1. The document discusses valid and invalid variable names in C# and provides examples. It also covers different types of loops in C# - for, while, do-while loops. 2. Code snippets are provided to demonstrate the syntax of each loop type. Exercises are included to practice writing for and do-while loops. 3. Key differences between loops are explained - a do-while loop will always execute the code block at least once since the check occurs at the end, while a regular while loop may not execute if the check fails initially.

1. Valid variable names?Spot the invalid variable namesint 2counter;string $myString;char Initial;class else;int __hwnd;

2. Valid variable names?int 2counter;Invalid. Names cannot begin with a number.string $myString;Invalid. Names cannot start with $char Initial;Validclass else;Invalid. “else” is a keyword.int __hwnd;Valid.

3. Chapter 6C# .NET Loops

4. What will you be learning?For loopsWhile loopsDo loops

5. What is a loop?A loop is a way to execute a piece of code repeatedly Go round and round until an end condition is met

6. Why use loops?Eg: you need to add from 0 to 10 Solution not using loop:int answer; answer = 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10; The above solution not suitable for very large numbers (says from 0 to 10000) – programmers are lazy, what would be a faster way to solve?

7. Flowchart “for” loopStart with i = 0End when i is not < 101Update i by adding 1

8. for loopfor ( ) // start, end, update conditions{ // Processing}

9. for loopfor (inti=0; i < 101; i++ ) { // Processing}

10. for (inti=0; i < 101; i++ ) Write syntax of the following for loopsFrom j = 10 until j = 1000 (inclusive), update j by 1 for each loopFrom t = 2 until t = 1000 (inclusive), update t by 2 for each loopFrom m = 5 until m = 0 (inclusive), update m by -1 for each loop

11. Exercise Part 1 – For LoopsAdd a new project to “Part 1 For Loops”Put one button and add the following codes for its click method (pg 112):

12. Exercise Part 1 – For Loops

13. Exercise Part 2Loop Start Values and Loop End Values Add a project “Part 2” to the solution

14. Do it yourself - TimeTableModify the previous projectTo add item to the listBox: listBox1.Items.Add("xxxx")To clear the listBox: listBox1.Items.Clear( );

15. break continueAdd new project to SpfChapter6 solution: “Extra – break and continue”Add a button and add codes into its Click method:for (int x=0; x < 11; x++){ if (x==5) break;MessageBox.Show(“x =”+x);}

16. break continuefor (int x=0; x < 11; x++){ if (x==5) continue;MessageBox.Show(“x =”+x);}

17. while loopwhile ( ) // End condition {}

18. while loopinti = 0;while (i < 101){// Processing :i++; // at the end}

19. do loopdo{} while ( ); // End condition// The difference between the while(){.. } and Do {..} while(); loops is that the code in a Do loop will get executed at least once, because its while part is at the end.

20. do loopinti = 0;do{// Processing :i++; // at the end} while (i < 101);

21. Part 3Modify the previous projectChange from "for" loop to "do" loop

22. SummaryA loop is a way to execute a piece of code repeatedly We shall be using loops again when we cover ArraysThere is "foreach" loop that applies for string, array and objects