SUMMARY
This step-by-step article describes how to use Mathematical functions,
Type Conversion functions, and String functions that are defined in Visual Basic
.NET or Visual Basic 2005.
back to the topUse Math Functions
The functions that are used for mathematical calculations are defined
in the
System.Math class. The
Math class includes trigonometric functions, logarithmic functions,
and other common mathematical functions. The following functions are the functions
that are defined in the
Math class of the System namespace.
Note To use these functions, import the System.Math namespace to
your project by adding the following code to the top of the source code:
Imports System.Math
Abs The
Abs function returns the absolute value of the specified
number.
Abs example:
This example uses the
Abs method of the
Math
class to compute the absolute value of a number.
' Code will not compile unless it is put in a Sub or in a Function.
Dim MyNumber As Double
MyNumber = Abs(50.3) ' Returns 50.3.
MyNumber = Abs(-50.3) ' Returns 50.3.
AtanThe
Atan function returns a Double value that contains the angle. The
tangent of the angle is the specified number. A positive return value represents a counter-clockwise angle from the x-axis. A negative return value represents a
clockwise angle. Multiply the return value by 180 divided by pi (?) to convert from
radians to degrees.
Atan example:
This example uses the
Atan
method of the
Math class to calculate the value of pi.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim pi As Double
pi = 4 * Atan(1) ' Calculate the value of pi.
CosThe
Cos function takes an angle in radians as an argument
and then returns a Double value that is the cosine of the specified angle.
Cos
example:
This example uses the
Cos method of the
Math class to return the
cosine of an angle.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyAngle, MySecant As Double
MyAngle = 1.3 ' Define angle in radians.
MySecant = 1 / Cos(MyAngle) ' Calculate secant.
ExpThe
Exp function returns a Double value that contains
e (the base of natural logarithms) raised to the specified power.
Use the
Pow method to calculate powers of other bases.
Exp is the inverse of
Log.
Exp example:
This example uses the
Exp method of the
Math
class to return
e raised to a power.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyAngle, MyHSin As Double
' Define angle in radians.
MyAngle = 1.3
' Calculate hyperbolic sine.
MyHSin = (Exp(MyAngle) - Exp(-1 * MyAngle)) / 2
LogThe
Log function returns a Double value that contains the logarithm of a
specified number. This method is overloaded and can return either the natural
(base e) logarithm of a specified number or the logarithm of a specified number
in a specified base.
Log example:
This example uses the
Log method
of the
Math class to return the natural logarithm of a number.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyAngle, MyLog As Double
' Define angle in radians.
MyAngle = 1.3
' Calculate inverse hyperbolic sine.
MyLog = Log(MyAngle + Sqrt(MyAngle * MyAngle + 1))
Round The
Round function returns a Double value that contains the
number that is nearest the specified value. Additional Round functions are available as
methods of the intrinsic types such as the
Decimal.Round method.
Round
example:
This example uses the
Round method of the
Math class to round a
number to the nearest integer.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyVar1 As Double = 2.8
Dim MyVar2 As Double
MyVar2 =Round(MyVar1) ' Returns 3.
Sign The
Sign function returns an integer value that indicates the sign of a
number. The following table shows the input arguments of the function and of the
return values:
Specified Number | Return Value |
Positive | 1 |
Negative | -1 |
Zero | 0 |
Sign example:
This example uses the
Sign method of the
Math class to determine the sign of a number.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyVar1, MyVar2, MyVar3 As Double
Dim MySign As Integer
MyVar1 = 12
MyVar2 = -2.4
MyVar3 = 0
MySign = Sign(MyVar1) ' Returns 1.
MySign = Sign(MyVar2) ' Returns -1.
MySign = Sign(MyVar3) ' Returns 0.
Sin The
Sin function takes an angle in radians as an argument
and then returns a Double value that specifies the sine of the angle.
Sin
example:
This example uses the
Sin method of the
Math class to return the
sine of an angle.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyAngle, MyCosecant As Double
MyAngle = 1.3 ' Define angle in radians.
MyCosecant = 1 / Sin(MyAngle) ' Calculate cosecant.
SqrtThe
Sqrt function returns a Double value that specifies the
square root of the specified number.
Sqrt example:
This example uses
the
Sqrt method of the
Math class to calculate the square root of a number.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MySqr As Double
MySqr = Sqrt(4) ' Returns 2.
MySqr = Sqrt(23) ' Returns 4.79583152331272.
MySqr = Sqrt(0) ' Returns 0.
