CS0004: Introduction to Programming Input and Output

Review  A String is…  a sequence of characters that is treated as a single item  A String literal is surround by…  double quotes ( “” )  Typecasting is…  converting from one type to another  Explicit Typecasting Functions  CDbl(parameter) – typecasts to double  CInt(parameter) – typecasts to integer  CStr(parameter) – typecasts to string  Concatenation is…  combining multiple strings into one string  The concatenation operator is… &&

Review  Two options that should be turned on in every program you write…  Option Strict On  Option Explicit On  Some string methods and properties are…  Length  ToUpper  ToLower  Trim  Substring  IndexOf

Formatting Numbers  VB provides functions for formatting numbers to familiar forms.  Note: These all return strings  Specify the number of decimal places FormatNumber(n,r) Example: FormatNumber( , 3) returns 1,  Return in currency form FormatCurrency(n,r) Example: FormatCurrency( , 2) returns $1,  Return in a percent form FormatPercent(n,r) Example: FormatPercent(0.3452, 2) returns 34.53%

Masked Text Box  You can avoid doing data validation in some cases by forcing the user to input data in a specific form using a masked text box.  Demo  Create control  Click on the triangle on the control  Select “Set Mask”  Custom Masks  See course webpage

Date Data Type  Visual Basic also provides a date data type Dim theDate As Date  Date literals are surrounded by pound signs (#) Dim theDate As Date = #2/7/2011#  You can convert dates into strings of different formats much like the number data types FormatDateTime(theDate, DateFormat.LongDate)  See the course webpage for different date formats  Some date functions  Today  Returns today’s date  DateDiff(DateInterval.Day, date1, date2)  Returns the number of days between date1 and date2 as an integer.  See course webpage for different date intervals  theDate.AddYears(n), theDate.AddMonths(n), and theDate.AddDays(n)  Returns the date after adding n years, months, and days (respectively) to theDate.  CDate(dateString)  Typecasts the string dataString to a date data type

Date Example  New Topics:  Date date type  Date literals  Masked text box  CDate typecasting  Today function  FormatDateTime function  DateDiff function  AddDays function

Input Dialog Box  Sometimes we want to get a piece of information once and do not want to waste screen space with a text box and a label. For this we use an input dialog box. InputBox(prompt, title)  prompt is the message displayed inside of the dialog box  title is the text displayed in the title of the dialog box  This function returns the string that is in the text box in the dialog box when the user presses OK.  Thus, you want to store the result returned into a variable Dim userInput As String userInput = InputBox(“Please Enter Input”, “Input”)

Output Dialog Box  You can also display a dialog box that takes no input, but just displays a message. This is called an output dialog box. MessageBox.Show(prompt, title)  prompt and title are the same as in the input dialog box.  This displays a dialog with the message and an OK button.

Dialog Boxes Examples  New Topics  Variable scope  OnLoad event procedure  Input dialog box  Output dialog box

Named Constants  Sometimes you want to define a variable that will keep the same value throughout the running of the program. These are called constants. Const CONSTANT_NAME As Type = value  Notes:  Const makes the constant not able to take a different value after initialization  The name of the constant should be all in caps and have underscores instead of camel case for different words  You need to initialize the constant for it to have a value