Questions to NET and Programming in C# Part 2: 101->235 101 interface intA: one, two,three{ } 102 103 104 105 106 107 108 109 110 Which of the following statements are true for the above code? a) one ,two ,three must be c) one, two, three can be classes classes or interfaces b) Above code will generate an d) one, two, three must be error as multiple values after interfaces the : is not allowed in C# If Parent is a base class and Child is its derived class then which of the following statements is not valid? a) Parent p1=new Child(); c) Parent p1=new Parent(); b) Child c1=new Child(); d) Child c1=new Parent(); Any class that contain one or more abstract methods must be declared as a) Interface c) Static d) Private b) Abstract Which of the following are correct statements for implementing an abstract class a) public abstract void class c) abstract public ClassA ClassA b) public abstract class ClassA Which of the following methods can be called as an “operation”? //'ClassA.methodA()' : virtual or abstract members cannot be private a) public void methodA(){} c) void methodA(); b) public void methodA{} d) public void methodA(); Abstract methods holds only: a) return type c) name of method b) return statements d) Parameters A can be thought as a mould of a class c) Interface a) abstract class b) Delegates d) static class Which of the following is a valid statement to implement class B in the class A a) class A implements B c) class A:B b) class A implements class B d) class B:A Properties provide the opportunity to protect a field in a class by reading and writing to it using accessors b) False a) True using System; public class Parent{ public virtual void Count(){ Console.WriteLine("100"); } }; public class Child:Parent { public override void Count(){ 10 Console.WriteLine("1000"); 11 } 12 public static void Main(){ 13 Parent p=new Child(); 14 p.Count(); 15 } } What will be the output of the above program? [0.5] [1.0] [1.0] [1.0] [1.0] [1.0] [1.0] [1.0] [1.0] [1.5] 114 What error does the following code generates when compiled? abstract class Class { public void getNumber(); } class ClassA:Class { } a) The name of base class used c) The class ClassA must is invalid declare as abstract as the class does not implements all the methods of abstract base class b) 'Class.getNumber()' must declare a body because it is not marked abstract 115 116 [1.5] abstract class Class [1.5] { private abstract void getNumber(); } class ClassA:Class {} What error does the following code generates when compiled? a) The name of base c) The class ClassA must class used is invalid declare as abstract as the class does not implements all the methods of abstract base class b) 'Class.getNumber()' d) The abstract member cannot must declare a body be private because it is marked abstract Which of the following statements are true? [1.5] a) A class inherits all c) When an interface method is mapped onto a virtual method interface in a class, it is possible for implementations derived classes to override the provided by its base virtual method classes b) Without explicitly re- d) An explicit interface member implementing, a implementations can be abstract derived class can alter the interface mappings it inherits from its base 117 118 classes using System; public class Parent { public virtual void Display(){ Console.WriteLine("100"); } } public class Child1:Parent { public override void Display(){ Console.WriteLine("1000"); }} public class Child2:Parent { public override void Display(){ Console.WriteLine("1000"); } public static void Main() { Child1 c1=new Child1(); Child2 c2=new Child2(); Parent p=c2; c1.Display(); p.Display(); }} What will be the output of above code when compile/run? a) The code will generate c) The output of the code will an error, as the object be: p is not properly 1000 instantiated 1000 b) The code will generate d) The output of the code will be: an error, as the object 1000 c2 is not properly 100 instantiated //chương trình dư dấu ngoặc - kiểm tra mắt: bó tay using System; public class Parent { public virtual void Display(){ Console.WriteLine("100"); } } public class Child1:Parent { public override void Display(){ Console.WriteLine("1000"); } public void Display(int i){ Console.WriteLine("{0}",i); }} public static void Main() { Parent p =new Child1(); [2.0] [2.0] p.Display(); p.Display(90); 119 120 }} What will be the output of above code when compile/run? a) The code will generate c) The code will generate a an error, as the object compilation error, as parent p is not properly class does not have a instantiated display method with one argument b) The output of the code d) The output of the code will be: will be: 1000 1000 90 1000 Which of the following statements are true with respect to a [2.0] virtual