MySqr = Sqrt(-4) ' Returns NaN (not a number).
Tan The
Tan function returns a Double value that contains the
tangent of the specified angle. The
Tan function takes an angle that is measured in
radians as the argument. When the angle that is specified is NaN, NegativeInfinity, or
PositiveInfinity, this method returns NaN.
Note Multiply by ?/180 to convert degrees to radians.
Tan
example:
This example uses the
Tan method of the
Math class to return the
tangent of an angle.
' Code is not compiled unless it is put in a Sub or in a Function.
Dim MyAngle, MyCotangent As Double
MyAngle = 1.3 ' Define angle in radians.
MyCotangent = 1 / Tan(MyAngle) ' Calculate cotangent.
back to the
topUse Type Conversion Functions
The process of changing a value from one data type to another
data type is named conversion. Conversions are either widening or narrowing,
depending on the data capacities of the types that are involved. Widening conversion and
narrowing conversion are both supported by the common language runtime. For
example, the value that is represented as a 32-bit signed integer can be
converted to a 64-bit signed integer. This is an example of a widening
conversion. The opposite conversion (from 64-bit to 32-bit) is an example of a
narrowing conversion. Information is never lost as a result of a widening
conversion. However, information may be lost as a result of a narrowing conversion.
The following Type Conversion functions are defined in Visual Basic
.NET or in Visual Basic 2005:
CBoolThe
CBool function is used to convert string expressions or numeric
expressions to Boolean values. When an expression evaluates to a non-zero value,
then the
CBool function returns True. Otherwise, the function returns
False.
CBool example:
Dim A, B, C As Integer
Dim Check As Boolean
A = 5
B = 5
Check = CBool(A = B) ' Check is set to True.
C = 0
Check = CBool(C) ' Check is set to False.
CByte The
CByte function converts a specified number to a byte. The
input argument must be a number between 0 and 255. Otherwise, you receive a
System.OverflowException.
CByte example:
Dim MyDouble As Double
Dim MyByte As Byte
MyDouble = 125.5678
MyByte = CByte(MyDouble) ' MyByte is set to 126.
CCharThe
CChar function converts only the first character of the
specified String. The input argument to
CChar must be a data-type string. You
cannot use
CChar to convert a number to a character because
CChar cannot
accept a numeric data type.
CChar example:
This example uses the
CChar function to convert the first character of a string expression to a
Char type.
Dim MyString As String
Dim MyChar As Char
MyString = "BCD" ' CChar converts only the first character of the string.
MyChar = CChar(MyString) ' MyChar is set to "B".
CDateCDate accepts any valid representation of a date and a
time and then converts to a Date.
CDate example:
This example uses the
CDate function to convert strings to Date values.
Dim MyDateString, MyTimeString As String
Dim MyDate, MyTime As Date
MyDateString = "February 12, 1969"
MyTimeString = "4:35:47 PM"
' ...
MyDate = CDate(MyDateString) ' Convert to Date data type.
MyTime = CDate(MyTimeString) ' Convert to Date data type.
CDbl The
CDbl function is used to convert a numeric expression
to a Double value. The input argument of the function must be between
-4.94065645841247E-324 and -1.79769313486231E+308 for negative values. The input argument of the function must be between 1.79769313486231E+308 and 4.94065645841247E-324 for positive
values.
CDbl example:
Dim MyDec As Decimal
Dim MyDouble As Double
MyDec = 234.456784D ' Literal type character D makes MyDec a Decimal.
MyDouble = CDbl(MyDec * 8.2D * 0.01D) ' Convert result to a Double.
CDec The
CDec function converts a numeric value to a decimal.
CDec example:
Dim MyDouble As Double
Dim MyDecimal As Decimal
MyDouble = 10000000.0587
MyDecimal = CDec(MyDouble) ' Convert to Decimal.
CInt The
CInt function converts a numeric value to an integer.
CInt example:
Dim MyDouble As Double
Dim MyInt As Integer
MyDouble = 2345.5678
MyInt = CInt(MyDouble) ' MyInt is set to 2346.
CLng The
CLng function takes a numeric value as an argument and
then returns a Long value.
CLng example:
Dim MyDbl1, MyDbl2 As Double
Dim MyLong1, MyLong2 As Long
MyDbl1 = 25427.45
MyDbl2 = 25427.55
MyLong1 = CLng(MyDbl1) ' MyLong1 contains 25427.
MyLong2 = CLng(MyDbl2) ' MyLong2 contains 25428.
CObj The
CObj function converts a numeric value to an Object.
