1. MIS 3200 – Unit 3 What can computers do
Follow a sequence of instructions
Follow different paths of instructions based on decisions
Do things over and over again – loops
This unit focuses mainly on decisions
dealing with conditions
if statement
nesting if statements
and / or
shortcut operators

2. Basic program structures
Computers are good at doing a series of operations one after the other
One way to view this is shown here
The sequence has a starting point
There are one or more steps
Any number of steps is possible
There is a stopping point
For example
The click event methods you have been working with have a sequence of steps that start with the open { and end with the closing }
The instructions within a method are always executed top to bottom (or start to stop like you see above)

3. REALLY IMPORTANT! Common Errors
Using variables before they are declared
Using the value of a variable before it has been assigned
Outputting final results before they are calculated
Normal processing starts at the top and moves towards the bottom – ALWAYS - the only “exception” is when you are in a loop!!

4. Program structures 2 Computers need to make decisions
They do that by testing conditions
Is this person over 18?
Is this sale taking place in Ohio?
Is this package going to shipping zones 5 or 6?
Did the Bobcats beat the Miami?
Is this employee eligible for overtime pay and if they are did they work enough hours to earn it?
Is this student and MIS major or a Finance major or a Marketing major?

5. Decisions 2
Some decisions are one-sided – if the condition is true do something (B), if not just skip to the next thing (C)
One way to show this is
If the condition is true
Do the things at B
Once B is complete move to C
If the condition is false
Go directly to C
TRUE or FALSE: regardless of the condition, will you always end up at C?

6. Decisions 3 Some decisions are two-sided
Do one thing if the condition is true (B)
Do something different (C) if the condition is false
TRUE or FALSE:
Regardless of which branch you take, will you always end up at (D)?

7. Program structures 3
Computers need to do some things over and over in a loop (the technical term is iteration)
There are several ways to create loops but the most common one looks like this
test a condition
if the condition is true, do the
things at B
once finished with B go back
and test the condition again
if the condition is true go to B, if not, go to C
What do you think will happen if the condition is false from the beginning?

8. Decision making in C#
The most common structure in C# of making decisions is the if statement
One sided decision if
Two sided decision if else

9. Conditions
Conditions, or logical expressions, have only two possible value: true and false
Can be as simple as a Boolean variable (true/false)
Can be a relational expression !!

10. Relational operators
There are six types of relations that can be tested
Relationship
Relational operator
Equality ==
Inequality (not equal) !=
Greater than
>
Greater than or equal
>=
Less than
<
Less than or equal
<=

11. Relational expressions
Only have two possible values: true or false

12. Two-sided if statement
Sometimes you want to do one thing if a condition is true and something different if it is false

13. Nested if
Sometimes we need to consider two or more conditions before we can act
One approach
Put one if statement inside another so you only look at it if the first one is true
The if statement inside begins before the oen outside
This is called nesting and the second if statement can be on either the true or false side of the first if statement

14. Nested if - example
If the employee is not Hourly, you immediately skip to here
You only get to this part if the employee is an Hourly employee

15. Another approach
Nested if statements are often used when we need to test two or more conditions at the same time. Sometimes we need
All conditions to be true before we do something
Any one of several conditions to be true before we do something
C# provides a way to test more than one condition in a single if statement

16. Multiple conditions, all true
&& which is called an AND operation
Do something ONLY if all conditions are true
Don’t do it if ANY condition is false
For example, and employee is an hourly employee AND has worked more than 40 hours
In C# the AND operation is represented by &&
Both sides of the && operator must be logical conditions – they must have or produce a value of either true or false

17. Multiple conditions, at least one of which is true
|| which is called an OR operation
Do something if one or more of the conditions is true
Don’t do it if ALL conditions are false
For example, give a discount to a young person or an older person
In C# the OR operation is indicated by || (note, this symbol is normally found over the \ key on most keyboards)
Both sides of the || operator must be logical conditions – they must have or produce a value of either true or false