method a) In a virtual method c) Because methods are invocation, the allowed to hide inherited compile-time type of methods, it is possible for a the instance for which class to contain only one the invocation takes virtual method with the place determines the same signature actual method implementation to invoke b) For every virtual method inherited by or declared in a class, there exists a most derived mplementation of the method with respect to that class What will be the output of the code below? [2.0] class Room{ public bool isEmpty(){ return (true); } } class StaffRoom: Room{ public new bool isEmpty(){ return false; } public static void Main() { Room R1 = new StaffRoom(); System.Console.WriteLine(R1.isEmpty()); } 121 122 } c) False a) True b) The code will not d) The code will not compile and compile and generate generate an error at line an error at line abstract class Class{ [2.0] public abstract void getNumber(); public abstract void getHeight(); public bool isEmpty(){return (true);} } abstract class ClassA:Class{ public abstract void getWidth(); } class ClassB:ClassA { } What changes should be done in the above code so that the code does not generate any error at compile time? a) Remove the abstract c) Add the abstract modifier for modifier for the the function Class.isEmpty() Class.getNumber(), Class.getHeight() methods b) Remove the abstract d) Implement the methods modifier for the class getNumber(),getHeight(), ClassA getWidth() in the class ClassB c) Add the abstract modifier for the class ClassB Which of the following statements are true with respect to [2.0] abstract functions? c) An overriding event a) Abstract event declaration can include a new declarations are only modifier permitted in abstract classes d) An abstract event declaration b) An overriding event specifies that the accessors of declaration must the event are virtual, but does specify the exact not provide an actual same accessibility implementation of the modifiers, type, and accessors name as the inherited event c) An overriding event declaration should not include the sealed 123 124 125 modifier class Room{ [2.5] int number=0; public bool isEmpty(){ return (number>0); } } class StaffRoom: Room{ int number=10; public new bool isEmpty(){ return (number>0); } public static void Main() { Room R1=new StaffRoom(); System.Console.WriteLine(R1.isEmpty()); StaffRoom R2=new StaffRoom(); System.Console.WriteLine(R2.isEmpty()); } } The output of above code will be: a) 0,10 d) False, True b) 10,0 e) The code will generate an error c) True, False Which of the following statements are correct? [2.5] a) Like a non-abstract c) An explicit interface member class, an abstract implementations can be class must provide abstract implementations of all members of the interfaces that are listed in the base class list b) An abstract class is d) An explicit interface member not permitted to map implementations are interface onto abstract permitted to call abstract methods methods interface IMethods [2.5] { void F(); void G(); } abstract class C: IMethods { void IMethods.F() { FF(); } void IMethods.G() { GG(); } protected abstract void FF(); protected abstract void GG(); } Consider the above code The non-abstract that derive from C will have to implement: a) F() c) GG() d) G() b) FF() 126 Using directives are provided to facilitate the use of namespaces b) False a) True 127 Namespaces are defined using _ statements c) System a) Using b) Class d) Namespace 128 Which of the following statements correctly declares a namespace? a) Namespace{ - } c) namespace Namespacename{ - } b) Namespacename{ d) public namespace - } Namespacename{ - } 129 The “using” alias directives can be used to pull out and bring into scope one component from a namespace b) False a) True 130 The _ namespace provides the classes and methods for manipulating arrays a) System.IO c) System.Array b) System.Arr d) Array 131 For multiple levels of organizations _ can be used a) Classes c) a namespace b) System namespace d) a nested namespaces 132 The namespace contains all code required to interact with the including the console output a) IO c) Class d) Namespace b) System 133 When a class is used inside its namespace, the _ of that class is used a) Qualified name c) Unqualified name b) Namespace name 134 _ keyword is used to import the classes of the namespace c) namespace a) using b) class d) import 135 The Syntax of a predefined Sort method is: a) Arraytosort.Sort() c) System.Array.Sort(Arraytosort) b) Arraytosort.Array.Sort() d) System.Array.Sort() [0.5] [0.5] [0.5] [0.5] [0.5] [1.0] [1.0] [1.0] [1.0] [1.0] 136 Classes in the Base Class Library are categorized into based [1.0] on their functionality a) Assemblies c) Application b) Directives d) Namespaces 137 The syntax