CIS 199 Test 02 Review

Loops for

“For a given value X, while X is true, modify X…”

while “While X is true…”

do – while “Do these tasks, while X is true…”

foreach “For every X in this set of Y do the following…”

for Example

while Example

do while Example

foreach Example

Key Loop Details Loops are NOT guaranteed to execute at least once!

…only exception is ‘do while’

‘for’ loops require a variable, condition, and ‘step’ instruction ‘while’, ‘do while’ loops require a boolean expression ‘foreach’ loops require a collection of items

Arrays Lists Generic Collections

Files OpenFileDialog

Used to load file from location

SaveFileDialog Used to select file save location

BOTH very User friendly!

OpenFileDialog

OpenFileDialog

SaveFileDialog

SaveFileDialog

Random Numbers in C# Provided from: System.Random Is ONLY pseudo-random

Produces a finite set of values with equal probability Not truly random, follows a mathematical algorithm

Created with OR without seed value Common methods used:

Next() Next(int) Next(int, int) NextDouble()

Creating and using aRandom Object

Usage & Expected Resultsof Random Methods

Methods Actions, code to be executed May return a value, may take value (not required) Can be controlled via scope keywords Can be static

Methods &Modularizing Your Code Methods

Break out ‘steps’ Easier to test Easier to visualize

Methods &Modularizing Your CodeExample

Arrays

Arrays

Sample Questions fromBlackboard Wiki

The ‘switch’ statement can replace nested if/else. But under what conditions? When matching on a specific…

Value Type Enumeration …other data

What does a ‘break’ statement do in a loop? It stops (BREAKS) loop execution Code continues, no further loop iterations

What does a ‘continue’ statement do in a loop? Goes to the next iteration CONTINUES loop execution, by skipping current iteration

What are preconditions and postconditions for a method? PRECONDITIONS

Conditions that MUST be TRUE before method execution

POSTCONDITIONS Conditions that WILL be TRUE after method execution

What is the difference between a void method and a value-returning method? VOID Method

Returns nothing! …a void return.

Value-Returning Returns a value! …that’s not a void return.

Compare and contrast the use of pass by value against pass by reference, using key word ref versus pass by reference using keyword out. Pass by Value

Passes a copy of the value Not the object itself

Pass by Reference Passes the actual object itself

‘ref’ Causes a pass by reference on a variable

‘out’ Is used to reference a variable that the method will update

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