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76 Cards in this Set

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  • Back
What is a value type?
Variables that contain their data directly in the stack instad of containing a refererence to the data stored elsewhere in memory.
What are the three general value types?
Built-in types; User-defined types; Enumerations
What base type are all value types derived from?
Describe System.SByte
1 Byte; Range: -128 to 127; Used for Signed byte values
Describe System.Byte
1 Byte; Range: 0 to 255; Used for Unsigned bytes
Describe System.Int16
Bytes:2; Range: -32768 to 32767; Used for Interoperation and other specialized uses;
Describe System.Int32
Bytes:4; Range: -2147483648 to 2147483647; Used for Whole numbers and counters.
Describe System.UInt32
Bytes:4; Range: 0 to 4294967295; Positive whole numbers and counters.
Describe System.Int64
Bytes:8; Range -9223372036854775808 to 9223372036854775807; Large whole numbers;
Describe System.Single
Bytes:4; -3.402823E+38 to 3.402823E+38; Floating point numbers
Describe System.Double
Bytes: 8; -1.79769313486232E+308 to 1.79769313486232E+308; Precise or large floating point numbers.
Describe System.Decimal
Bytes: 16; -79228162514264337593543950335 to 79228162514264337593543950335; Financial and scientific calculations requiring great precision.
What value types does the runtime optimize performance for?
Int32, UInt32 and Double.
Describe System.Char
Bytes:2; Single Unicode characters
Describe System.Boolean
Bytes:4; True/False Values
Describe System.IntPtr
Size: Platform dependent; Pointer to a memory address.
Describe System.DateTime
Size: 8 bytes; 1/1/0001 12:00:00 AM to 12/31/9999 11:59:59 PM; Moments in time.
What are all types derived from?
What should you declare a variable as if you want to be able to determine whether a value has been assigned or not?
Give an example of declaring a variable a nullable.
Dim b as Nullable(Of Boolean) = Nothing

Nullable<bool> b = null;

bool? b = null;
Declaring a variable as nullable enables which members?
HasValue and Value
How do you detect whether or not a value has been set for a Nullable type?
Use HasValue.
Give an example of using HasValue and Value members for checking a Nullable type.
If b.HasValue Then Console.WriteLine("b is {0}.", b.Value) Else Console.WriteLine("b is not set.")

if (b.HasValue)Console.WriteLine("b is {0}.", b.Value); else Console.WriteLine("b is not set.");
What is another term for User-defined types?
Where are structures stored?
On the stack.
What type is System.Drawing.Point?
Value-Type; User-defined Type; structure.
Structure types should meet the following criteria...
Logically represent a single value; Has and instance size less than 16 bytes; Will not be changed after creation; Will not be cast to a reference type.
Give an example of declaring an enumeration>
Enum Titles As Integer
End Enum

enum Titles : int{Mr, Ms, Mrs, Dr};
Reference types store the address of thier data, also known as a pointer where?
On the stack.
The actual data that is stored for a reference type is stored where?
On the heap.
The runtime manages the memory used by the heap how?
By a prcoess called "Garbage Collection"
What does Garbage Collection do?
Recovers memory periodically as needed by disposing of items that are no longer referenced.
When does Garbage Collection occur?
When needed or triggered by a call to GC.Collect.
What happens when you assign a reference type to another instance of that reference type?
Both instances will point to the same memory location on the heap.
Everything not derived from System.ValueType is what?
A reference type.
Describe System.Object
Can convert any type to System.Object. Most general type in the Framework.
Describe System.String
Text Data
Describe System.Text.StringBuilder
Dynamic text data
Describe System.Array
Base class for all arrays. Arrays of data.
Describe System.IO.Stream
Buffer for file, device and network I/O. Abstract base class; task-specific classes are derived from Stream.
Describe System.Exception
Task-specific exceptions inherit from this type.
What does immutable mean?
Any change causes the runtine to create a new object and abandon the old one.
Is System.String immutable?
What happens when you append strings using + ?
Only the last string has a reference, all others will be disposed during garbage collection
How do you avoid temporary strings?
Use the Concat, Join or Format methods to join multiple items in a single statement or use the StringBuilder class.
The default constructor for StringBuilder creates a buffer size of how long?
16 bytes
Describe FileStream
Create a base stream used to write to or read from a file.
Describe MemoryStream
Create a base stream used to write to or read from memory.
Describe StreamReader
Read data from the stream
Describe StreamWriter
Write data to the stream
How should you order your catch blocks for Exception handling?
From most specific to the more generic.
From what class should you derive from when defining your own exceptions?
What should be done in the finally block for Exception handling?
closing streams or cleaning up any objects that might be left open if an exception occurs.
What is an interface?
A contract, defines a common set of members that all classes that implement the interface must provide.
Describe IComparable
Implemented by types whose values can be ordered (numeric and string classes). IComparable is required for sorting.
Describe IDisposible
Defines methods for manually disposing of an object.
Describe IConvertible
Enables a class to be converted to a base type such as Boolean, Byte, Double or String.
Describe ICloneable
Support copying an objectg
Describe IEquatable
Allows you to compare to instances of a class for equality. (a==b)
Describe IFormattable
Enables you to convert the value of an object into a specially formatted string. Provides more flexibility than the base ToString method.
Can a class implement multiple interfaces?
Can a class be inherited from multiple classes in .Net?
What are partial classes?
Allow you to split a class definition across multiple source files. It hides details of the class definition so that derived classes can focus on more significant portions.
What are generics?
Allows a user to define a type while leaving some details unspecified. Instead of specifying the types of parameters or member classes, you can all code that uses your type to specify it.
What are the advantages of using generics?
Reduced run-time errors and improved performance.
Give an example of creating a Generic Type.
class Gen<T, U>{public T t; public U u;

public Gen(T _t, U _u)
t = _t;
What is the significant limitation of creating a generic class?
generic code is only valid if it will compile for every possible constructed instanc of the generic, whether an Int, a string, or any other class.
Give an example of consuming a generic type
Gen<string, string> ga = new Gen <string, string>("Hello, ", "World!");
How do you avoid the limitation of generics of having to write code that would compile for any class?
Use constraints to place requirements on the types that consuming code can substitute for your generic.
What are the four types of constraints Generics support?
Interface - Allow only types that implement specific interfaces to use your generic.

Base Class - Allow only types that match or inherit from a specific base class to use your generic.

Constructor - Require types that use your generic to implement a parameterless constructor.

Reference or value type - Require types that use your generic to be either a reference or value type.
What do you use to apply a constraint to a generic?
As clause in VB and Where clause in C#
What is an event?
A message sent by an object to signal the occurrence of an action.
What is the object that raises an event called?
Event sender
What is the object that captures an event and responds to an event called?
Event receiver.
What is a delegate?
Holds a reference to a method. It is a function pointer or a callback.
Give an example of an event delegate declaration.
public delegate void AlarmEventHandler(object sender, EventArgs e);