CHAPTER 5C# .NET: Conditional Logic

Processing1

Processing2

is condition true?

true

false

CONDITION LOGIC / DECISIONS AND BRANCHING

Recall the problems we solved in week #1 & 2: we used “if (n1 > n2) { … }” to check condition and branch

This chapter will cover condition logic in detail

GENERAL VIEW

if (condition){ // condition is true // processing1} else { // condition is false // processing2}

Processing1

Processing2

is condition true?

true

false

CONDITION

if (condition){ // processing1} else { // processing2}

- The result must be ‘true’ or ‘false’- Cannot use ‘0’ or ‘1’

- Eg: For the condition (n1 > n2) => Is n1 greater than n2? The result is a ‘true’ or ‘false’

CONDITION

if (condition){ // processing1} else { // processing2}

How to set condition?Use operand to compare

Eg (n1 == n2) (n1 != n2)

Operand

Description

== is the same as

!= is NOT the same as

> is greater than

< is smaller than

>= is greater than or equal to

<= is smaller than or equal to

! Not (use for boolean type only)

CONDITION

if (condition){ // processing1} else { // processing2}

With more than 1 conditionUse && for “and”:(condition1) && (condition2)

Use || for “or”:(condition1) || (condition2)

Eg (n1 >= 0) && (n2 >=0) => both n1 and n2 must be positive

Eg (n1 >= 0) || (n2 >=0) => either n1 or n2 is positive

CONDITION

Comparing Boolean type: bool buttonClicked = false; if (buttonClicked == true) { … } if ( !buttonClicked) { … } // not

buttonClicked

CONDITION

Comparing Char type: char answer = 'N'; if (answer == 'Y') { … }

CONDITION

Comparing String type: string input = ""; // empty string if (input == "exit") { … }

CONDITION Comparing String type:

string input = ""; // empty string if (input == "exit") { … }

String class has methods to do more complex checking such as Compare(), CompareTo(), StartsWith(), EndsWith(), Equals(), etc. Will cover some in Chapter 9

Good tutorial on C# string compare: http://alturl.com/tbwi

OTHER BRANCHING – IF ONLY

if (condition){ // condition is true // processing1} // No else branch

Processing1

is condition true?

true

false

OTHER BRANCHING – IF .. ELSE IF .. ELSE

if (condition1){ // condition is true // processing1} else if (condition2){ // condition1 is false and // condition2 is true // processing2}else{// condition1 is false and //condition2 is false // processing3}

Processing1

is condition1 true?

true

false

Processing2

Processing3

true

false

is condition2 true?

OTHER BRANCHING - SWITCH

switch (n1){ case 1: // processing1 break; case 2: // processing2 break; default: // processing3 break;}

Processing1

1

Processing2

Processing3

2 3

n1

OTHER BRANCHING - SWITCH

switch (n1){ case 1: case 2: // processing2 break; default: // processing3 break;}

Processing2

Processing3

1, 2 3

n1

OTHER BRANCHING - SWITCH

switch (n1){ case 1: // processing1 goto case 2; case 2: // processing2 break; default: // processing3 break;}

Processing1

1

Processing2

Processing3

2 3

n1

EXERCISE 5.1

Textbook from page 93 – 98: Part 1 if Statements Part 2 else ... if in C# .NET

EXERCISE 5.2

Textbook from page 98 – 106: Part 3 switch Statements in C# .NET Part 4 C# Operators

EXERCISE 5.3(A)

For the GUI created in Exercise 3.2: Rename all the controls to

follow proper naming convention: eg textboxOutput, buttonZero, etc

Use winword to draft the pseudo codes for all the button click methods (you may need some variables outside the methods to be accessible by all methods)

EXERCISE 5.3(B)

For the GUI created in Exercise 3.2: Create a new project:

Exercise53B Select all the controls in

Exercise32 and paste into this new project

Code and debug manually by viewing the codes

No worry: we shall use debugging tool to debug this project in chapter 6: Debugging

SUMMARY

Condition and operands if .. else if … else switch