18. Web Controls for Decisions
Some are lists, while others are not!
NON- LIST CONTROLS
CheckBox
RadioButton
LIST CONTROLS
CheckBoxList
DropDownList
ListBox
RadioButtonList

19. Handling different controls
NON-LIST
Use CheckChanged for method name
Use .Checked in the if statement
Used with checkboxes
Values stored in .Text
LIST
Use SelectedIndexChanged for method name
Use .SelectedValue in the if statement
Used with CBL & RBL
Values stored in Items

20. RadioButtonList: Adding
Similar to RadioButtons but easier to use when you have multiple choices
Choices are represented by a series of ListItems
ListItems are created using the EditItems… option of the smart menu
An alternative to radio button lists is the standalone RadioButton. An alternative to the Check box lists is the Checkbox.
Typically used to represent two or more mutually exclusive choices (only one can be true at a time)
Each Checbox or Radiobutton has a Checked property
If the button is pushed – Checked is true
If the button is not pushed – Checked is false
By default ALL RadioButtons on a page are NOT linked to each other and any number of them can be checked
This behavior can be changed by putting the buttons in groups using the GroupName property
RadioButtons in the same group can only be checked one at a time (clicking another RadioButton in the same group will un-check any other RadioButton in the group). This behavior is automatic in a RadioButtonList, and therefore it is advantageous to use RadioButton Lists instead of standalone Radio buttons. Checkbox and CheckboxLists on the otherhand are both used.
The CheckChanged Method
The default event for a RadioButton or Checkbox is CheckedChanged
Once a RadioButton is selected it stays selected until another RadioButton in the same group is selected. This means you can’t unselect a RadioButton by clicking it. This is not the case for a standalone Checkbox. It can be selected and de=selected as needed.
And this means the CheckedChanged event only fires when the RadioButton is selected. For the checkbox it means that it fires each time the state of checking it is changed.
You need a separate CheckedChanged method for each RadioButton or Checkbox standalone items, but only one for the List Collection Items.
New RadioButtonList
Smart menu button
RadioButtonList with expanded smart menu – click on Edit Items…

21. RadioButtonList: Editing
Completed RadioButtonList with its RepeatDirection property set to Vertical
New ListItem with Text and Value set
Click to add a new ListItem
The Text property is what the user sees
Completed RadioButtonList with its RepeatDirection property set to Horizontal
The Value property is what the program sees and and the value used in decisions

22. RadioButtonList: Processing
There is only one event, a SelectedIndexChanged event, for the entire RadioButtonList
Once the event fires there are several ways to determine which button is clicked

23. Shortcut operators Shortcut operator are of two types Accumulation
A value is added to the value & stored in another variable
And the result is stored back in the same variable
Moving by one value
When the new value only changes by ONE (+1 or -1)
A little history on arithmetic operators…
C# belongs to a family of languages that began with a language called C
At the time C was created programs were written on VERY slow devices (like teletype terminals that could print at most 10 characters per second)
Because of this environment C, and all C family languages, has a number of shortcuts designed to shorten typing and printing time.
More Shortcut Operators
One shortcut was developed because programs often have statements similar to this where
A value is added to the value & stored in another variable
And the result is stored back in the same variable (this particular operation is know as accumulation)
The shortcut version of this is
The + is moved to the left of the =
The variable receiving the new value is not repeated
If we say that decTotalSales originally = 5 and decNewSale = 1 then, decTotalSales += decNewSale sets decTotalSales = 6

24. Accumulation Standard operation intCnt = intCnt + 1;
intDaysLeft = intDaysLeft – 1;
decDoubleSeries = decDoubleSeries * 2.0M;
decDiminish = decDiminish / M;
strNameList = strNameList + “, ” + strNew
shortcut
intCnt += 1;
intDaysLeft -= 1;
decDoubleSeries *= 2.0M;
decDiminish /= M;
strNameList += “, ” + strNew
It works for string concatenation (i.e. accumulation) too!