CObj example:
Dim MyDouble As Double
Dim MyObject As Object
MyDouble = 2.7182818284
MyObject = CObj(MyDouble) ' Double value is pointed to by MyObject.
CShort The
CShort function converts a numeric value to
Short.
CShort example:
Dim MyByte as Byte
Dim MyShort as Short
MyByte = 100
MyShort = CShort(MyByte) ' Convert to Short.
CSng The
CSng function converts the numeric value to Single.
CSng example:
Dim MyDouble1, MyDouble2 As Double
Dim MySingle1, MySingle2 As Single
MyDouble1 = 75.3421105
MyDouble2 = 75.3421567
MySingle1 = CSng(MyDouble1) ' MySingle1 is set to 75.34211.
MySingle2 = CSng(MyDouble2) ' MySingle2 is set to 75.34216.
CStr The following table shows the input arguments and the return
values of the
CStr function:
Input Argument Data Type | Return Value |
Boolean | A string that contains True or False |
Date | A string that contains a Date value (date and time)
in the short date format of your system |
Numeric Value | A string that represents the number |
CStr example:
This example uses the
CStr function to
convert a numeric value to a string.
Dim MyDouble As Double
Dim MyString As String
MyDouble = 437.324
MyString = CStr(MyDouble) ' MyString is set to "437.324".
back to the topUse String Functions
The String functions are defined in different classes. The classes include
the
Microsoft.VisualBasic.Strings class and the
System.String class.
back to the topUse String Functions in the Microsoft.VisualBasic.Strings Class
The following functions are the String functions that are defined in the
Microsoft.VisualBasic.Strings class.
Note To use the String functions, import the namespace
Microsoft.VisualBasic.Strings to your project by adding the following code at
the beginning of the source code:
Imports Microsoft.VisualBasic.Strings
Asc and
AscWThe
Asc function and the
AscW function return an integer value
that represents the character code that corresponds to the specified character. The
functions accept any valid Char expression or String expression as an argument. When a
string is the input argument, only the first character of the string is used for
input. When the string contains no characters, an ArgumentException error occurs.
Asc returns the code point or the character code for the input character. The
return value can be between 0 and 255 for single-byte character set (SBCS)
values. The
return value can be between -32768 to 32767 for double-byte character set (DBCS) values.
AscW returns the Unicode code point for the input character that can be
between 0 and 65535.
Example:
Dim MyInt As Integer
MyInt = Asc("A") ' MyInt is set to 65.
MyInt = Asc("a") ' MyInt is set to 97.
MyInt = Asc("Apple") ' MyInt is set to 65.
Chr and
ChrWThe
Chr function and the
ChrW function return the character that is associated
with the specified character code. When CharCode is outside the range of -32768
through 65535, then an ArgumentException error occurs.
Example:
This example uses the
Chr function to return the character that is associated with
the specified character code.
Dim MyChar As Char
MyChar = Chr(65) ' Returns "A".
MyChar = Chr(97) ' Returns "a".
MyChar = Chr(62) ' Returns ">".
MyChar = Chr(37) ' Returns "%".
GetChar The
GetChar function returns a Char value that represents the character
from the specified index in the specified string. When the index is less than 1 or
greater than the index of the last character in the specified input argument, an
ArgumentException occurs.
Example:
This example shows how to use the
GetChar function to return a character from a specified index in a string.
Dim myString As String = "ABCDE"
Dim myChar As Char
myChar = GetChar(myString, 4) ' myChar = "D"
InStr The
InStr function returns an integer that specifies the start
position of the first occurrence of one string that is in another string.
Example:
The following example uses the
InStr function to return
the position of the first occurrence of one string that is in another string:
Dim SearchString, SearchChar As String
Dim MyPos As Integer
SearchString ="XXpXXpXXPXXP" ' String to search in.
SearchChar = "P" ' Search for "P".
' A textual comparison starting at position 4. Returns 6.
MyPos = InStr(4, SearchString, SearchChar, CompareMethod.Text)
Join The
Join function returns a string that is created by joining
substrings that are contained in an array. The one-dimensional array that contains substrings
that must be joined is passed as an argument to the
Join function. The function uses
Delimiter, String to separate the substrings in the returned strings as
an optional argument. When the Delimiter is omitted, the space character (" ")
is used as the separator between the substrings. When the Delimiter is a
zero-length string (""), the substrings in the array are concatenated with
no separators.