for declaring array is: a) arrayname DataType[]; b) arrayname[] DataType; 138 139 namespace space1{ } namespace space2{ } What does the above code implement: a) Nested namespaces [1.0] c) d) [1.5] c) b) Multi level namespaces Within the namespace we can declare following: a) Class d) b) Another namespace e) 141 c) delegates namespace Space1{ namespace Space2{ class MyClass{ } }} The fully qualified name of class MyClass is : a) Space1.MyClass() c) b) 140 d) Space2.MyClass() Hierarchical namespaces [1.5] Interface All the mentioned options [1.5] Space1.Space2.MyCl ass() Space2.Space1.MyCla ss() namespace College.Library{ namespace Shelf{ class Book{ } } } The fully qualified name of class Book is: a) Shelf.Book() 142 DataType arrayname[]; DataType[] arrayname; b) College.Library.Book() class Test{ static void Main() { int[] Array1= {3,2,1}; int i=Array.IndexOf(Array1,3); Console.WriteLine(i); [1.5] c) d) College.Library.Shelf Book() Library.Shelf.Book() [1.5] 143 144 145 146 147 148 } } What will be the output of above code a) b) class Question{ static void Main() { int[] List= {30,20,10}; Array.IndexOf(List,30); } } What will be the output of above code a) c) d) [1.5] c) The code will generate a compile time error d) contains classes useful for [1.5] b) The _ namespace synchronization a) System c) System.Thread b) System.Threading d) System.Synchronize When the array is initialized at the same time they are created, the c# compiler determines the size of array using a) the default array size for each data type c) the number of items in the initialization list b) the compilers presetting for each data d) The number present type array in the square bracket next to the data type at the right hand side By default the compiler opens _assembly a) mscorlib.dll c) system.dll b) Cdefault.dll d) namespace.dll Which of the following statements are true? a) An array is a data structure that d) The element type of an array can be any type, contains a number of variables, which but not an array type are accessed through computed indices b) The dimension lengths are not part of e) At run-time, a value the type of the array, but rather are of an array type is established when an instance of the null or a reference to array type is created at run-time an instance of that array type c) The elements of the array are all of the different types Which of the following statements are true with respect to an Array type a) System Array is itself an array-type d) An implicit reference [1.5] [2.0] [2.0] [2.0] 191 192 Which of the following lines does the above program display? c) a) d) b) using System; [2.5] class Test{ public static void Main(){ try{ int p=10; Console.WriteLine(“enter a number”); int r=Int32.Parse(Console.ReadLine()); p/=r; } 10 catch(Exception e){ 11 Console.WriteLine(e); 12 Console.WriteLine(Console.Error); 13 } 14 } 15 } Above program is compiled and run The user enters when asked for the number Does the code at line 11 and 12 displays the same output? a) It depends upon the compiler how it c) The try block treats the console input throws an exception hence the control goes to catch block but line number 11 and 12 does not produce the same output b) The try block throws an exception d) The try block not hence the control goes to catch block throw any exception but line number 11 and 12 produce hence the control the same output does not enter catch block hence lines 11 and 12 outputs nothing How can we create the object dynamically in C#? [2.5] a) C# does not allow instantiation c) By using the of objects at run time System.Activator CreateInstance() method to create an instance of object in the following manner Type b) By using the System.Reflection CreateInstance() method to create an instance of object in the following manner Type myObjectType = Type.GetTypeFromProgID ("MyDll.MyObjectName") object myObject = System.Reflectrion CreatInstance(myObjectType) myObjectType =Type.GetTypeFro mProgID ("MyDll.MyOName" ) object myObject = System.Activator.C reatInstance (myObjectType) d) In C#, Object cannot be instantiated at run time but a method of a class can be invoked [2.5] 193 using System.Reflection; using System; class Reflect { public int i=20; public char ch='a'; public float f1=10; public void GetFloat(){ Console.WriteLine(f1); } public void GetInt(){ Console.WriteLine(i); } public void GetChar(){ Console.WriteLine(ch); } } class TCPReflection { public static void Main() { Reflect sender = new Reflect(); Type t = sender.GetType(); MemberInfo [] members = t.GetMembers(); MethodInfo [] method = t.GetMethods(); FieldInfo [] f1=t.GetFields(); Console.WriteLine("No of memebers:"+members.Length); Console.WriteLine("No of fields:"+f1.Length); } } What will be the output of above code when compiled/run? //default