25. Adding or Subtracting by ONE
This is a simplification of Accumulation
intCnt +=1;  intCnt++;
intCnt -=1;  intCnt--;
Many shortcuts are used to do the first two operations illustrated on the previous slide: add one to (increment) or subtract one from (decrement) a variable.
This is so common that C family languages have special increment and decrement operators.
Increment and decrement operators can be used in arithmetic expressions with other operators.
Increment and decrement operators are ALWAYS written immediately next to the variable they modify with no spaces.
Increment and decrement operators can come either before or after a variable.
If they come after the variable the operation is called a “post-increment” operation.
That means that the current value of the variable is used in the equation and then the variable it is incremented (after, or post use).
If the increment operator comes before the variable the operation is called a “pre-increment (or decrement)”.
That means that one is added to (or subtracted from) the current value of the variable and the new value is used in the equation (the variable is incremented/decremented before, or pre use).
We will not use shortcut operators or increment/decrement operators very frequently but …
You will see them in sample code and examples and…
There are some places where they are very useful and you would likely have a need for them:
Concatenating to a string or Label
Controlling loops (Unit 4)

26. Try it – L1
This exercise will give you a chance to use if statements and test different conditions
Be sure ASPPub is on your desktop, open VWD and open ASPPub as your website
Select Unit3 under MIS3200 and add a new web page called yourLastNameU3L1.aspx
Click in the MainContent area and press Enter several times
In the top paragraph type UNIT 3 – L1 – USING IF STATEMENTS
If you have problems with any of this, please refer back to L1 instructions in previous units.

27. L1 #2
Convert the text to an h2 heading and make it have white letters on a dark green background
Add a table to the second paragraph. The table should have 8 rows and 3 columns
In the first row
first column, type Enter a state abbreviation
Drop a TextBox immediately after the text
Change the (ID) to txtState
Drop a button in the second column
Name the (ID) to btnState
Change the Text to Test State

28. L1 #3 Drop a Label in the third column
Change the (ID) to lblState
Clear the Text
Double-click the Test State button
Add appropriate method level comments
Add the following code within the button’s method {}
Run the page and test with different values in the text box

29. L1 #4 In the second row, first column
Type Enter a negative whole number
Drop a TextBox after the words
Change its (ID) to txtNegative
Drop a RequiredFieldValidator after the TextBox
Change the (ID) to rfvNegativeNumber
Change the ControlToValidate to txtNegative
Change the ErrorMessage to The negative number is required
Change the Text to *
Change the ForeColor to Red
Change the ValidationGroup to group1
Note: Validation controls are normally in a single group. If you want to have a few controls work together you put them in a ValidationGroup much like can place radio buttons in a group.

30. L1 #5 Drop a CompareValidator after the RequiredFieldValidator
Set the (ID) to cvNegative
Set the ControlToValidate to txtNegative
Set ErrorMessage to The negative number must be a whole number
Set the Text to *
Set ForeColor to Red
Set Operator to DataTypeCheck
Set Type on Integer
Set ValidationGroup to group1
Drop a ValidationSummary after the CompareValidator
Set the (ID) to vsNegative
Set ShowMessageBox to true
Set ShowSummary to false

31. L1 #6 In the second column of the second row
Drop a Button
Set the (ID) to btnNegative
Set Text to Test Number
Set ValidationGroup to group1
In the third column of the second row
Drop a Label
Set the (ID) to lblNegative
Clear the text
Double-click the Test Number button
Convert the contents of txtNegative to an integer
Test to see if the value is negative and display a message
(see next slide)
Related Validators, ValidationSummaries and Buttons all have to be in the same ValidationGroup

32. L1 #7 Add appropriate method level comments
Run the page and test to be sure everything is working

33. L1 #8 In the first column of the third row
Type Enter a number that is less than 18 or greater than 64
Drop a TextBox after the message
Set the (ID) to txtOrTest
In the middle column of the third row
Drop a Button
Set the (ID) to btnOrTest
Set the Text to Test Number
In the third column
Drop a Label
Set the (ID) to lblOrTest
Clear the Text
(NOTE: you would normally use Validators here to assure good data but we are omitting them for now to save time. Just remember that L3 assignments always require validation!)