Example:
The following example shows how to use the
Join function:
Dim myItem(2) As String
Dim myShoppingList As String
myItem(0) = "Pickle"
myItem(1) = "Pineapple"
myItem(2) = "Papaya"
' Returns "Pickle, Pineapple, Papaya"
myShoppingList = Join(myItem, ", ")
LCase The
LCase function returns a string or a character that has been converted
to lowercase. Only uppercase letters are converted to lowercase. All
lowercase letters and non-letter characters remain unchanged.
Example:
The following example uses the
LCase function to return
a lowercase version of a string:
Dim UpperCase, LowerCase As String
Uppercase = "Hello WORLD 1234" ' String to convert.
Lowercase = LCase(UpperCase) ' Returns "hello world 1234".
LTrim,
RTrim, and
TrimThese functions return a string that contains a copy of a
specified string. When you use
LTrim, there are no leading spaces.
When you use
RTrim, there are no trailing spaces. When you use
Trim, there are no leading spaces and no trailing spaces.
Example:
The following example uses the
LTrim function to remove
leading spaces, the
RTrim function to remove trailing spaces, and the
Trim
function to remove both leading spaces and trailing spaces from a String variable:
Dim MyString, TrimString As String
MyString = " <-Trim-> " ' Initializes string.
TrimString = LTrim(MyString) ' TrimString = "<-Trim-> ".
TrimString = RTrim(MyString) ' TrimString = " <-Trim->".
TrimString = LTrim(RTrim(MyString)) ' TrimString = "<-Trim->".
' Using the Trim function alone achieves the same result.
TrimString = Trim(MyString) ' TrimString = "<-Trim->".
Replace The
Replace function returns a string where a specified
substring is replaced with another substring a specified number of times. The
return value of the
Replace function is a string that begins at the position
that is specified by the
Start argument and then concludes at the end of the specified string with
the substitutions made as specified by the values in the
Find argument and the
Replace
argument.
Example:
This example demonstrates the
Replace
function:
Dim myString As String = "Shopping List"
Dim aString As String
' Returns "Shipping List".
aString = Replace(myString, "o", "i")
StrComp The
StrComp function returns -1, 0, or 1. This is based on the result of a
string comparison. The strings are compared by alphanumeric sort values
beginning with the first character.
Example:
The following
example uses the
StrComp function to return the results of a string comparison.
When the third argument is omitted, the comparison type that is defined in the option
compare statement or the project defaults is used.
Dim MyStr1, MyStr2 As String
Dim MyComp As Integer
MyStr1 = "ABCD"
MyStr2 = "abcd" ' Defines variables.
' The two strings sort equally. Returns 0.
MyComp = StrComp(MyStr1, MyStr2, CompareMethod.Text)
' MyStr1 sorts after MyStr2. Returns -1.
MyComp = StrComp(MyStr1, MyStr2, CompareMethod.Binary)
' MyStr2 sorts before MyStr1. Returns 1.
MyComp = StrComp(MyStr2, MyStr1)
StrConvThe
StrConv function returns a string that is converted as specified in the
input arguments. The
StrConv function converts the string. The conversion is based on the value in the
Conversion argument. The value in the
Conversion argument is a member of VbStrConv
enumeration.
The
Conversion argument settings are:
Enumeration Member | Description |
VbStrConv.None | Performs no conversion |
VbStrConv.LinguisticCasing | -Uses linguistic rules for
casing instead of File System (default) -Valid with UpperCase and LowerCase
only |
VbStrConv.UpperCase | Converts the string to uppercase
characters |
VbStrConv.LowerCase | Converts the string to lowercase
characters |
VbStrConv.ProperCase | Converts the first letter of
every word in the string to uppercase |
Example:
The following example converts text to
lowercase letters:
Dim sText, sNewText As String
sText = "Hello World"
sNewText = StrConv(sText, VbStrConv.LowerCase)
Debug.WriteLine (sNewText) ' Outputs "hello world".
StrDup The
StrDup function returns a string or an object that is made up of
the specified character that is repeated the specified number of times. The
StrDup
function takes two arguments, the
Number argument and the
Character argument. The
Number argument
specifies the length to the string that must be returned by the function. The
StrDup
function uses only the first character in the
Character argument. The
Character
argument can be a Char data type, a String data type, or an Object data type.
Example:
The
following example uses the
StrDup function to return a string of duplicated
characters:
Dim aString As String = "Wow! What a string!"
