| 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 | Function | Description | | dateDiff(dateinterval, date1, date2[, firstdayofweek [, firstdayofyear]]) | Returns a number specifying the number of dateintervals 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 | Function | Description | | 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 | Function | Description | | 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 | |