34. L1 #9 Double-click the Test Number button in this row
Enter appropriate method level comments
Convert the context of txtOrTest to an integer
Test it to see if it meets the criteria and display a message
In this example we have two disconnected values that are acceptable, either less than 18 OR greater than 64, so the test we need to use is the OR operator
Verify - run the page and test to be sure you get the correct results

35. L1 #10 In the first column of the fourth row
Type Enter a number that is between 18 and 64 inclusive
Drop a TextBox after the message
Set the (ID) to txtAndTest
In the middle column of the fourth row
Drop a Button
Set the (ID) to btnAndTest
Set the Text to Test Number
In the third column
Drop a Label
Set the (ID) to lblAndTest
Clear the Text

36. L1 #11 Double-click the Test Number button in this row
Enter appropriate method level comments
Convert the context of txtAndTest to an integer
Test it to see if it meets the criteria and display a message
In this example we have a continuous range of acceptable values so the test we need to use is the AND operator
Run the page and test to be sure you get the correct results

37. L1 #12 Double check to be sure everything works
Open your MIS3200 home page and and a link to this L1 assignment
Copy ASPPub back to your ASPNET account and submit your MIS Portfolio public URL to the Unit 3.1 L1 drop box.

38. L2
Open ASPPub
Copy your xU3L1.aspx file, paste it back in the Unit3 directory and rename it yourLastNameU3L2.aspx
In the first column of row 5 of the new file
Drop a CheckBox
Set the (ID) to ckbAge
Set AutoPostBack to true
Set the Text to 18 and over
Skip the the right-most column
Drop a Label
Change (ID) to lblAge
Clear the Text
We will talk about this more during the next class, but the AutoPostBack property needs to be set to true if we want to process the CheckBox as soon as its value changes

39. L2 #2 Double-click the CheckBox
This method needs to see if the CheckBox is checked and output an appropriate message

40. L2 #3 In the first column of row 6 In the right-most column of row 6
Type Gender with Radio Buttons
Drop a RadioButton after the text
Set (ID) to rbMale
Set Text to Male
Set AutoPostBack to true and set the GroupName to gender
Drop another RadioButton after the first one
Set (ID) to rbFemale
Set Text to Female
In the right-most column of row 6
Drop a Label
Set (ID) to lblGender1
Clear the Text

41. L2 #4 Double-click rbMale
Enter code to determine if the button is checked and display an appropriate message it if is
Double-click rbFemale
Run the page and test to be sure the new row works correctly (Notice any weird behavior? How could we address it? This is typically why we will use RadioButtonLists instead of RadioButtons)

42. L2 #5 In the left-most column of row seven
Type Gender with a Radio Button List
Drop a RadioButtonList after the text
Set (ID) to rblGender
Set AutoPostBack to True
Click the smart menu (see slide 20) and select Edit Items…
Add an item with Text = Male and Value = Male and
Add a 2nd item with Text = Female and Value = Female
In the right-most column of row seven
Drop a Label
Set (ID) to lblGender2
Clear the Text

43. L2 #6 Double-click the RadioButtonList
Write code to see which button is selected and output an appropriate message
Run the page and test to see that the new code works properly (did we really need to nest the 2nd if statement? In this case, no,

44. L2 #7 In the first cell of row eight Double-click the button
Drop a Button
Set (ID) to btnClearEverything
Set Text to Clear Everything
Double-click the button
Write code that clears the Text of all the Labels and TextBoxes
Write code to set the Checked property of all CheckBoxes and RadioButtons to false (this unselects everything)
Write code to set the SelectedIndex property of the RadioButtonList to -1 (-1 indicates that no value is selected in the list)

45. L2 #8 Test everything again Link this page to your MIS3200 homepage
Copy ASPPub back to your ASPNet account and submit your MIS Portfolio public URL to the Unit 3.1 L2 drop box

46. Think About It! What does an if statement allow us to do?
What is a nested if statement?
What function is performed by these shortcut operators?
+= -= *= /=
What about relational operators?
== != > >= < <=
How are increment/decrement operators used?
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