có member: GetHashCode, Equals, tostring,getType,Ctor //field la thuoc tinh //methods: con` lai khong bao gom CTOR a) The code will generate a compile time c) The output of error above code will be: No of members : 11 No of fields: b) The output of above code will be: d) The output of above No of members : 11 code will be: No of fields: No of members : 12 No of fields: 194 Delegates help to call a method at runtime? b) False a) True 195 Indexers can have user-defined names a) True b) False 196 Subscribing an object to an event depends on whether the event exists or not b) False a) True 197 An instance of a delegate type encapsulates one or more callable entities a) True b) False 198 The object that notifies the other objects, about events is known as the publisher b) False a) True [0.5] [0.5] [0.5] [0.5] [0.5] 199 200 201 202 203 204 205 206 The type of event declaration must be of _ type a) Delegate c) Event b) Indexers d) Constructor Clients can attach executable code for events by supplying a) delegates c) event handler b) throw statements d) event subscribers Which of the following is a correct statement that defines a delegate? a) private void MyDelegate() ; d) public int MyDelegate() ; b) private delegate int MyDelegate() ; e) public delegate void MyDelegate(a,b) ; c) public delegate void MyDelegate() ; Return type of indexers is a) same as type of set method of a c) by default set to the property type of index used b) same as return type of get method d) by default set to an int data type of a property Which of the following is the correct syntax for declaring an indexer a) protected int this[int var1] c) public int this(int var1) b) public int classname[int index] d public int this[int ) var1] A delegate is a class derived from _ c) System.Class.Deleg a) System.Delegate ate b) System.Reflection.Delegate d) Delegate Class Which of the following is the correct sequence to handle an event in C# ? Subscribe object Notify subscriber Define an event a) 1, 2, c) b) 3, 2, d) Which of the following is a correct event that is named “ MyDelegate” a) public event MyDelegate MyEvent(); c) b) 207 public event MyDelegate MyEvent; C# code can be classified into types: a) Managed code b) Unmanaged code [1.0] [1.0] [1.0] [1.0] [1.0] [1.0] [1.0] 2, 3, 3, 1, based on the delegate [1.0] private event MyDelegate MyEvent(); d) public MyDelegate MyEvent; [1.0] c) d) Unsafe code Safe code 208 209 210 _ is a member that enables an object or class to provide [1.0] notifications a) A Delegate c) An Event b) An Indexers d) A constructor Statement I: Indexers should be used only in situations where the [1.5] abstraction makes sense Statement II: Indexers should have both a getter and setter, as arrays are read/write objects a) Statement I is true c) Both the statements are true d) Both the statements b) Statement II is true are false Statement I: A property can be a static member, whereas an [1.5] indexer is always an instance member Statement II: A get accessor of an indexer corresponds to a method with no parameters Which of the above statements are true? a) Statement I is true 211 212 c) Both the statements are true d) Both the statements b) Statement II is true are false For defining the delegate which of the following entities must be [1.5] specified? a) name of the each method c) return types of each method b) access modifier of each method d) parameters used by each method class Test{ [1.5] delegate void SimpleDelegate(); static void F() { System.Console.WriteLine(“Test.F”); } static void Main() { SimpleDelegate d = new SimpleDelegate(F); d(); } 10 } What will be the output of above code when compiled/run? a) The code will generate a compile time c) The code will error at line as no parameters are generate a runtime passed to the delegate error since null value is referenced code will b) The code will compile successfully d) The compile successfully but will not display anything on standard output A delegate instance encapsulates one or more methods, each of [1.5] which is referred to as a _ a) Delegated method c) Multi call method d) Invocable method b) Callable entity //MSDN Statement I: The new modifier is only permitted on delegates declared [1.5] within another type Statement II: The new modifier applied on delegate overrides the method for which the delegate is being used Statement III: The new modifier applied on delegates hides inherited member by the same name and the output of above code will be: Test.F 213 214 Which of the above statements are true a) Only statement II is true c) Statement III and I are true b) Statement II and III are true d) Statement II and I are true 215 To declare a web service the class must inherit from a) System.WebService c) System.Web.Service b) System.Services