VB Quick Reference
Programming Usable
Interfaces (05-630/05-430)
Spring 2004
[Includes material
from http://www.garybeene.com/vb/tutor.htm]
Declarations
Dim -
Used to define a variable
as a certain type. DIM is that simplest way to declare a variable.
Dim varName
as VarType
Possible
types include Integer, String, Double (floating
point), Boolean
VB
will let you leave off the VarType declaration, or let you use Object
(the equivalent was called Variant in VB6) as the type (can
store
any type). Both of these options are bad ideas: then YOU
have to
keep track of the type of the variable and make sure you do the right
thing. Uuse
types so that VB can help you find your bugs.
In
VB.Net, you can declare the variable and initialize it in one step:
Dim myInt as Integer = 42
Const - Creates a variable whose value is fixed
Const kgToPound = 2.205
Call - Transfers control to a Sub or Function (is optional)
Call Procedure 1
Since the use of CALL is optional, you can ignore this.
Sub - Defines a method which can execute a block of code
Sub methodName (var1 as VarType, var2 as VarType, var3 as VarType)
Be sure to check out HELP for how to handle Sub arguments.
Function - Declares a procedure which can return a value
Function functionName (var1 as VarType, var2 as VarType) as VarType
This is the most versatile of the Sub/Function procedure types. It can do anything a Sub can do as well as returning a value for use in an expression.
To return a value:
VB.Net return value
Operators
/ -
\ -
Integer division (truncates the answer)
^ -
Exponentiation operator
* -
Multiply
+ -
Plus
- -
Minus
= -
Equal
> -
Greater Than
< -
Less Than
<>
- Not Equal
>=
- Greater than or equal
<=
- Less than or equal
AND -
Defines a boolean value that is the AND of
two values
result =
expression1 AND expression2
OR -
Defines a boolean value that is the OR of
two values
result =
expression1 OR expression2
IS -
Determines if 2 variables reference the same object
result =
object1 IS object2
LIKE -
Determines if one string matches a pattern
result =
string LIKE pattern
More about operators
(MSDN).
Math
Math.Round - Rounds a number to a
selectable number of
decimal places
result = Math.Round
( tempvariable,2 )
Val - Returns the numerical content
of a string
result = Val
("123.4")
Int - Returns an integer by
truncating
i = int
(
tempvariable )
Math.Sqrt - Returns the square root
of a number
tempvariable1
= Math.Sqrt ( tempvariable2 )
Math summary (MSDN).
Type Conversions
CBool, CByte, CCur, CDate,
CDbl,
CDec, CInt, CLng, CSng, CStr, Cvar
See documentation
(MSDN).
Strings
VB.Net value.ToString() returns
the string representation of value
Left -
Returns the left n characters of a string
temp = Left
( teststring, 4 )
Right
- Returns the right n characters of a string
temp = Right
( teststring, 4 )
Trim -
Removes leading and trailing spaces of a string
temp = Trim
( teststring )
LTrim
- Removes only the leading spaces of a string
temp = LTrim
( teststring )
RTrim
- Removes only the trailing spaces of a string
temp = Rtrim
( teststring )
UCase
- Makes all characters upper case
temp = Ucase
( teststring )
LCase
- Makes all characters lower case
temp = Lcase
( teststring )
Mid -
Returns n characters from a string, starting a any position
temp = Mid
( teststring, 1, 4 )
Len -
Returns the length of a string (how many characters it has)
temp = Len
( teststring )
VB.Net:
Can also use temp =
teststring.Length
LSet -
Positions a string inside another, flush to the left
temp =
lset ( teststring )
RSet -
Positions a string inside another, flush to the right
temp =
rset ( teststring )
Format
- Returns a string formatted according to a user-defined format
temp =
format ( teststring, "####.0" )
String
-
temp =
left ( teststring, 4 )
Chr -
Returns the string representation of a number
temp = str
( 32 )
Asc -
Returns the ASCII code of a single character
temp = asc
( "A" )
Space
- Returns n spaces
temp =
space ( 15 )
Instr
- Determines if one string is found within a second string
i =
Instr (starthere, string1,
string2)
InStrRev
- Determine if one string is found in a second, starting at the end
i =
InStrRev (string1, string2,
start)
StrComp
- Compares two strings
result =
StrComp (string1, string2)
StrConv
- Converts the case of a string's characters
StrConv
(string, vbuppercase)
StrReverse
- Reverses character order in a string
StrReverse
(string1)
Replace
- Replaces each occurrence of a string
Replace
(bigstring,
searchstring, replacementstring)
String
function examples (MSDN)
Boolean
Expressions (MSDN)
Misc
MsgBox
- A built-in dialog box that gives a message and allows a user input
x =
msgbox "Read this!", vbokonly, "Test Message"
The
result of which button the
user clicked is saved in x.
InputBox
- A built-in dialog box that allows entry of a text string
inputbox
"Input a value!", 5
RGB -
Returns a color value by inputting the red, green, and blue parts
form1.backcolor
= RGB
(12,128,256)
Me -
Refers to the current object, usually the active form
VB.Net Debug.WriteLine(Me.Text)
Loops and Conditional
Decisions
If..Then..Else - Performs code based
on the results of a test
If
A>5 Then Print "A is
a bit number!"
For...Next
- Loops a specified number of times
For i =
1 to 5: print #1, i:
next i
For Each
... Next - Walks through a collection
For
Each X in Form1.controls:
Next X
While...Wend
- Loops until an event is false
while i
< 5: i = i +1: wend
Select
Case - Takes an action based on a value of a parameter
select case
i
case 1 :
print "it was a 1"
case 2 :
print "it was a 2"
end
select
Do...Loop
- Loops until conditions are met
do while
i < 5 : i = i + 1 : loop
Choose
- Selects and returns a value from a list of arguments
Choose
(index, "answer1",
"answer2", "answer3")
With -
Executes a series of statements on a single object
With
textbox1
.Height = 100
.Width = 500
End
With
End -
Immediately stops execution of a program
End
Stop -
Pauses execution of a program (can restart without loss of data)
Stop
Use Debug.WriteLine
to print out data values. Results are shown in the Output window while
the
program is running. You must pass WriteLine a string, so compose the
string by concatenating
other strings using the + operator.
Example: Debug.WriteLine("Value
of x: " + x.ToString)