Useful VB.NET Functions
If you are familiar with prior versions of VB.NET, you may
wonder
where all of your favorite functions and subroutines have gone. Many have been incorporated in some way or another into the classes of the .NET Framework. Many, however, are still part of VB.NET. This section
briefly
describes many common and useful VB.NET functions that you'll be using throughout the book. This section is by no means a complete reference, but it will provide some general information.
(If you're wondering where these functions are in C#, you'll find most of them built into the .NET Framework classes. You'll see their usage as we progress through this book.)
Tables 3.5, 3.6, and 3.7 introduce many of these common functions.
Table 3.5. Date/Time Functions
|
dateDiff(
dateinterval
,
date1
,
date2
[,
firstdayofweek
[,
firstdayofyear
]])
|
Returns a number specifying the number of
dateinterval
s between date1 and date2.
dateinterval
can be yyyy (year), q (quarter), m (month), y (day of year), d (day), w (weekday), ww (week), h (
hour
), n (minute), s (second).
|
|
day(
datetime
)
|
Returns an integer from 1 to 31 specifying the day of the month.
|
|
dayofweek
|
Returns an integer specifying the day of the week (0 = Sunday, 6 = Saturday); this is a property of the
datetime
data type.
|
|
hour(
time
)
|
Returns an integer from 0 to 23 specifying the hour of the day.
|
|
isdate
(
datetime
)
|
Returns a Boolean specifying if the supplied
datetime
is recognized as a valid date.
|
|
minute(
time
)
|
Returns an integer from 0 to 59 specifying the minute of the hour.
|
|
month(
datetime
)
|
Returns an integer from 1 to 12 specifying the month.
|
|
now()
|
Returns a
datetime
data type specifying the current date and time according to your computer.
|
|
second(
time
)
|
Returns an integer from 0 to 59 specifying the second of the minute.
|
|
year(
datetime)
|
Returns an integer representing the year (from 1 to 9999).
|
Table 3.6. Math Functions
|
abs(
value
)
|
The absolute value of
value
|
|
atan(
value
)
|
The arctangent of
value
|
|
cos(
value
)
|
Cosine of
value
|
|
exp(
value
)
|
e^
value
|
|
fix(
value
)
|
Returns the integer portion of a number, rounding up for negative
numbers
|
|
hex(
value
)
|
Changes base 10 to hexadecimal
|
|
int(
value
)
|
Returns the integer portion of a number, rounding down for negative numbers
|
|
log(
value
)
|
Returns the natural logarithm
|
|
oct(
value
)
|
Changes base 10 to octal
|
|
rnd
|
Returns a random number
|
|
round(
value
[,
dec
])
|
Rounds to integer, or with
dec
decimal places
|
|
sin(
value
)
|
Sine of
value
|
|
sqrt(
value
)
|
Square root of
value
|
|
tan(
value
)
|
Tangent of
value
|
Table 3.7. String Functions
|
instr([
start
, ]
string1
,
string2
[,
compare
])
|
Returns a number specifying the first position of
string2
in
string1
, or 0
otherwise
;
compare
can be 0 (
BinaryCompare
) or 1 (
TextCompare
)
|
|
left(
string
,
length
)
|
Returns a string containing a specified number of
characters
from the left side of a string
|
|
len(
string
variable
)
|
Returns a number containing the length of a string or number of bytes required to store a variable
|
|
mid(
string
,
start
[,
length
])
|
Returns a string containing a specified number of characters from another string:
Dim strstring as string = mid("hello", 3)
This returns "llo"
|
|
replace(
expression
,
find
,
replace
[,
start
[,
count
[,
compare
]]])
|
Replaces
find
in the expression with
replace
, starting at
start
;
count
is number of replacements to perform; default is -1 (all possible
replacements
);
compare
is similar to
instr
|
|
right(
string
,
length
)
|
Returns a string containing a specified number of characters from the right side of a string
|
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