d System,Web ) 216 Two types of delegates are: a) Single Cast delegate c) Multi Cast delegate b) Addable delegate d) Multi level Delegate 217 Which of the following statements are true about delegates a) A delegate can be thought of as a c) It cannot be used type-safe object-oriented function for event handling pointer allows the b) It can handle only one method at a d) It invocation of a time method without the need for inner-class adapters 218 Which of the following statements are true? a) An indexer that includes the override c) The abstract modifier modifier may also include the sealed can be used on modifier indexers but not the modifier override b) An indexer element can be classified d) The overridden as variable indexer must differ from the signatures of all other indexers declared in the same [1.5] [1.5] [1.5] [2.0] class 219 220 221 class Question{ public Hashtable Directory = new Hashtable(); public string this[string Person] { get { return (string) Directory[Person]; } set { Directory[Person] = value; } } } class Test { static void Main() { Question Dir = new Question(); // Add code here } } [2.0] Two persons named SMITH and MARTIN are to be added in the directory created above To achieve this which of the following are the valid statements that can be added in the space specified in the code above? a) Directory [“S”]=”SMITH”; Directory c) Dir [“S”]=”SMITH”; [“M”]=”MARTIN”; Dir [“M”]=”MARTIN”; b) Directory [“SMITH”]=”S”; Directory d) Dir [“SMITH”]; Dir [“MARTIN”]=”M”; [“MARTIN”]; Which of the following are true with respect to delegates? //MSDN [2.0] different a) For static methods, a callable entity d) Two delegates types that consists of just a method have the same signature and return type are not considered different delegate types e) Delegate types in C# b) Delegate types are implicitly sealed are not name equivalent, but structurally equivalent c) It is not permissible to derive any type from a delegate type Which of the following statements are true? [2.0] a) For a non-multicast delegate c) For a multi-cast instance, the invocation list consists delegate, the of the delegate instance itself invocation list is formed by concatenating the b) 222 Delegates can be combined using the concatenation operators d) class Question{ delegate void Delegate(); invocation lists of the two operands of the addition operation that formed the multicast delegate Delegate can be removed from another type using the delete operator [2.0] static void Foo() { System.Console.WriteLine("Hello"); } static void Main() { Delegate d = new Delegate(Foo); Question t=new Question(); t.MultiCall(d,3); } void MultiCall(Delegate d, int count) { for (int i = 0; i < count; i++) d(); } } 223 What will be the output of above code when compiled/run? a) The code will generate a compile time c) The code will compile error as no parameters are passed to the successfully and delegate when called display following lines on the standard output: Hello Hello Hello b) The code will generate a runtime error d) The code will compile since null value is referenced successfully but will not display anything on standard output Which of the following statements correctly differentiates between delegate [2.0] and an interface? a) Delegates can be used without the c) Unlike interfaces object reference but interface cannot be delegates remain in memory forever b) In an interface the method name is d) Interface cannot be fixed, whereas with a delegate only instantiated but the signature is fixed 224 225 226 Which of the following statements re true? a) It is not permissible to derive a nondelegate class type from System.Delegate delegates can be instantiated [2.0] c) It is possible to access members of the System.Delegate type via the usual member access syntax b) System.Delegate is an interface type d) Once instantiated, that all delegate types derives delegate instances always refers to the same target object and method Assuming that I have several clients who would like to receive notification [2.0] when a particular event occurs Putting all of them in a type of delegate can help call all the clients when a particular event occurs a) Single Cast delegate c) Multi Cast delegate b) Addable delegate d) Multi level Delegate [2.0] public delegate bool DelegateName(param1,param2) Statement I: When the compiler compiles the statement above, it internally generates a new class type Statement II: When compiler compiles the statement above, it internally generates DelegateName class Which of the above statements are true? a) Both the statements are true b) Statement II is true 227 c) d) Statement I is true Both the statements are false [2.0] What is wrong with the following code? //Unsafe code may only appear if compiling with /unsafe public