Dim aObject As New Object()
Dim myString As String
aObject = "This is a String that is contained in an Object"
myString = StrDup(5, "P") ' Returns "PPPPP"
myString = StrDup(10, aString) ' Returns "WWWWWWWWWW"
myString = StrDup(6, aObject) ' Returns "TTTTTT"
StrReverse The
StrReverse function returns a string that has the character order
of a specified string reversed.
Example:
Dim myString As String = "ABCDEFG"
Dim revString As String
' Returns "GFEDCBA".
revString = StrReverse(myString)
UCase The
UCase function returns a string or a character that contains
the specified string that is converted to uppercase. Only lowercase letters are
converted to uppercase letters. All uppercase letters and non-letter characters
remain unchanged.
Example:
The following example uses the
UCase
function to return an uppercase version of a string:
Dim LowerCase, UpperCase As String
LowerCase = "Hello World 1234" ' String to convert.
UpperCase = UCase(LowerCase) ' Returns "HELLO WORLD 1234".
back to the
topUse String Functions in the System.String Class
The following are the String functions in the String
class of the System Namespace.
Note To use the String functions, import the System.String
namespace to your project by adding the following code to the beginning of the source
code:
Imports System.String
CompareThe
Compare function compares two strings that are in the
input arguments. The comparison is performed by using word sort rules. The
comparison terminates when an inequality is discovered or both strings are
compared.
Compare example:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "testexample"
s2 = "testex"
MsgBox(Compare(s2, s1)) 'Returns -1.
MsgBox(Compare(s1, s2)) 'Returns 1.
ConcatThe
Concat function concatenates one or more strings and
then returns the concatenated string.
Concat example:
The following
example shows how to use overloaded versions of
Concat:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2, sa(3) As String
sa(0) = "A"
sa(1) = "B"
sa(2) = "C"
s1 = "test"
s2 = "example"
s1 = Concat(s1, s2) 'Returns testexample.
MsgBox(s1)
MsgBox(Concat(sa)) 'Returns ABC.
CopyThe
Copy function copies the value that is in the specified string
to another string.
Copy example:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "Hello World"
'Copy the string s1 to s2.
s2 = Copy(s1)
MsgBox(s2) 'Displays Hello World.
RemoveThe
Remove function deletes a specified number of characters
from the specified string beginning at a specified position. The
Remove
function has two parameters. They are the
StartIndex parameter and the
Count parameter. The
Startindex parameter is the position in
the string that specifies where to start deleting characters. The
Count
parameter specifies the number of characters to delete.
Remove example:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "Hello World"
'Removes 3 characters starting from character e.
s2 = s1.Remove(1, 3)
MsgBox(s2) 'Displays Hello World.
SubstringThe
Substring function retrieves a string starting at the
specified position in the specified string.
Substring example:
The
following example retrieves a substring starting at a specified character
position and with a specified length:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "Hello World"
s2 = s1.Substring(6, 5) 'Returns World.
MsgBox(s2)
ToCharArrayThe
ToCharArray function copies the characters in the string to a
Unicode character array.
ToCharArray example:
The following
example copies characters at a specified position to a Character array:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1 As String
Dim ch(10) As Char
s1 = "Hello World"
'Copies the characters starting from W to d to a Character array.
ch = s1.ToCharArray(6, 5)
MsgBox(ch(3)) 'Displays l.
ToLowerThe
ToLower function takes a string argument and then returns a
copy of this string in lowercase.
ToLower example:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "Hello World"
s2 = s1.ToLower() 'Converts any uppercase characters to lowercase.
MsgBox(s2) 'Displays hello world.
ToUpperThe
ToUpper function takes a string argument and then returns a
copy of this string in uppercase.
ToUpper example:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = "Hello World"
s2 = s1.ToUpper() 'Converts any lowercase characters to uppercase.
MsgBox(s2) 'Displays HELLO WORLD.
Trim,
TrimStart, and
TrimEndThese functions return a string that contains a copy of a
specified string. When you use the
Trim function, there are no leading spaces and no trailing spaces. When you use the
TrimStart function, there are no leading spaces. When you use the
TrimEnd function, there are no trailing
spaces.
Example:
The following example uses the
TrimStart function
to remove spaces at the beginning, the
TrimEnd function to remove spaces at the
end, and the
Trim function to remove both leading spaces and trailing spaces from a String
variable:
' Code is not compiled unless it is put in a Sub or in a Function.
Dim s1, s2 As String
s1 = " Hello World "
s2 = s1.Trim() 'Returns Hello World without any white spaces.
s2 = s1.TrimStart 'Removes the spaces at the start.
s2 = s1.TrimEnd 'Removes the white spaces at the end.
back to the
top