finally clause might close a file,for example its possible to have clause following a try clause but with no catch clause. In this case,the user is notified of the error as if the program did not handle the exception, but the clause is executed before the program is terminated. Q.22 Exceptions is the Object-Oriented style of handling run-time errors. A. True. B. False. C. D. ANSWER : Option A True. Exception handling is an in built mechanism in.net framework to detect and handle run time errors. The.NET framework contains lots of standard exceptions. The exceptions are anomalies that occur during the execution of a program. They can be because of user, logic or system errors. If a user do not provide a mechanism to handle these Page 9

10 anomalies, the.net run time environment provide a default mechanism, which terminates the program execution. Q.23 What would be the output of following code snippet? Using System; Public class Throw Test2 Static int GetNumber(int index) Int[] nums = 300,600,900; If (index>nums.length) Throw new IndexOutOfRangeException(); Return nums[index]; Static void Main() Int result =GetNumber(4); A. 300 B. 600 C. 900 D. IndexOutOfRangeException ANSWER : Option D IndexOutOfRangeException Index passed to GetNumber Function is 4. However,maximum index which nums array can accept is 2. And we also have a check If(index >nums.length) Which means If(4 >3) So code will raise IndexOutofRangeException. Q.24 Which of the following statements is correct about an Exception? A. It occurs during compilation. B. It occurs during linking. C. It occurs at run-time. D. It occurs during Just-In-Time compilation. ANSWER : Option C It occurs at run-time. The runtime uses an exception-handling model based on exception objects and protected blocks of code. An Exception object is Page 10

11 created to represent an exception when it occurs. The runtime creates an exception information table for each executable. Each method of the executable has an associated array of exception-handling information (which can be empty) in the exception information table. Each entry in the array describes a protected block of code, any exception filters associated with that code, and any exception handlers (catch statements). This exception table is extremely efficient and does not cause any performance penalty in processor time or in memory use when an exception does not occur. You use resources only when an exception occurs. Q.25 Which of the following is the Object Oriented way of handling run-time errors? A. OnError B. HERESULT C. Exceptions D. Error codes ANSWER : Option C Exceptions When an exception occurs it firstly see by operating system.os return back it to CLR where CLR convert it to an object of that error then see if according to that exception is there any catch block which can handle that exception then OK otherwise terminates the application. Q.26 Which of these keywords must be used to monitor for exceptions? A. try B. finally C. throw D. catch ANSWER : Option A try The TRY statement takes no arguments. It is used to identify one or more Cach~A(c)MVBasic code statements between the TRY keyword and the CATCH keyword. This block of code is protected code for structured exception handling. If an exception occurs within this block of code, Cach~A(c) sets exception var to an object describing the exception, then transfers execution to an exception handler, identified by the CATCH statement. This is known as throwing an exception. If no exception occurs, execution continues with the next Cach~A(c)MVBasic statement after the END TRY statement. An exception may occur as a result of a runtime exception, such as attempting to divide by 0, or it may be explicitly Page 11

12 propagated by issuing a THROW statement. A TRY block must be immediately followed by a CATCH block. The paired TRY and CATCH are terminated by an END TRY statement. Page 12

#using <System.dll> #using <System.Windows.Forms.dll> using namespace System; using namespace System::Windows::Forms;

#using <System.dll> #using <System.Windows.Forms.dll> using namespace System; using namespace System::Windows::Forms; Lecture #13 Introduction Exception Handling The C++ language provides built-in support for handling anomalous situations, known as exceptions, which may occur during the execution of your program. Exceptions