unsafe struct Node { public int Value; public Node* Left; public Node* Right; } a) The “unsafe” keyword should precede the public modifier in the struct declaration above b) Variables Left and Right having data type “pointer” must be declared as “unsafe” c) Nothing is wrong with the above code d) Pointers cannot be used in the struct data type 228 //Unsafe code may only appear if compiling with /unsafe [2.0] public class A { public unsafe virtual void F() { char* p; } } public class B: A { public override void F() { base.F(); } } What is wrong with the above code? a) Nothing is wrong with the above code b) 229 c) The “unsafe “ keyword must be specified d) while calling a function A.F( ) in the class B using System; class IntIndexer{ private string[] myData; public IntIndexer(int size) { myData = new string[size]; for (int i=0; i < size; i++) { myData[i] = "Empty"; } } public string this[int pos] { get { return myData[pos]; } set { myData[pos] = value; } } static void Main(string[] args) { IntIndexer myInd = new IntIndexer(5); myInd[1] = "Some Value"; myInd[4] = "Any Value"; myInd[2] = "Another Value"; Console.WriteLine("\nIndexer Output\n"); Function A.F( ) cannot be overloaded since it is declared as “unsafe” The function B.F( ) must be declared as “unsafe” [2.5] for (int i=0; i < 5; i++) { Console.WriteLine("myInd[{0}]: {1}", i, myInd[i]); } } } What will be the output of above code? a) Some Value Another Value Any Value b) 230 c) d) Some Value Any Value Another Value Empty Some Value Another Value Empty Any Value Some Value Empty Another Value Empty Any Value using System; delegate void Stereotype(); class CAmerican { public void BePatriotic() { Console.WriteLine (“America."); } } class CBrit{ public void BeXenophobic() { Console.WriteLine( "Hello" ); } } public static void Main() { CAmerican chuck = new CAmerican(); CBrit edward = new CBrit(); Stereotype[] stereotypes = new Stereotype[2]; stereotypes[0] = new Stereotype( chuck.BePatriotic ); stereotypes[1] = new Stereotype( edward.BeXenophobic ); foreach( Stereotype s in stereotypes ) s(); } } What will be the output of above code when compiled /run? a) The code generates an error as when c) The code generates an delegate Stereotype is instantiated error, as delegate [2.5] d) The code will compile successfully and output of the code will be: America Hello using System; public delegate bool MyDelegate(object sendingobj, Int32 x); public class TestDelegateClass { static bool MyFunction(object sendingobj, Int32 x) { if (x= && i < Message.Length) return Message.Substring(i,1); else return ""; } set { if(i >= && i < Message.Length) Message=Message.Substring(0,i) + value + Message.Substring(i+1); } } } What will be the output of above code? a) Code will generate a compile time error c) Code will generate a run time error [2.5] b) 234 235 The code will compile successfully and output will be: WELCOME class summing { public int total=9; public int this[int first,int second] { get { return total; } set { total=first+second; } } public static void Main(){ summing sum1=new summing(); int total=0; // add code here … } } [2.5] Which of the following code must be added to find the total of 100 and 200 and print the answer using above code? a) total= sum1[100,200]; c) sum1[100,200]=total; System.Console.WriteLine(total); System.Console.Write Line(total); b) sum1[100,200]=total; d) sum1( 100,200 )=total; System.Console.WriteLine(sum1[10,20]) System.Console.Write ; Line(sum1( 10,20 )); using System.Collections; [2.5] class Indexing{ public Hashtable Dictionary = new Hashtable(); public string this[string Name] { get { return (string) Dictionary[Name]; } set { Dictionary[Name] = value; } } } class Test { static void Main() { Indexing Index1 = new Indexing(); Index1["CA"] = "CALIFORNIA"; Index1["AM"] = "AMERICA"; System.Console.WriteLine(Index1["AMERICA"]); } } What will be the output of above code when compiled/run? a) The code will generate a compile time c) The code will compile error successfully but does not display any output b) The code will complie successfully and d) The code will compile output of code will be: successfully and AMERICA output of code will be:AM ... class summing { public int total=9; public int this[int first,int second] { get { return total; } set { total=first+second; } } public static void Main(){ summing sum1=new summing(); int total=0;... of the following is the correct syntax for declaring an indexer a) protected int this[int var1] c) public int this(int var1) b) public int classname[int index] d public int this[int ) var1] A... Main() { IndexerTest IndexMe = new IndexerTest(); IndexMe[1] = 100; IndexMe[2] = 1000; System.Console.WriteLine(IndexMe[1]); System.Console.WriteLine(IndexMe[2]); System.Console.WriteLine(IndexMe[3]);